Tomato Research Reportfor

2006-2007

Supported by the Florida Tomato Committee

Institute of Food and Agricultural Sciences (IFAS) 1022 McCarty HallFlorida Agricultural Experiment Station PO Box 110200Office of the Dean for Research Gainesville, FL 32611-0200

Tel: (352) 392-1784Fax: (352) 392-4965

The Foundation for The Gator Nation

MEMORANDUM

TO: The Florida Tomato Committee

FROM: George J. Hochmuth, Associate Dean for Research

SUBJECT: 2006-2007 Research Report

DATE: September 5, 2007

This report describes research by scientists in UF/IFAS/FAES that received support from the

Florida Tomato Committee during the past year. The Florida Tomato Committee support

combines with State and Federal resources to allow IFAS tomato scientists to have a strong and

productive research program focused on the tomato industry of Florida.

This is an extremely important partnership between the Tomato Industry and IFAS scientists.

We have worked together to identify the questions and needs for the industry. Together we have

prioritized the research to be accomplished. This year’s work ranged from food safety and

handling to tomato breeding and methyl bromide alternatives. Many of the results are

immediately applicable by the industry.

We hope to continue in our quest for improving production methods and product quality. We

are pleased to have the Florida Tomato Committee as a partner in programmatic support for

tomato research. On behalf of the scientists involved in tomato research, we thank you and

appreciate your support.

This report of research results is presented in electronic format. We hope you find the

information in the report useful to all facets of tomato production.

GJH:las

cc: Mark McLellan

INDEX

Research supported by FLORIDA TOMATO COMMITTEE

2006-2007 IFAS Research Reports

Page Title Investigator(s)

FOOD SAFETY AND HANDLING

1 Characterization of Genetic Mechanisms that Determine

Contamination of Tomatoes with Salmonella: from Field to the

Packing House

Max Teplitski

Keith R. Schneider

8 Refinements in the Chlorine Dioxide Gas Treatment of Tomatoes

for Controlling Microbial Contamination

Jerry A. Bartz

Keith R. Schneider

Steven A. Sargent

Jeffrey K. Brecht

METHYL BROMIDE ALTERNATIVES

11 Evaluation of Methyl Bromide Alternatives Potentially Useful in

Miami-Dade County

Waldemar Klassen

Aaron J. Palmateer

Merlyn Codallo

TOMATO BREEDING

18 Breeding Tomatoes for Florida John W. Scott

Waldemar Klassen

25 Breeding Tomatoes for Resistance to all Races of the Bacterial

Spot Pathogen

John W. Scott

Jeffrey B. Jones

30 Development of Premium Tomato Varieties with High Lycopene

and Fruity/Floral Flavor Characteristics

Elizabeth A. Baldwin

John W. Scott

Charles A. Sims

WHITEFLY AND DISEASE MANAGEMENT

36 Integrated Management of Whiteflies and TYLCV on Tomato David Schuster

Natalia Peres

48 Control of Bacterial Spot of Tomato in the Greenhouse and Field

with Kasugamycin

Kenneth L. Pernezny

Pam D. Roberts

Nikol Havranek

Nadia Abdallah

Rod Sytsma

56 Evaluating Factors Affecting Movement of the Silverleaf Whitefly

and Tomato Yellow Leaf Curl Virus

David J. Schuster

James A. Taylor

Craig D. Stanley

Jane E. Polston

Sabine Grunwald

64 Monitoring Resistance of the Silverleaf Whitefly to Insecticides David J. Schuster

Mark A. Mossler

Cover photos provided by: Phyllis R. Gilreath; Teresa Olczyk; Monica Ozores-Hampton; Steven A. Sargent; & Eric H. Simonne

Characterization of Genetic

Mechanisms that Determine

Contamination of Tomatoes

With Salmonella: From the Field

to the Packing House

Max Teplitski and Keith Schneider

Abstract

The first objective of this project was

to begin the characterization of differences

in the infection and colonizaiton of roma

and round tomatoes by a human pathogen,

Salmonella enterica. While some of the

studies are still in progress, we demonstrate

that Salmonella can colonize the interior of

tomatoes via the vascular system when taken

up through the roots. Salmonella was not

able to infect roma or round tomatoes with

intact skin, however the infection of

wounded tomatoes proceeded rapidly. Sur-

prisingly, even after 14 days of incubation,

the infected tomatoes did not show any signs

of spoilage or decay. This highlights the

need for ensuring microbiological safety of

tomatoes: even fruits with 109 cells of Sal-

monella will pass visual inspections. As we

hypothesized earlier, the infection of toma-

toes by Salmonella is an active process,

which required major virulence regulators.

The identification of these regulators now

offers an opportunity to specifically disrupt

these regulators with targeted BMP.

The second objective of the research

was to investigate potential mechanisms of

inhibiting biofilm formation by Salmonella

on surfaces, similar to those found in pack-

ing houses. By using the reporter system in

the Salmonella biofilm formation cascade,

we demonstrate that potent inhibitors of

biofilm formation are compounds producedd

by common spices, therefore these are gen-

erally recognized as safe. We followed up

on this original discovery and identified sev-

eral candidate compounds that have a potent

ability to disrupt the biofilm regulatory cas-

cade.

Introduction

This project funded by Florida To-

mato Council has two goals aimed at identi-

fying genetic mechanisms that determine the

ability of Salmonella to contaminate toma-

toes and persist as biofilms in packing

houses. Specifically, the first objective of

our proposed research focuses on the ability

of Salmonella mutants with deletions in

major virulence regulators to colonize

vegetative and reproductive organs of roma

and round tomatoes. We are also using tran-

scriptomic analysis to identify catabolic

genes that are activated during growth on

pulp of roma or round tomatoes. These ex-

periments are necessary to try to explain

why the majority of salmonellosis outbreaks

are associated with roma, and not round

commercial varieties of tomatoes. In an-

swering these questions, we also gain a

valuable insight into the dynamics and ki-

netics of tomato infection by human patho-

gens. The second objective of this proposal

is to identify activities that could disrupt

biofilm formation by Salmonella. Biofilms

are multicellular microbial aggregates that

form on biotic and abiotic surfaces and serve

as a recalcitrant, persistent reservoirs of in-

fections. The ultimate goal of this work is to

develop BMPs that specifically target and

disrupt the ability of Salmonella to contami-

nate tomatoes in the field and during proc-

essing.

The results of our studies (presented

and discussed below) contribute to helping

ensure microbiological safety of Florida

produce. We have developed an EDIS pub-

lication (http://edis.ifas.ufl.edu/SS458)

which describes sources and survival strate-

gies that human enteric pathogens rely upon

to persist on farms. The EDIS publication

also suggests management strategies for

eliminating sources of pathogens. We are

1

working on developing a similar EDIS pub-

lication, specifically for tomato growers and

processors. The data generated in the past

few months was central to our developing a

competitive USDA T-STAR proposal (the

project was highly ranked and suggested for

funding, however USDA T-STAR program

was terminated). We were able to recruit an

outstanding student, Mr. Ali Al-Agely, who

secured additional funding ($3,000) for this

project through PMCB Internship Program.

In addition to the PI’s, two other sci-

entists have contributed to this work. Part-

time technician, Mr. Dmitri Kaganov carried

out studies with Salmonella mutants. Mr.

Kaganov is a US Army veteran, and an ap-

plicant in the pre-nursing program. Mr. Ali

Al-Agely has carried studies on vascular

colonization of tomatoes, identified the con-

stitutive gfp construct and performed mi-

croscopy work described below. He is cur-

rently working on genomic analysis of bac-

terial catabolic pathways required for tomato

infection with Salmonella. Mr. Al-Agely is a

UF University Scholar, PMCB intern and a

prospective graduate student.

Current work and preliminary results

For all experiments described below,

tomato fruits were purchased from Albert-

sons or Publix. For hydroponic experiments,

segments of tomato plants were harvested in

the field and rooted in the laboratory in a

mineral Hoagland solution without use of

rooting hormones. We avoided the use of

surface-sterilized samples, exotic chemicals

or aseptically-grown plants to make sure that

normal field microflora and agrichemicals,

typically used in tomato horticulture, are

present in all our experiments.

Salmonella colonizes tomato plants

by invading the vascular system and by

multiplying in wounded fruits. Under-

standing routes of tomato infection by Sal-

monella is the first key question that we

wanted to address. To test whether wild type

S. enterica 14028 can infect tomato fruits,

saline-washed suspensions of the pathogen

were either spotted onto the intact surface of

round or roma tomatoes or spotted onto a

wound inflicted by pricking the fruit epi-

dermis with a sterile aluminum wire (1 mm

in diameter). After a week-long incubation

at 20oC, fruits were cored with a sterile core-

borer (1 cm in diameter). Cores of 3-5 cm

were recovered, epidermis was peeled off,

the rest of the core was then cut into 0.5 cm

segments. Each sample was homogenized in

sterile phosphate-saline buffer (PBS), and

then plated on XLD, a selective medium for

identification of Salmonella.

The results of these studies indicate

that Salmonella cannot infect tomato fruits

(round or roma) if the skin is intact.

Wounded tomatoes became heavily colo-

nized by the pathogen. When fruits were in-

fected with ~1,000 cells of Salmonella, after

7 days 108-10

9 colony forming units of the

pathogens were recovered. When infected

onto a wound, within a week wild type Sal-

monella was able to move and colonize up

to 10 mm of the tomato tissue. This is simi-

lar to the observation from Dr. Triplett’s

group that Salmonella and other human

pathogens readily colonize and grow within

alfalfa sprouts (Iniguez, 2005 #801). It ap-

pears, therefore, that preventing wounding

of tomatoes is tremendously important in

avoiding contamination with Salmonella.

Surprisingly, we note that tomatoes

that were infected with Salmonella did not

develop any visual symptoms typically as-

sociated with spoilage. Some of the experi-

ments with wound-infected tomatoes were

allowed to proceed for 14 days, and no signs

of spoilage were observed (data not shown) .

After 14 days of incubation, roma tomatoes

appeared wilted, while round tomatoes re-

mained turgid and did not show any symp-

toms of rot, decay or spoilage. It was sur-

prising that wounds were seldomly co-

colonized by spoilage organisms – when

2

tomato fruits samples were plated on XLD

medium only Salmonella was recovered. We

do not yet know whether Salmonella has

mechanisms of excluding other, competing

organisms or whether this is a coincidence.

Because tomatoes heavily infected with

Salmonella (up to 109 colony forming units

per sample) are indistinguishable from un-

infected fruits, it is important to avoid con-

tamination of tomatoes in order to prevent

large outbreaks of tomato-associated salmo-

nellosis.

We also tested the hypothesis that

Salmonella can infect tomatoes via the vas-

cular system. For these experiments, 15-20

cm explants of field-grown tomato plants

were rooted in Hoagland #2 solution for 2

weeks. As soon as adventious roots devel-

oped, the growth medium was seeded with

dilutions of the Salmonella inoculum. To

facilitate the identification and tracking of

Salmonella, we used a strain labeled with a

constitutively-expressed green fluorescent

protein (GFP). As shown in Fig.1, colonies

of Salmonella are clearly visible inside to-

mato roots, again consistent with the conclu-

sion of Iniguez et al., (2005) that Salmonella

are proficient endophytic colonizers.

To test whether root colonization

actually leads to translocation of the patho-

gen into above-ground parts, we developed a

“printing technique” which allows for a

quick identification of target bacteria inside

the plant tissues. Tomato stems were cut

lengthwise, from top down (to avoid cross-

contamination) and halves of stems were

printed onto XLD agar. After overnight in-

cubation, Salmonella colonies are visible on

XLD agar (Fig. 2). These results indicate

that Salmonella cannot only colonize root

tissues, but it can also be translocated into

the above-ground parts. The translocation

occured at all infection doses, and individual

salmonellae were even present in plants that

were infected with as few as 1,000 cells.

We are currently concluding our

studies on the ability of Salmonella to colo-

nize interior of fruits when infected via vas-

cular tissue or by contaminating stigmas of

flowers.

Wound infection by Salmonella is

an active process. It is unclear whether

wounding simply provides a route for entry

or whether wound exudates stimulate ex-

pression of the specific genes. The prefer-

ence of Salmonella for colonizing and in-

fecting plant wounds is similar to our obser-

vation that genes required for attachment

(the pef operon) are induced in Salmonella

during infection of sprouts (Fig. 3). The in-

volvement of the pef genes in attachment to

wounded plant tissues is similar to a better-

characterized interactions between Salmo-

nella and animal cells. For its attachment to

animal cells, Salmonella relies on extracel-

lular appendages with homologous functions

(Ledeboer et al., 2006; van der Velden et al.,

1998). The pef genes are regulated by a quo-

rum sensor SdiA (Smith and Ahmer, 2003).

As shown in Fig. 3, pefI-luxCDABE reporter

was induced during Salmonella infection of

a plant seedling in the sdiA-dependent man-

ner. The pef genes are only activated on

wounded serfaces of the seedling. This sug-

gests that Salmonella may rely on the same

virulence genes and regulators to colonize

and infect both plant and animal hosts.

Specific regulators contribute to

the ability of Salmonella to infect toma-

toes. We further tested the hypothesis that

known regulators of virulence are involved

in the ability of Salmonella to infect and

colonize tomatoes. Mechanisms controlling

virulence of Salmonella in animal models

have been well-documented, and novel

virulence mechanisms are characterized with

each new study. In this initial work, we fo-

cused on the best-characterized regulators of

virulence. A mutation in flhD, a gene re-

quired for motility and flagella production

led to 10x increase in its ability to colonize

3

fruits. Consistently with these observations,

in coinfection experiments (wild type +

mutant), however, the flhD mutant was

70±3% more proficient than the wild type in

colonizing the interior of the wounded fruit.

To further investigate the basis of this phe-

notype, we tested the phenotypes of flagel-

lated but nonmotile mutant (motA) and those

of nonflagellated mutant (fliF). The nonflag-

ellated strain behaved as the wild type, the

motA mutant with paralyzed flagella be-

haived like the flhD mutant. This indicates

that the observed phenotype is most likely

due to the presence of the flagellum itself,

not due to the regulatory functions of FlhD,

and independent of the motility.

A dramatic (10-fold) reduction in the

fitness was associated with the presence of

genes encoded by the Salmonella virulence

plasmid (pSLT-) and the ability to utilize

purine and aromatic aminoacids. A mutation

in hns (histone-like protein) also dramati-

cally reduced the ability of Salmonella to

infect tomatoes. A mutation in envZ, a sen-

sor of osmotic potential of the environment,

was not recovered from the coinfections,

suggesting, perhaps, that perceiving and re-

sponding to changes in the osmolarity are

crucial for Salmonella survival inside to-

matoes. Surprisingly, a mutation in rpoS, a

gene responsive to and controlling oxidative

stress, had no impact on the competitive

colonizaiton of the pathogen.

A deletion of hilA, a virulence

regulator abolishes hypersensitive re-

sponse. A mutant in hilA, a major regulator

of virulence and Type 3 secretion system

was at a 5x disadvantage when coinoculated

with the wild type. To further characterize

the contribution of hilA to the phenotype, the

corresponding mutant was tested for its

ability to elicit hypersensitive response in

tobacco. HilA is a major regulator of the

Type 3 secretion system encoded within

Salmonella pathogenicity island I (Bajaj et

al., 1995). HilA is central to the ability of

Salmonella to invade epithelial cells and

cause gastroenteritis (Bajaj et al., 1995).

When a suspension of the hilA mutant was

infiltrated into tobacco leaves, it did not

elicit hypersensitive response (HR) (Fig. 4).

Salmonella 14028 (wild type) elicited HR,

similar to a dedicated plant pathogen, Pseu-

domonas syringae (Fig. 4).

The second Objective of the proposal

was to focus on identifying and blocking

genes that lead to the persistence of Salmo-

nella in biofilms that form on surfaces in

packing houses. In our previous work, we

have identified several regulatory and

structural genes required for Salmonella

biofilm formation on a variety of abiotic sur-

faces. With this funding, we also discovered

that the presence of MgSO4 strongly pro-

motes biofilm formation by Salmonella. We

are investigating whether the addition of in-

expensive chelating agents may be one of

the mechanisms for disrupting the ability of

Salmonella to form biofilms on abiotic sur-

faces.

Extracts of spices and novel syn-

thetic chemicals inhibit the biofilm forma-

tion cascade. We have also screened ex-

tracts of common spices (rosemary, thyme,

ginger) and vegetables (garlic) to see

whether they contain compounds that spe-

cifically inhibit expression of genes required

for biofilm formation. The extracts of garlic

and ginger contained activities that specifi-

cally blocked expression of csrB-lacZ, a re-

porter that is tightly and specifically regu-

lated by the BarA/SirA system in Salmo-

nella enterica and biofilm formation

(Teplitski, 2006 #1003).

This is significant for several rea-

sons. BarA/SirA is a known key regulator of

both virulence and biofilm formation in all

known gamma-proteobacteria (Teplitski,

2004 #507). The discovery that spices pro-

duce compounds that block BarA/SirA de-

pendent regulation now presents an oppor-

tunity to search and identify compounds that

4

block this key regulator. Because BarA/SirA

inhibitory activity was isolated from com-

mon spices and vegetables, it indicates that

the activity is likely fit the “GRAS” (gener-

ally recognized as safe) criteria. Regulatory

approval for use of GRAS compounds in

human consumption is typically straightfor-

ward. We have initiated a collaboration with

Scripps Florida to identify synthetic inhibi-

tors of BarA/SirA, and therefore of biofilm

formation. Structures of candidate molecules

are shown in Fig. 5.

Because functional homologues of

these compounds are present in common

spices, it is likely that these compounds fit

the GRAS category and will find soon ap-

plications in food safety.

Conclusions

Our results to date indicate that:

a) Salmonella can infect tomatoes, both

round and roma, through several routes.

Salmonella can colonize roots, and cells of

Salmonella can be translocated via the vas-

cular system into aboveground parts. Salmo-

nella can infect both roma and round toma-

toes through wounds. Round tomatoes in-

fected with Salmonella appear healthy and

do not develop any visual signs of infection

for at least two weeks. Roma tomatoes tend

to wilt after 14 days of infection, although it

is not clear whether the wilting is the result

of wounding itself or the infection with Sal-

monella. Salmonella was not able to infect

roma or round tomatoes with intact skin.

b) The infection of tomatoes with Salmo-

nella is an active process, which requires

specific virulence and attachment genes.

Specific catabolic genes are required for

persistence inside the fruit. The identifica-

tion of these regulators will allow the devel-

opment of targeted BMPs for disrupting the

ability of pathogens to invade or persist

within the produce.

c) Biofilms formed by Salmonella and other

pathogens are a persistent and recalcitrant

source of infection in both the field and the

packing houses. Our screen of spices identi-

fied activities capable of inhibiting biofilm

formation. A follow-up ongoing screen

identified at least four candidate chemicals

with the potential to block biofilm formation

by Salmonella.

5

Fig. 1. Salmonella infects interior tissues of tomato roots. GFP-labeled Salmonella enterica 14028 was seeded into

the hydroponic solution. After incubation for 14 days, roots were harvested, washed, and vortexed extensively to

remove any loosely adhering bacteria. Roots and the infecting salmonellae were then visualized under the confocal

microscope. Microcolonies of Salmonella appear in green, cells walls of tomato epidermis and cortex are grey.

Fig. 2. Colonization of tomato roots with Salmonella leads to the translocation of the pathogen to above-ground

parts. When halves of the tomato stems were imprinted onto Salmonella detection medium, characteristic black

colonies indicate the presence of Salmonella inside the stems, as far as 20 cm from the roots. Even low doses of root

inoculum (103 cells/infection) led to the infection of the stems. Arrows point to the black colonies, indicative of

Salmonella. Infection doses listed at the bottom of the figure.

6

Fig. 3. pefI, a gene encoding a regulator of the fimbrial operon, is upregulated during plant colonization. Cultures of

pefI-luxCDABE reporter in sdiA+ (wild type) and sdiA- backgrounds were inoculated onto surfaces of aseptically

grown seedlings. The seedlings were incubated at room temperature, and luminescence of the sdiA-regulated pefI-

luxCDABE reporter was visualized under the Hamamtsu CCD camera. In the wild type (and not in the sdiA) back-

ground, the reporter was strongly expressed on the seedling at the infection sites (Teplitski and Ahmer,

unpublished). False color overlay indicates activation of the reporter (red>yellow>green>blue).

Fig. 4. A mutation in the virulence regulator hilA eliminates the ability of Salmonella to elicit HR, which indicates

that hilA is required for the ability of the bacteria to invade the plant. A plant pathogen, Pseudomonas syringae elic-

its HR (positive control). Negative control (buffer only) did not elicit HR. HR is an apoptosis-like plant defense re-

sponse, it appears as brown necrotic lesions. Please note, that red markings on the leaf were made with a permanent

marker to indicate sites of infection with each test strain.

Fig. 5. Structures of novel chemicals that inhibit Salmonella biofilm formation pathway.

7

Refinements in the Chlorine

Dioxide Gas Treatment of

Tomatoes for Controlling

Microbial Contamination—A

Progress Report

Jerry A. Bartz, Ph.D., Plant Pathology

Department

Keith Schneider, Ph.D., Food Science &

Human Nutrition Department

Steven A. Sargent, Ph.D., Horticultural

Sciences Department

Jeffrey K. Brecht, Ph.D., Horticultural

Sciences Department

University of Florida/IFAS Gainesville

Purpose: determine where the gas could

be applied to during commercial practice

• Concentrated on applying the gas

to fruit that had already been

boxed because:

– Fruit could be treated in

ripening rooms or trucks

– Field-packed fruit could

be treated.

• Results of initial treatments of

fruit in boxes were not encour-

aging—rates that controlled de-

cay when fruit alone were treated

in the chamber did not control

decay when fruit were enclosed

in boxes and then treated in a

sealed drum-liner plastic bag.

2.4

0.0

0.5

1.0

1.5

2.0

Stock Solution Moist Cardboard Dessicated Cardboard Cardboard in Aluminum foil Waxed Cardboard

Chamber type

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Source (ClO2)

Sink (ClO2-)

Total Cl acounted for

% of stock accounted for

Cl

(mg

) re

co

vere

d a

fter

2 h

rs.

Recovery as affected by the presence of corrugated cardboard

8

Treatment of wound-inoculated

tomatoes with 2 mg of ClO2 gas per

kg of fruit completely prevented the

development of bacterial soft rot if

the fruit were stored in a plastic

treatment chamber. By contrast,

100% percent of the control fruit de-

veloped soft rot lesions. When simi-

larly inoculated fruit were randomly

distributed among 11.3 kg of fruit in

a single commercial tomato box, the

application of up to 99 mg of ClO2

(roughly 9 mg/kg fruit) failed to re-

duce decay incidence below 50%.

Subsequently, samples of the box

enclosed in the treatment chamber

were found to inactivate up to 75%

of the chlorine dioxide that off-

gassed from an aqueous solution.

The chlorine dioxide oxidized

some of the tannins in the un-

bleached box surfaces. Conse-

quently, to treat tomatoes in a stan-

dard commercial box at an equiva-

lent of 2 mg/kg, one would have to

apply at least 10 mg ClO2/kg fruit.

Better control of bacterial soft rot in

tomatoes treated in a commercial

box was achieved by forcing more

air through the box of fruit. How-

ever, the high air-flow rate may not

be feasible in commercial packing-

houses or transportation vehicles.

Additionally, in the absence of the

cardboard, a 20 mg gas/kg fruit dos-

age was associated with severe phy-

totoxicity, which included shrinkage

of the stem scars and bleaching of

exposed corky areas. Thus, high

Treatment of tomatoes in standard tomatobox using high air-flow rates.

48/72 hrs v 10/10

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

sealed vented Average Flow + -

box treatment

% decay

Decay incidence among wound inoculated fruit treated with 4.3 mgClO2/kg for 2 hr while enclosed in a standard tomato box that is in-side a plastic drum liner. Vents on the box were sealed or not,whereas the fan was set on high. (+=inoculated fruit not treated.)

9

ClO2 doses may produce fruit quality

issues.

Because ClO2 gas is heavier than

air, uniform distribution of this gas

in a bulk container of fruit appears to

require some air movement. Whether

the air movement occurring in trucks

is sufficient is unclear. Most labora-

tory tests, including those summa-

rized above have been conducted

with a point source of ClO2 gas.

Multiple sources if properly dis-

persed above the fruit in a standard

container may reduce the amount

lost to reaction with the cardboard.

Tests are planned that will simulate

placing multiple small ClO2 produc-

ing packets on the underside of the

lid of a tomato box.

10

Evaluation of Methyl Bromide

Alternatives Potentially Useful in Mi-

ami-Dade County

Waldemar Klassen, Aaron J. Palmateer and

Merlyn Codallo

Tropical Research and Education Center Uni-

versity of Florida/IFAS

18905 SW 280 Street

Homestead, FL 33031

Currently the only registered alternative to MC-

33 (mixture of 67% methyl bromide and 33%

chloropicrin) fumigants that can be used by to-

mato growers in Miami-Dade County are

metam potassium, metam

sodium and chloropicrin, although 50%

iodomethane + 50% chloropicrin can be used

under an experimental use permit. Metam com-

pounds are somewhat erratic in their perform-

ance as soil sterilants, and the beds cannot be

planted for three weeks after treatment because

of phytotoxicity of lingering residues. Tomato

growers in Miami-Dade County are prohibited

from using 1,3-Dichloropropene/chloropicrin,

the preferred alternative elsewhere in Florida,

because there is no impervious layer separating

the root zone from the Biscayne aquifer, the

source of drinking water for Miami. 1,3-D ap-

plied in the tomato beds undoubtedly would

leach into this aquifer.

Iodomethane + chloropicrin has performed

consistently well in small plot field trials con-

ducted annually since 1995 by faculty of the

Tropical Research and Education Center. How-

ever, iodomethane + chloropicrin (MIDASR)

still lacks EPA registration. In addition the io-

domethane + chloropicrin at $10 per pound rep-

resents a ser-ious investment for growers oper-

ating on slim profit margins.

Clearly there is a need to identify several

more materials to serve as methyl bromide al-

ternatives in Miami-Dade County.

Deviation from original objectives:

1. In our original proposal, one of the

treatments listed was EDN (ethane di-

nitrile) , very promising fumigant that

has been evaluated in Australia during

the past four years. This material was to

be supplied by BOC (now part of the

Linde Group). Unfortunately the re-

quested canister of EDN has still not ar-

rived.

2. On the other hand, we were able to ob-

tain two formulations of dimethyl disul-

fide (DMDS), and we have included

these evaluations as the second study in

this project.

3. In accordance with our plans to measure

the effects of the various treatments in

suppressing the root knot nematode,

Meloidogyne incognita, we included

one sachet filled with galled tomato

roots in each plot. Unfortunately we did

not check the viability of this inoculum

just before installing the sachets in the

beds prior to treatment. When we re-

covered the sachets after the treatment,

all of the nematodes were dead even in

the untreated control. Therefore we

cannot report any data on the effective-

ness of the various treatments against

the root knot nematode.

Objectives of studies no. 1 and 2,

respectively:

In field trials of the following two sets of

treatments obtain data on efficacy against ma-

jor pathogens and pests, tomato yield and qual-

ity in order to determine the near optimum dose

rates of methyl bromide alternatives.

11

Study no. 1:

1. Shank-applied chloropicrin (PIC) at 100

pounds/acre (112.1 kg/ha) followed by

drip-applied metam potassium (KPAMR) at

60 gallons/acre (561 l./ha) + metalized

plastic mulch.

2. Preplant incorporated napropamide (Devri

nolR) at 2 pounds/acre + halosulfuron (San-

deaR) at 1 ounce/acre (70.1 gm/ha), fol-

lowed by fosthiazate (NemathorinR)

sprayed onto bed surface at 3/74 lbs/acre

(4.2 kg/ha), then shank applied chloropicrin

(PIC) at 100 pounds/acre (112.1 kg/ha) +

metalized plastic mulch.

3. Shank applied 50% iodomethane + 50%

chloropicrin (MIDASR at 150 pounds/acre

(168.1 kg/ha) + metalized plastic mulch.

4. Shank applied MC-33 at 175 lbs/acre

(196.2 kg/ha) + metalized plastic mulch.

5. Untreated control (metalized plastic mulch

only).

Study no. 2:

1. Non-treated control,

2. MC 67-33 + metalized plastic mulch.; 175

lbs acre-1

[196 kg ha-1

],

3. DMDS 100 + metalized plastic mulch.; 38

gal acre-1

[355 l ha-1

],

4. DMDS 100 + metalized plastic mulch.; 56

gal acre-1

[524 l ha-1

],

5. DMDS 100 + metalized plastic mulch.; 74

gal acre-1

[692 ha-1

],

6. DMDS 79-21 + metalized plastic mulch.;

38 gal acre-1

[355 l ha-1

],

7. DMDS 79-21 + metalized plastic mulch.;

56 gal acre-1

[524 l ha-1

], and

8. DMDS 79-21 + metalized plastic mulch.;

74 gal acre-1

[692 l ha-1

].

Note

MC-33 is a mixture of methyl bromide

(67%) and chloropicrin (33%), MIDASR is a

mixture of equal weights of iodomethane and

chloropicrin, DMDS is dimethyl disulfide,

DMDS 100 is the pure material, and DMDS

29-21 is a mixture of DMDS (79%) with chlo-

ropicrin (21%).

Materials and Methods

Site description

Both experimental sites were located at

Block 12 of the Tropical Research and Educa-

tion Center, University of Florida, Homestead,

Florida. The soil is a Krome very gravelly loam

(loamy-skeletal, carbonatic, hyperthermic

Lithic Udorthents) with 58.8% gravel (>2mm),

48.4% sand, 30.3% silt and 21.3% clay con-

tents, respectively. Soil organic carbon is from

17.8 – 26.2 g kg-1

, total nitrogen 1.1 – 1.8 g kg-

1 and soil is pH 7.6 – 8.1.

Experiment design and management

Both experiments were laid out in a ran-

domized complete block design with four repli-

cations for each treatment. Each plot consisted

of a segment of a raised bed of 39-ft (11.9 m)

in study no. 1, of and 40-ft (12.2 m) in study

no. 2. In study no. 1 and study no. 2 the treat-

ments were as described above.

For assaying the effectiveness of the treat-

ments, Fusarium oxysporum f. sp. lycopersici

and Rhizoctonia solani were increased on ster-

ile millet seed in 250 ml flasks. Flasks were

aseptically inoculated by adding a 5-mm-diam.

plug from the periphery of one-week-old cul-

tures growing on potato dextrose agar (PDA)

(Difco Laboratories, Detroit, MI). Each flask

was incubated for 7 days at 25 °C under cool-

light fluorescent illumination, and shaken daily

to thoroughly mix fungal propagules. Yellow

nutsedge tubers were procured from Azlin Seed

Service, Leland, MS. Each of these four types

of inoculum was placed in sachets formed from

nylon stocking and 100-cm long colored plastic

tape was tied to the end of each sachet with a

different color for each type of inoculum. The

sachets were loaded individually with one of

the following: 5 grams of Fusarium culture, 5

grams of Rhizoctonia culture, and 20 yellow

nutsedge tubers. The sachets containing yellow

12

nutsedge tubers were immersed in water for 24

hours. One sachet of each type was buried in

each plot at a depth of 15 cm and with the color

coded ribbon extending onto the surface of the

bed. Just before the tomato seedlings were

transplanted into the beds, the sachets were

recovered. The

F. oxysporum f. sp. lycopersici and R. solani

infested millet seeds were aseptically plated on

acidified potato dextrose agar (PDA) (Difco

Laboratories, Detroit, MI). The number of

viable colonies was counted and a percentage

of the total recovery was recorded. Percent

germination of the yellow nutsedge tubers was

recorded.

On February 21, 2007 raised beds 15-cm

high, 91-cm wide, and 182-cm between centers

were formed in a field of shallow gravelly soil.

Next, 1120 kg ha-1 of 6N:6P2O5:12K20 dry

fertilizer was rototilled into the soil, and the

raised beds were re-formed.

On March 5 and 6, 2007 the appropriate

plots on the raised beds with the above formu-

lation and at the above rates were applied in the

appropriate plots of the raised beds, with the

exception of metam potassium, which was ap-

plied through the drip lines on March 11, 2007.

Concurrent with the application of the fumi-

gants or sprays, two drip tapes (T-TAPE TSX

508-12-450, flow rate: 5.6 l/min/100 m at 5.6 m

pressure, drip spacing = 0.3 m, diameter: 16

mm; Agro Distributors, Homestead, FL) and

CanslitR metalized plastic mulch (Intergro Inc.,

Clearwater, FL) were applied. The T-tapes

connected with layflat hose for irrigation. Three

weeks after fumigation, the sachets were recov-

ered and taken to the laboratory for processing.

Immediately thereafter, tomato, cv. ‘Tygress’

seedlings (Six L Farms, Naples, FL) were

transplanted on the beds at 51 cm between

plants. For insect control, imidacloprid (Ad-

mireR) was applied through the drip tapes, and

a backpack sprayer was used to spray the plants

2 or 3 times per week with various tank mixes

containing several of the following: mancozeb

+ copper hydroxide (MankocideR), azox-

ystrobin (QuadrisR), pyriproxyfen (Knack

R),

imidacloprid (ProvadoR) and spinosad (Spin-

TorR). Populations of the silverleaf whitefly

(Bemisia tabaci [Gennadius], Biotype B) were

high and tomato yellow leaf curl virus infection

rate of susceptible tomatoes in nearby plots

planted with a susceptible tomato, ‘FL 47’ was

high. No ‘Tygress’ plants showed any symp-

toms of virus infection. Early blight, Alternaria

solani, appeared before flowering and was suc-

cessfully controlled until the first harvest, but

thereafter the disease became severe.

The tomato fruits were harvested from 24

plants per plot on June 1, June 13 and June 22,

2007. Fruits were graded following Florida

Tomato Committee Standards (Brown, 2000).

The fruits were separated into extra large, large,

medium and small after each harvest and the

marketable and yields and total number of

fruits were recorded.

Immediately after the final harvest, root

samples were taken from 6 tomato plants per

plot and the roots were rated for galling (data

not shown).

The data were subjected to analysis of vari-

ance and Duncan’s multiple range tests by

means of SAS (version 8.1, SAS Inst., Inc.,

Cary, NC, USA). When significant (P < 0.05 or

less) F values were found in the Analysis of

Variance (ANOVA), the means were separated

by Duncan’s Multiple Range Test (DMRT).

Results and Discussion

The levels of infection of the tomato roots

with the root knot nematode, Meloidogyne

incognita, in both experiments were extremely

light and not significantly different in any

treatment than in the control (data not shown).

Also the levels of root rot were uniformly light

in all of the plots (data not shown).

Results of Study no. 1 (Table 1):

Rhizoctonia solani populations in the sa-

chets (Table 1) were not significantly sup-

pressed by any of the fumigant treatments.

Fusarium oxysporum f. sp. Lycopersici

13

populations in the sachets were suppressed to

the greatest extent by treatment no.1 (shank-

applied chloropicrin followed by drip-applied

metam potassium + metalized plastic mulch),

followed by treatment no. 3 (shank applied

50% iodomethane + 50% chloropicrin +

metalized plastic mulch), but these population

levels were not statistically different than the

numerically higher levels following treatment

no.2 (pre-plant incorporated napropamide +

halosulfuron, followed by fosthiazate sprayed

onto the bed surface, then shank applied chlo-

ropicrin + metalized plastic mulch) and treat-

ment no.4 (shank applied MC-33 + metalized

plastic mulch).

Clearly, even chloropicrin (PIC) at 100

pounds/acre (112.1 kg/ha) alone or in combi-

nation with KPAM, and with the herbicides and

the nematicide in the 2nd

treatment is an insuf-

ficient dose to suppress Rhizoctonia solani

even moderately and to suppress F. oxysporum

f. sp. Lycopersici strongly. Also chloropicrin

(PIC) at 75 pounds/acre (84.1 kg/ha) in combi-

nation with an equal weight of iodomethane

and chloropicrin (PIC) at 57.8 pounds/acre

(64.7 kg/ha) in combination with 117.3

lbs/acres (131.4 kg/ha) of methyl bromide is an

insufficient dose to suppress Rhizoctonia solani

even moderately and to suppress F. oxysporum

f. sp. Lycopersici strongly.

The total marketable tomato yields were the

highest in treatment no. 1 (shank-applied chlo-

ropicrin followed by drip-applied metam potas-

sium + metalized plastic mulch) and treatment

no.3 (shank applied 50% iodomethane + 50%

chloropicrin + metalized plastic mulch). Fol-

lowed by treatment no.4 (shank applied MC-33

+ metalized plastic mulch), treatment no.2 (pre-

plant incorporated napropamide + halosulfuron,

followed by fosthiazate sprayed onto the bed

surface, then shank applied chloropicrin +

metalized plastic mulch) and the untreated

control, which had the lowest yield. Only the

chloropicrin + metam potassium and io-

domethane + chloropicrin treatments had sta-

tistically higher total marketable tomato yields

than the untreated control. Tomato yields in the

remaining treatments were not statistically dif-

ferent than in the untreated control, probably

because the field was not severely infested with

nutsedge, root knot nematode, Fusarium or

Rhizoctonia.

The total number of marketable tomato

fruits was the highest in the chloropicrin +

metam potassium treatment and this number

was statistically greater than in the untreated

control. However none of the numbers of fruits

obtained in the chemical soil treatment were

different statistically.

The best overall treatment effects in study

no. 1 trial were obtained with chloropicrin +

metam potassium (PIC + KPAMR) and io-

domethane + chloropicrin (MIDASR).

Results of Study no. 2 (Table 2):

Rhizoctonia solani populations in the sa-

chets were not significantly suppressed by any

of the fumigant treatments. Fusarium

oxysporum f. sp. Lycopersici populations were

significantly, but not drastically, suppressed by

all of the formulations containing chloropicrin.

However, Fusarium populations in the sachets

exposed to pure DMDS at the highest rate were

not significantly lower than in the untreated

control. All of the formulations containing

chloropicrin drastically suppressed Cyperus

esculentus L. populations in the sachets,

but not to a statistically significant greater

extent than by DMDS 100; 56 gal acre-1

[524 l ha-1

] or by DMDS 100; 74 gal acre-1

[692 ha-1

].

Clearly DMDS without chloropicrin had

only a mild effect against yellow nutsedge and

no effect against Fusarium and Rhizoctonia.

However DMDS in combination with chlo-

ropicrin was highly effective against yellow

nutsedge and moderately effective against

Fusarium. Chloropicrin weighs 13.79 lbs/gal at

20 oC, and DMDS weighs 8.85 lbs/gal at 20

oC,

In the DMDS-chloropicrin 79:21 (w/w) mix-

ture, chloropicrin make up 14.05% of the vol-

ume. The weight of chloropicrin applied per

14

acre in each of the three different application

rates of DMDS 79-21 was 76 lbs/acre (85.2

kg/ha), 112 lbs/acre (126 kg/ha) and 148

lbs/acre (166 kg/ha). However even at the

highest rate at which 560 pounds of DMDS is

combined with 148 pounds of chloropicrin

Fusarium was not suppressed to a greater ex-

tent than by MC-33 in which only 57.8

pounds/acre (64.7 kg/ha) is combined with

117.3 lbs/acres (131.4 kg/ha) of methyl bro-

mide. This suggests that Fusarium control

needs to be achieved by the development of

resistant tomato cultivars.

The total marketable tomato yield was the

highest in the DMDS 79-21; 74 gal acre-1

[692 l

ha-1

] treatment, but not significantly higher than

in the DMDS 79-21; 56 gal acre-1

[524 l ha-1

]

treatment. Tomato yields in the remaining

treatments were not statistically different than

in the untreated control, probably because the

field was not severely infested with nutsedge,

root knot nematode, Fusarium or Rhizoctonia.

The total number of marketable tomato

fruits was the highest in the DMDS 79-21; 74

gal acre-1

[692 l ha-1

] treatment but not signifi-

cantly higher than in the DMDS 79-21; 56 gal

acre-1

[524 l ha-1

] and in the DMDS 79-21; 56

gal acre-1

[524 l ha-1

] treatments, nor than in the

MC 67-33; 175 lbs acre-1

[196 kg ha-1

] and

DMDS 100; 38 gal acre-1

[355 l ha-1

] treat-

ments.

The best overall treatment effects in this 2nd

trial occurred with DMDS 79-21; 74 gal acre-1

[692 l ha-1

] followed by DMDS 79-21; 56 gal

acre-1

[524 l ha-1

]

Acknowledgements

The MC-33 was provided by Helena

Chemical Co., Florida City, FL. MIDAS was

donated by Arysta Life Science Corporation,

and fosthiazate was provided courtesy of Dr.

James P. Gilreath, GCREC, Wimauma. We are

deeply grateful to Tony Estes, Cerexagri-Nisso,

LLC for providing the DMDS formulations,

and to Mr. Phil Crumpacker, Hendrix and Dail,

Inc. for assistance in applying the fumigants.

Mr. Robert Stubblefield, Mr. Jose Castillo and

other members of the Center’s field crew pro-

vided invaluable expert assistance. This work

was financially supported in part by the Florida

Tomato Committee.

15

Table 1. Effects of methyl bromide plus chloropicrin and of four alternative soil sterilization treatments of raised beds in suppressing

Cyperus esculentus L, Fusarium oxysporum f. sp. lycopersici, and Rhizoctonia solani, and on total marketable tomato yield

and numbers of marketable tomato fruits.

Treatment Rhizoctonia

solani

Percent

recovery of

colonies

Fusarium

oxysporum f. sp.

Lycopersici

Percent recovery

of colonies

Cyperus esculentus L

Mean number of tu-

bers out of 20 per sa-

chet that germinated

Total market-

able tomato

yield,

grams/plot

Total number

of marketable

tomato fruits

per plot

(1) Shank-applied chlo-

ropicrin followed by drip-

applied metam potassium +

metalized plastic mulch

16.7 a 18.3 b 0.0 b 41304 a 488 a

(2) Preplant incorporated

napropamide + halosulfu-

ron, followed by fosthi-

azate sprayed onto bed sur-

face, then shank applied

chloropicrin + metalized

plastic mulch

6.6 a 63.3 ab 0.0 b 34656 ab 427.3 ab

(3) Shank applied Io-

domethane (MIDAS) +

metalized plastic mulch

21.7 a 46.7 b 0.0 b 39688 a 452.5 ab

(4) Shank applied MC-33 +

metalized plastic mulch

16.7 a 66.7 ab 0.0 b 37932 ab 433.7 ab

(5) Untreated control

(metalized plastic mulch

only)

20.0 a 100.0 a 13.3 a 32234 b 391.7 b

Means within a column followed by the same letter(s) do not differ significantly (P > 0.05; DMRT).

16

Table 2. Effects of fumigation of raised beds with DMDS alone, DMDS plus chloropicrin and methyl bromide plus chloropicrin in

suppressing Cyperus esculentus L, Fusarium oxysporum f. sp. lycopersici, Rhizoctonia solani, Meloidogyne incognita, and on

total marketable tomato yield and numbers of marketable tomato fruits.

Treatment Rhizoctonia

solani

Percent

recovery of

colonies

Fusarium

oxysporum f.

sp. lycopersiciy

Percent

recovery of

colonies

Yellow nutsedge,

Cyperus esculentus Lz

Mean number of tubers

out of 20 per sachet that

germinated

Total mar-

ketable to-

mato yield,

grams/plotz

Total num-

ber of mar-

ketable to-

mato fruits

per plotz

Non-treated control 42.5 a 100.0 a 16.5 a 26459 bc 292.0 bc

DMDS 100; 38 gal acre-1

[355 l ha-1

] 22.5 a 92.5 ab 3.8 b 25548 bc 315.8 abc

DMDS 100; 56 gal acre-1

[524 l ha-1

] 57.5 a 100.0 a 2.5 bc 21156 c 268.3 c

DMDS 100; 74 gal acre-1

[692 ha-1

] 20.0 a 100.0 a 1.8 bc 25083 bc 276.5 c

DMDS 79-21; 38 gal acre-1

[355 l ha-1

] 40.0 a 62.5 ab 0.3 c 26620 bc 320.5 abc

DMDS 79-21; 56 gal acre-1

[524 l ha-1

] 22.5 a 50.0 ab 0.0 c 32186 ab 369.8 ab

DMDS 79-21; 74 gal acre-1

[692 l ha-1

] 15.0 a 47.5 ab 0.0 c 34848 a 381.8 a

MC 67-33; 175 lbs acre-1

[196 kg ha-1

] 62.5 a 35.0 b 0.0 c 26994 bc 318.8 abczMeans within a column followed by the same letter(s) do not differ significantly (P > 0.01; DMRT).

yMeans within this column followed by the same letter(s) do not differ significantly (P > 0.05; DMRT).

17

Breeding Tomatoes for Florida

J. W. Scott

Gulf Coast Research & Education Center

University of Florida, IFAS

14625 CR 672

Wimauma, FL 33598

W. Klassen

Tropical Research & Education Center

University of Florida, IFAS

18905 SW 280th Street

Homestead, FL 33031

Abstract

High lycopene, Fusarium wilt resistant

hybrid ‘Fla. 8153’ was released in October

2006. This hybrid has performed consis-

tently well in taste panels over several years

and if harvested vine-ripe and branded could

compete well with greenhouse tomatoes in

supermarkets. Seed production is underway

and good volumes of seed should be available

in fall 2007 for the 2008 season. Fusarium

crown and root rot resistant hybrid Fla.

8413 has performed well on grower trials in

SW Florida over the past two years and has

also done well in GCREC trials. It is pres-

ently being considered for release pending

further testing. Fruit have a consistently

good marketable shape and firmness with

overall good fruit quality and a strong vine.

Tomato spotted wilt resistant hybrid Fla.

8367 yielded very well in the fall 2006 trial

at GCREC and is being considered for re-

lease. Spring data from NFREC is not yet

available. Seven of 9 stage 2 TYLCV resis-

tant hybrids were selected for further testing

while 10 new hybrids were selected for stage

2 testing in the fall. The spring TYLCV in-

oculated yield trial was grown under poor

conditions but some hybrids were selected

for further stage 2 testing.

Introduction

Improved varieties are needed to keep

the Florida tomato industry competitive in a

changing world. Improvements include the

areas of yield, pest resistance, and fruit

quality. Florida’s geography offers many

challenges for tomato improvement, since

high temperatures limit fruit set and are con-

ducive to disease and insect problems. There

are no neighboring states with similar lati-

tudes to most of Florida, so there is less help

in solving agricultural problems than is the

case in many states. Although private com-

panies have tomato breeding programs that

develop varieties for Florida, these compa-

nies are not set up to handle many of the

long-term, high risk projects that could

prove valuable in the future. The University

of Florida tomato breeding program aims at

such projects and works in partnership with

the private companies to deliver improved

varieties of benefit to the Florida tomato in-

dustry.

Much of the groundwork for the devel-

opment of heat-tolerant varieties was done

at the University of Florida (Scott et al.,

1986). ‘Solar Set’ was an important com-

mercial, heat-tolerant variety for 11 years

after it was released (Scott et al., 1989). The

improved heat-tolerance in ‘Solar Fire’, re-

leased in 2003, could be of benefit to grow-

ers in seasons with fewer hurricanes than in

2004 when it was being introduced. We now

have Fusarium wilt race 3 resistant varieties

using a resistance gene discovered in a wild

species by this program in the 1980's (Scott

and Jones, 1989; Scott and Jones, 1995).

Breeding lines with Fusarium crown and root

18

rot resistance were released in 1999 (Scott

and Jones, 2000) and UF breeding lines are

in commercial varieties ‘Sebring’, ‘Soraya’,

and ‘Crown Jewel.’ With the impending loss

of methyl bromide, these pathogens could

become more widespread. Other diseases

such as bacterial wilt and spotted wilt occur

in Florida, but cause far more damage in

other regions of the world. If these diseases

become more prevalent here, resistant varie-

ties will prove beneficial. Tomato yellow

leaf curl virus (TYLCV) is a serious threat to

Florida tomato production (Polston et al.,

1999) and some crops have sustained severe

losses in the last few years. Commercial

companies have released TYLCV resistant

varieties but none have yet been adapted by

Florida growers. Our project has been ongo-

ing since 1990 utilizing different resistance

genes derived from the wild species Ly-

copersicon chilense. It appears that four

genes have been introgressed, with two genes

needed in a variety to provide resistance.

These genes must be incorporated into both

parents of a hybrid since the resistance is

not dominant. This makes the breeding of

finished varieties more difficult but such hy-

brids are presently being evaluated and this

is discussed herein. Molecular markers

linked to the resistance genes are being de-

veloped that will accelerate future breeding

progress and these will be provided to all

tomato breeders for their use and benefit to

the Florida industry.

Tomatoes have met with dissatisfac-

tion in the marketplace. Essentially, this re-

lates to compromises that are made in pro-

viding fruit that will ship well. Solutions to

this problem are not simple. Research is

needed to provide tomatoes that will be

more acceptable to consumers. On the bright

side, Nugyen and Swartz, (1999) and others

have shown that lycopene, the red pigment

in tomato, has strong antioxidant properties

that reduce several cancers. Work in the

breeding program has been ongoing for 25

years with a crimson gene (ogc) that im-

proves internal tomato color and increases

lycopene content. Seven breeding lines with

this gene have been released to seed compa-

nies over the last 12 years. Crimson varieties

may be a boon to the Florida industry in the

near future. Genetic alteration of plant archi-

tecture might provide ground tomatoes that

reduce labor costs for staking and harvesting.

This could also be important for future pro-

duction in Florida. This is another long-term,

high risk project that is being pursued in our

program that is not likely to be attempted

by the private sector. Florida Tomato Com-

mittee funding has been imperative to the

operation of this breeding program, an in-

vestment that has and will continue to pay

dividends.

Objectives of this project were

1. To develop varieties or breeding lines

resistant to soil-borne pathogens.

2. To develop improved heat-tolerant

inbreds and hybrids.

3. To develop commercially acceptable

breeding lines and hybrids resistant

to TYLCV or tomato spotted wilt vi-

rus.

4. To improve fruit quality and post-

harvest characteristics.

5. To develop commercial hybrids for

the Florida tomato industry.

Objective 1

Methods. There were 68 lines

screened for Fusarium wilt race 3 and 113

19

lines screened for Fusarium crown rot in fall

2006 and spring 2007. There were 46 lines

inoculated with the bacterial wilt pathogen in

fall 2006. In spring 2006 32 lines were

screened for bacterial wilt resistance but the

inoculation failed. A replicated yield trial

comparing advanced inbreds was conducted

in fall 2006 and spring 2007 that included 1

line resistant to Fusarium wilt race 3 and 3

lines resistant to Fusarium crown rot. At

NFREC 3 Fusarium wilt race 3 resistant and

3 Fusarium crown rot resistant hybrids were

tested in fall 2006.

Results. Several hybrids with huge-

fruited Fla. 8293 as a parent looked good in

fall 2005 and spring 2006 trials. Fla. 8293

was supposed to be Fusarium crown rot re-

sistant but recent selections of it were sus-

ceptible. We have gone back to an earlier se-

lection and will soon know if this selection

carries resistance. Fla. 8293 is a parent in

hybrid Fla. 8413 that has looked good in

grower and GCREC trials. Several other

Fusarium crown rot resistant hybrids (Fla.

8412, Fla. 8415) have shown merit and are

being tested further for possible release.

Vines of these crown rot lines have looked

strong under some difficult growing condi-

tions. New crown rot resistant inbreds Fla.

8491, Fla. 8499, and Fla. 8497 have all

looked good in last year’s trials and are pres-

ently being tested in new hybrid combina-

tions. Fla. 8109 has a high level of bacterial

wilt resistance with large fruit and it has

been used in a number of crosses with elite

inbreds to improve horticultural type. Sev-

eral inbreds have been developed from these

crosses and many have huge fruit, some with

parental potential. Furthermore, some ap-

pear to have bacterial spot tolerance so this

will be watched carefully as new hybrids are

evaluated for commercial potential.

Objective 2

Methods. Heat-tolerant (HT) fruit

setting ability is being incorporated into all

phases of the breeding program. For instance

many lines being developed with bacterial

spot tolerance have heat tolerance as well. In

winter 2007 27 HT lines were evaluated at

TREC and in fall 2006 and spring 2002, 184

HT inbreds were evaluated at GCREC for

their performance. There were 9 HT hybrids

and 14 HT inbreds tested in fall 2006 and

spring 2007 yield trials. At NFREC in fall

2006, 4 HT hybrids were evaluated in ob-

servation trials.

Results. Inbred Fla. 8044 has been

mentioned as a line with outstanding HT in

past reports. It is a parent in tomato spotted

wilt resistant hybrids Fla. 8367 and Fla.

8485B mentioned in this report. It was also

crossed with Fla. 8109 (see objective 1) and

Fla. 8493 was developed. Fla. 8493 had the

highest marketable yield in both fall 2006

and spring 2007 GCREC yield trials and it is

being tested as a parent line at present. Fla.

8485B is a crimson, HT hybrid that did well

in yield trials during the last year. As indi-

cated the HT trait is now in several lines

listed under other projects so is more ubiqui-

tous than indicated here. Heat-tolerant hy-

brids with the proper horticultural charac-

teristics should provide Florida growers with

varieties that set marketable fruit more relia-

bly under stress conditions such as either

cool or high temperatures.

Objective 3

Methods. Geminivirus resistance.

20

There were 218 and 270 lines inoculated

separately with ToMoV and TYLCV, rated

for disease severity, and evaluated for horti-

cultural type in fall 2006 spring 2007, re-

spectively. There were 86 resistant hybrids

evaluated during the year in stage 1 testing.

Crosses were made to produce 91 hybrids,

some new and some to replenish seed. Nine

hybrids were in stage 2 testing in the fall and

7 of these were retested in the spring along

with 9 others that were advanced from stage

1 testing in the fall. Twelve inbreds were

tested in advanced trials during the year.

Spotted wilt resistance. There were 17 lines

with spotted wilt resistance evaluated in fall

2005 and spring 2006. Three hybrids were

evaluated in yield trials at GCREC and 5

were evaluated at NFREC. There were 22

F2’s with a new resistance source evaluated

in fall 2006. In the spring at NFREC 108 F3

lines with this new resistance were evalu-

ated. This new source has resistance to a

Hawaiian strain of the virus that overcomes

Sw-5 the resistance gene that is used in all

present commercial hybrids.

Selection for conventional (not the

new) resistance is done with sequence char-

acterized amplified region (SCAR) molecular

markers that eliminate the need to screen

with thrips and potentially spread the virus

in the west coast growing region.

Results. Geminivirus resistance.

The goal is to develop commercial quality

hybrids with resistance in both parents since

resistance in one parent has not been ade-

quate. Seven of 9 hybrids tested in fall 2006

were tested again in spring 2007. However,

irrigation problems in the spring prevented a

good assessment of hybrids in the trial. Sev-

eral hybrids will continue to be tested while

some others were too small fruited. In spring

2007, 149 selections were made and 5 F1's

were advanced to F2. In spring some new

inbreds with good characteristics were se-

lected and will next be tested as parents.

Molecular marker work is progressing and

markers are beginning to accelerate breeding

efforts for resistance to TYLCV although

more markers need to be elucidated. An im-

portant gene Ty-3 was described (Ji et al.,

2007) and a closely linked molecular marker

has been discovered. This will be licensed to

the tomato breeding community in the near

future. Ultimately we want to combine

TYLCV resistance with heat-tolerance, bac-

terial spot resistance and other desirable

traits in the same variety.

Spotted wilt resistance. Zeraim Ged-

era has seed available for grower testing of

released hybrid Fla. 7964. Fla. 8124C, a re-

sistant parent that is presently being tested

in several hybrid combinations, did well in

both spring and fall trials. Two hybrids with

the most promise for release are Fla. 8363

and Fla. 8367. These will be tested further,

especially at NFREC where these and other

hybrids are being tested this fall. Fla. 8367

did very well in the fall GCREC trial but it

could not be tested in the spring because of

seed lot germination problems.

Objective 4

Methods. Fruit quality and shelf life

are emphasized in all breeding projects. One

method to improve shelf-life is to develop

varieties with ultrafirm (UF) fruit. In the fall

and spring 18 UF inbreds were evaluated.

Another aspect of fruit quality is the devel-

opment of high lycopene varieties by using

the crimson (ogc) gene. This gene is widely

distributed in the various breeding projects.

21

New hybrids are continually being made and

evaluated.

There were 44 and 37 lines evaluated

primarily for improved flavor in the fall and

spring, respectively. Nineteen of these lines

were also evaluated at TREC. Part of this

work involves the incorporation of high sug-

ars from a cherry line into large-fruited lines.

The most interesting lines from all flavor

work are tested in flavor trials described in

the grant report on flavor with cooperator

Dr. Elizabeth Baldwin.

Another project is to develop toma-

toes that do not require staking by use of the

brachytic (br) gene that reduces plant height

and increases side shoots. These tomatoes

are called compact growth habit (CGH) to-

matoes. In winter 2007 92 CGH lines were

evaluated at TREC and in fall and spring 158

lines and 43 hybrids were evaluated at

GCREC. Jointless tomatoes are also receiv-

ing considerable attention with 46 and 58

lines evaluated at GCREC and TREC, re-

spectively. In the fall 65 jointless hybrids

were evaluated at GCREC. During the year

39 new jointless hybrids were made and 41

new CGH crosses were made with most be-

ing jointless.

Finally, a project has been underway

for a number of years to develop a superior

tomato cultivar or hybrid especially well-

suited for Miami-Dade County winter

growing conditions. This thrust began in

1999 when Dr. Jim Strobel selected a series

of ‘Sanibel’ plants from a planting at the

Knaus Berry Farm, Homestead. These

‘Sanibel’ lines were advanced through several

cycles of selection at Homestead,

Fletcher, NC and at Bracey, VA. The late

Dr. Leandro Ramos crossed some of these

lines to some large-fruited, crimson, jointed

pedicel lines provided by Dr. Randy

Gardner, NCSU. Subsequently some of

these lines have been crossed to multiple

disease-resistant, firm, large-fruited, crimson

lines from the breeding program at GCREC.

Our efforts have focused on selection

of vigorous determinate plants (equal to or

larger than ‘Sanibel’ in vine status), jointless,

large globe-shaped fruit with glossy red ex-

ternal color, very little yellow shoulder and

cracking, and tolerant to graywall. The inter-

nal structure of the fruit should be fleshy,

firm, uniformly crimson in color, with a stem

core extension of white tissue of _ inch or

less, and with superior flavor. Firmness and

shelf life characteristics should be such that

the breakers and pink fruit can withstand the

picking, packing and transportation proc-

esses; and arrive at the market in prime con-

dition with deep red internal and external

color–and have good flavor.

Results. Fla. 8153 was released in

October 2006 and will likely be sold under

the trademark Flora-Lee. Some quality data

from this hybrid has been described in the

reports with Liz Baldwin. This variety is a

premium tomato for the supermarket trade

and is meant to be harvested at the breaker

stage. The concept is to better compete with

greenhouse grown tomatoes. Fla. 8297 is a

crimson UF line with very good flavor that

looked good in several hybrid combinations

including the crimson HT F1 Fla. 8485. Fla.

8107, a CGH hybrid, was tested as a proto-

type for stake-less tomato production on

grower farms in Dade county. The plant

type was good and yields were generally

good. There was some off-shape fruit that

require improvement. The trial at TREC was

not ideal due to irrigation problems and a

22

severe infestation of early blight. Neverthe-

less, some lines did well and hopefully ge-

netic progress was made in selecting them.

Numerous selections with jointless stems

were made that would allow for mechanical

harvest.

Twenty-three of the best self-

pollinated lines and F1 hybrids of the im-

proved lines with ‘Sanibel’ lineage crossed to

the multiple disease-resistant, firm, large-

fruited, crimson lines developed in the

GREC and North Carolina programs were

evaluated in 2006-2007 in one grower’s field

near TREC and 6 lines were evaluated in a

second grower’s field 15-miles north of

TREC. Four of these lines appeared to be

especially promising. Subsequent selections

from these same lines and hybrids of these

lines with advanced jointless lines from

GCREC were evaluated at GCREC in the

spring and yielded very well. Testing will

continue in the 2007-2008 season.

Objective 5

Methods. Hybrids anticipated to

have commercial potential are evaluated for

horticultural type in replicated breeding

plots each season (stage 1). After the initial

evaluation, those selected for further (stage

2) testing are put in observation trials at

GCREC and NFREC, with some also being

tested at TREC. Those that perform well in

the observation trials are tested in state rep-

licated trials (at the above 3 centers and

IRREC) and in trials on grower farms (stage

3). For seed production, it is hoped that the

initial crossing produces enough seed for the

first two evaluations. When a hybrid moves

onto the advanced trial phase more seed is

produced at GCREC or sometimes by seed

companies.

Results. Seed was increased for 78

hybrids that are in stage 2 testing. In addi-

tion, 15 crosses were made for stage 1 hy-

brid testing for bacterial spot tolerance.

TYLCV tolerant, CGH, and jointless crosses

are mentioned elsewhere. Extra seed was

made for Fla. 8367 and Fla. 8413 that will be

moving to stage 3 testing.

Literature Cited:

Ji, Yuanfu, David J. Schuster, and Jay W.

Scott. 2007. Ty-3, a begomovirus resistance

locus near the Tomato yellow leaf curl virus

resistance locus Ty-1 on chromosome 6 of

tomato. Molecular Breeding (in press, avail-

able on line)

Nguyen, M.L. and S.J. Schwartz. 1999. Ly-

copene: Chemical and biological properties,

Food Technol. 53(2): 38-45.

Polston, J.E., R.J. McGovern, L.G. Brown.

1999. Introduction of Tomato yellow leaf

curl virus in Florida and implications for the

spread of this and other geminiviruses of

tomato. Plant Dis. 8384-988.

Scott, J. W., and J. P. Jones. 1989. Mono-

genic resistance in tomato to Fusarium ox-

ysporum f. sp. lycopersici race 3. Euphytica

40:49-53.

Scott, J. W., and John Paul Jones. 1995. Fla.

7547 and Fla. 7481 tomato breeding lines

resistant to Fusarium oxysporum f. sp.

lycopersici races 1, 2, and 3. HortScience

30(3):645-646.

23

Scott, J. W., and John Paul Jones. 2000. Fla.

7775 and Fla. 7781: Tomato breeding lines

resistant to Fusarium crown and root rot.

HortScience 35(6):1183-1184.

Scott, J. W., S. M. Olson, J. J. Bryan, T. K.

Howe, P. J. Stoffella, and J. A. Bartz. 1989.

Solar Set: A heat tolerant, fresh market to-

mato hybrid. Fla. Agric. Expt. Sta.

Circ. S-359 10p.

Scott, J. W., R. B. Volin, H. H. Bryan, and

S. M. Olson. 1986. Use of hybrids to de-

velop heat tolerant tomato cultivars. Proc.

Fla. State Hort. Soc. 99:311-314.

24

Breeding Tomatoes for Resistance to

All Races of the Bacterial Spot

Pathogen

J. W. Scott

Gulf Coast Research & Education Center

University of Florida

14625 CR 672

Wimauma, FL 33598

J. B. Jones

Plant Pathology Department

University of Florida

Gainesville, FL 23611

Abstract

There are 4 races of the bacterial spot

pathogen that infect tomato, but races T3 and

T4 are of primary concern in Florida. Race T3

is widespread, whereas the prevalence of T4 is

not known, although it has been identified

several times in South and West Florida. Par-

ent lines with T3 resistance have been devel-

oped and crosses made with horticulturally

advanced, susceptible parents to obtain hy-

brids that have commercial potential with in-

termediate resistance. The best of these, Fla.

8314, has had outstanding yields but fruit size

is slightly less than that of ‘Florida 47’. This

hybrid yielded well in trials last year but is not

being released because of the fruit size being

slightly small and due to the presence of race

T4 in Florida. No hybrids with T3 and T4

resistance are acceptable for release at least

one new hybrid looked very good in the spring

and it will be tested further. Several inbred

lines have looked good and crosses will be

made with these in attempt to find hybrids

acceptable for release. Genetic studies have

not been definitive as yet but indicate epistasis

is present. Three sources of resistance are be-

ing studied and combining resistance from

these sources may provide increased resistance

levels. Molecular marker work is underway to

identify and combine resistance genes to de-

termine if such combinations improve resis-

tance and ultimately to be able to breed for

resistance using marker assisted selection

which will accelerate the breeding process.

Introduction

Bacterial spot is still the most ubiquitous

disease problem of tomatoes in Florida. Four

tomato races have been discovered to date and

these belong to four species of Xanthomonas

(Xcv), the bacterial spot pathogen (Jones et

al., 2005). In Florida, there have been three

races; the original race (T1), the race discov-

ered in 1991 (T3) (Jones et al., 1995), and a

new race (T4) (Astua-Monge et al., 2000).

Race T3 has largely replaced race T1 in Florida

(Jones et al., 1998). Race T4 has mutated from

T3 and appears to be spreading. It has been

found in at least Dade, Manatee, and Hillsbor-

ough counties. It is not known how important

this race is now or might become should race

T3 tolerant varieties be commercially grown.

Race T2 was originally reported from Brazil,

but has now been isolated in some states in the

USA including Ohio but not Florida.

Our breeding project began in 1983 when

we found Hawaii 7998 was resistant to race T1

(Jones and Scott, 1986). In the early 1990’s

resistance to race T3 was discovered in several

accessions including Hawaii 7981 (Scott et al.,

1995), and this resistance has been incorporated

into advanced T1 resistant breeding lines. Lines

with resistance to T1 and T3 also had tolerance

to race T2, whereas lines with resistance to

either race alone were susceptible to T2 (Scott

25

et al., 2003). This suggests combining bacterial

resistance genes in a line may have unexpected

beneficial effects against other bacterial races.

We found PI 114490 was resistant to race T2 in

the summers of 1995 and 1996 and this was

further verified from 1997 through 2005 at

Wooster, Ohio. PI 114490 also was resistant to

race T1 and tolerant to race T3 (Scott et al.,

2003). In studies from 2003 and beyond we

found PI 114490 was resistant to race T4

(Scott et al., 2006; Yang et al., 2005). The gen-

eral resistance from PI 114490 needs to be

incorporated into advanced breeding lines. This

general resistance could be important, should

race T2 migrate into Florida, or it might also

protect against any new race which might

emerge in the future. We also found resistance

to races T3 and T4 in Fla. 8326 a breeding line

derived from PI 126932 (Scott et al., 2006). PI

128216 is also resistant to races T3 (Scott et

al., 1995) and race T4 (Scott et al., 2006). It is

desirable to develop genetic information on

these resistances to allow for more efficient to

breed for race T4 resistance and combine this

with T3 resistance. Varieties with T3 and T4

resistance would provide Florida tomato grow-

ers with protection from losses due to bacterial

spot infection and allow for minimal spraying

thus saving money and reducing environmental

concerns.

The objectives of this research were

1) To develop commercial hybrids

with tolerance to bacterial spot race

T3 and T4.

2) To develop inbreds with durable

resistance for use as parents in

commercial hybrids.

3) To determine genetic information

about raceT3 and T4 resistance.

Objective 1

Methods. During the fall and spring there

were 48 large-fruited hybrids in stage 1 testing

and 33 in stage 2 testing at GCREC. Eleven

hybrids were tested at NFREC in fall 2006 and

8 hybrids were tested in Fletcher, NC in sum-

mer 2006. There were 35 cherry F1’s and 6

plum F1’s tested in stage 1 at GCREC. There

were 65 crosses involving bacterial spot resis-

tant parent lines.

Results. Fla. 8314 has tolerance to T3 and

marketable yields have been very reliable over

several years of testing including 3 trials in the

last year. However, the fruit size is a little less

than that of ‘Florida 47’ and other commer-

cially grown varieties. Despite the reliable

marketable yields and good fruit firmness, it

was not felt that growers would adapt Fla.

8314 due to a lower percentage of 5 x 6 fruit.

The other issue is the presence of race T4 in the

state. For instance, Fla. 8314 had a lot of bacte-

rial infection in the spring 2007 trial at GCREC

due to T4 infection. Thus, although this hybrid

will continue to be tested it will not likely be

released. There are no prime candidates for

release with T3 and T4 tolerance at present.

Although several hybrids that have been tested

have had certain merits, none has shown enough

advantage to be released. In spring 2007 a new

stage 2 hybrid (8478 x 8208-no official hybrid

designation yet) did very well with a strong

vine and good marketable yield of extra-large

fruit. It will be tested further.

Objective 2

Methods. There were 128, 160, 12, and

44 breeding lines (F2 and more inbred) with

race T3 or race T3 and T4 resistance evalu-

26

ated in fall 2006, spring 2007, summer 2006

at Fletcher, NC, and winter 2007 (TREC),

respectively. Other lines developed from ge-

netic studies were tested as indicated under

objective 3. At GCREC, lines were inoculated

with race T3 in the fall 2006 and T4 in spring

2007. Race T4 has now been occurring natu-

rally at GCREC for about two years, thus we

have started to artificially inoculate with it.

Fifteen lines have been tested in advanced

yield trials at GCREC during the year.

Results. Breeding lines with more ad-

vanced horticultural characteristics typically

have moderate tolerance levels to race T4.

Emphasis is being placed on lines that show

less foliar disease to not only bacterial spot

but early blight as well. Of the lines tested in

replicated trials (stage 2 testing) Fla. 8401H,

Fla. 8495B, and Fla. 8594 looked good. The

former 2 are derived from the cross of Fla.

8233 with heat-tolerant line Fla. 7949B. A

sister line also looked nice at TREC last win-

ter. Three lines from the genetic studies (see

objective 3) looked impressive in the spring;

one line from the 8233 x 7776 cross and two

lines from the 8233 x 8326 cross. These will

be put into stage 2 testing and crosses will be

made to develop hybrids for objective 1. In-

bred Fla. 8496 appeared outstanding in NC

but hybrids with this line as a parent were

disappointingly small-fruited in spring trials.

Several early generation selections derived

from Fla. 8517 show some promise for plum

tomatoes. A line with T3 resistance only

looked outstanding with huge fruit at TREC

and will be used in crossing for improved hy-

brids.

Objective 3

Methods. We are working with T4 resis-

tant genes in breeding lines derived from 3

sources; PI 114490, PI 126932, and PI

128216. Fla. 8326 has resistance from PI

126932 as well as resistance to other races

from Hawaiian sources. Fla. 8233 has resis-

tance from PI 114490 and Hawaiian sources.

Fla. 8517 has resistance with PI 128216 and

PI 114490 in its background. A family was

previously developed with Fla. 8326 and sus-

ceptible parent Fla. 7946. This family and 5

F3’s were planted and inoculated with race T4

at Citra in summer-fall 2006 as in 2005. Also

36 F3’s between 8233 x 8326 were planted at

Citra. In the fall, families of 8233 and 8517

crossed with susceptible Fla. 7776 were

planted at GCREC along with 29 F4’s derived

from the 8233 x 8326 cross. In spring 2007,

families of 8233 and 8517 each crossed with

susceptible 7776 were grown along with 18

8233 x 8326 F3-F5’s, 7 8326 x 7946 F3’s, 19

8233 x 7776 F3’s, and 19 8517 x 7776 F3’s.

This summer families of 8233 x 7776, 8517 x

7776, and 8326 x 7946 are all planted at Citra

along with 65 F3-F5’s derived from the resis-

tant sources. All plants were inoculated with

race T4 and rated for disease severity. Selec-

tions were made for horticultural traits and

resistance in the F2 and later generations. A

Ph.D. student, supported from other funding,

is conducting this work for his dissertation.

He is also locating molecular markers linked

to the resistance genes that will accelerate the

bacterial spot resistance breeding progress

once identified.

Results. From the summer 2005 and

2006 experiments the F1 between Fla. 8326

and Fla. 7946 was intermediate between the

27

parents but skewed toward susceptibility.

This would indicate that if this resistance

alone was used one would need resistance in

both parents to have useful resistance in the

hybrid. Inheritance results varied between

experiments and there is some indication of

epistatic gene action. Inheritance from 8233

may also have epistasis which precludes es-

timating the number of genes in control and

heritability. There was not enough disease in

the 8517 family in the spring and no data

were obtained. We hope to get a good data set

from all 3 families in Citra 2007 to clarify in-

heritance of resistance from all the sources.

Analysis of data over the last several years

indicates that all 3 sources provide useful re-

sistance, but sometimes the levels are not as

high as desired under high-disease pressure. In

essence, we have various breeding lines with

fair resistance, but we hope to develop lines

with higher resistance levels. Combining lines

from different resistance sources may accom-

plish this. At present we do have some inter-

esting lines derived from 8326 and 8233, but

we have not proven if they have genes from

both sources yet. The molecular work will be

the only way to discern this. If good markers

are discovered they can also be used for

marker assisted selection which will accelerate

the breeding process. Once lines with resis-

tance genes from different sources are verified

we will find out if they do in fact have en-

hanced T4 resistance. They can also be tested

for races T1 and T2 in Ohio to determine if

they have broad spectrum resistance which

would likely mean the resistance is durable

and not likely to break down with the emer-

gence of new pathogen races.

Literature Cited

Astua-Monge, G., G.V. Minsavage, R.E.

Stall, Eduardo C. Vallejos, M.J. Davis, and J.

B. Jones. 2000. Xv4-avrxv4: A new gene -for-

gene interaction identified between Xantho-

monas campestris pv. vesicatoria race T3 and

the wild tomato relative Lycopersicon pennel-

lii. Molecular Plant-Microbe Interactions

13(12):1346-1355.

Jones, J.B., H. Bouzar, G. C. Somodi, R.E.

Stall, K. Pernezny, G. El-Morsy, and J.W.

Scott. 1998. Evidence for the preemptive na-

ture of tomato race 3 of Xanthomonas cam-

pestris pv. vesicatoria. In Florida. Phytopa-

thology. 88:33-38.

Jones, J.B., G.H. Lacey, H. Bouzar, G.V.

Minsavage, R.E. Stall, and N.W. Schaad.

2005. Bacterial spot- Worldwide distribution,

importance and review. Acta Horticulturae

695:27-33.

Jones, J.B. and J.W. Scott. 1986. Hypersensi-

tive response in tomato to Xanthomonas

campestris pv. vesicatoria. Plant Dis. 70:337-

339.

Jones, J.B., R.E. Stall, J.W. Scott, G.C. So-

modi, H. Bouzar, and N.C. Hodge. 1995. A

third tomato race of Xanthomonas campestris

pv. vesicatoria. Plant Dis. 79:395-398.

Scott, J.W., S.F. Hutton, J.B. Jones, D.M.

Francis, and S. A. Miller. 2006. Resistance to

bacterial spot race T4 and breeding for dura-

ble, broad-spectrum resistance to other races.

Rept. Tomato Genet. Coop. 56:33-36.

28

Scott, J.W., J.B. Jones, G.C. Somodi, and

R.E. Stall. 1995. Screening tomato accessions

for resistance to Xanthomonas campestris pv.

vesicatoria, race T3. HortScience 30:579-581.

Scott, J.W., D.M. Francis, S.A. Miller, G.C.

Somodi, and J.B. Jones. 2003. Tomato bacte-

rial spot resistance derived from PI 114490;

inheritance of resistance to race T2 and

relationship across three pathogen races. J.

Amer. Soc. Hort. Sci. 128(5):698-703.

Yang, W., S.A. Miller, J.W. Scott, J.B. Jones,

and D.M. Francis. 2005. Mining tomato ge-

nome sequence databases for molecular mark-

ers: Application to bacterial resistance and

marker assisted selection. Acta Horticulturae

695:241-249.

29

Development of Premium

Tomato Varieties with High

Lycopene and Fruity/Floral

Flavor Characteristics

Elizabeth A. Baldwin, USDA/ARS

Citrus & Subtropical Products Labora-

tory, Winter Haven, FL

J.W. Scott, University of Florida, Gulf

Coast Research & Education Center,

Wimauma, FL

Charlie Sims, Food Science Department,

University of Florida, Gainesville, FL

Abstract

Tomato fruit were grown in repli-

cated plots in Homestead, FL and the

University of Florida Gulf Coast Re-

search and Education Center in Wi-

mauma and harvested in March and June

of 2007, respectively. Fruit were ana-

lyzed by an experienced sensory panel

for overall flavor, sweetness, and acidity

as well as for chemical components in-

cluding color, soluble solids (SS), indi-

vidual sugars, titratable acidity (TA),

organic acids, vitamin C, and aroma

volatiles. In March some crimson hy-

brids, developed for the Homestead area

as possible Sanibel replacements, were

analyzed including 6153 a jointed com-

mercial hybrid from Syngenta, currently

grown on some acreage in Dade County.

There was little difference in flavor for

the March study on Homestead tomatoes

except that Sanibel and the Syngenta hy-

brid (6153) exhibited less acidity com-

pared to some of the crimson hybrids.

Line 9249 and 9251 were higher in SS

and sugars and the 6153 had a high

SS/TA ratio and low TA. In June, a

newly released crimson (high lycopene)

hybrid, ‘Fla 8153’ was harvested at table

ripe stage and rated along with tomatoes

typical of the Florida industry, including

some indeterminate pseudo-heirlooms

(heirloom combined with a parent sel-

ected for superior flavor) and non-

crimson good flavored hybrids or in-

breds developed over the last several

years for flavor. For the June fruit, the

pseudo-heirlooms and Fla. 8485 were

rated highest in flavor and the pseudo-

heirlooms for sweetness. Florida 47 was

rated lowest for flavor and sweetness

and low for acidity along with Fla. 8413

and the pseudo-heirloom Italianx.

The Florida tomato industry would

gain back lost market share with a pre-

mium tomato product that had good fla-

vor. Supermarkets like Publix are al-

ready demanding vine-ripe tomatoes for

their produce departments to enhance

flavor quality. Much of the Florida gas-

green industry currently goes to food

service. Past experienced sensory panels

have shown a preference for tomatoes

with a good sugar/acid balance such as

newly released ‘Fla. 8153’ that has the

added benefit of high levels of lycopene.

In this study, we continued to look at

genotypes with high lycopene back-

grounds, good horticultural characteris-

tics, a good sugar/acid balance, and

sometimes a fruity/floral flavor note that

would differentiate a potential release

from the rest of the fresh tomato market.

We tested some lines under south Flor-

ida conditions, including 6153, a jointed

commercial hybrid from Syngenta, cur-

rently grown on some acreage in Dade

County. We also tested pseudo-

heirlooms, which are heirlooms com-

bined with a parent selected for superior

flavor (Italianx = Fla. 8059 x Cour di

Bue di Albenga; Bulgaianx = Fla. 8214

x unknown Bulgarian land race). High-

lycopene tomatoes like ‘Fla. 8153’ may

garner health benefits due to the anti-

oxidant, anti-cancer activity of this pig-

30

ment as well as having good internal

color and flavor.

Methods

Tomato (Lycopersicon esculen-

tum Mill.) genotypes were grown at

grower plots in Homestead (March,

2005) and in a completely randomized

block design with two blocks and 5

plants per plot at the University of Flor-

ida Gulf Coast Research and Education

Center in Wimauma (June 2007).

Genotypes with superior flavor were

emphasized for comparison with stan-

dard varieties. All varieties were har-

vested at the table ripe stage.

Tomatoes were analyzed by an

experienced panel (30+ panelists) who

sampled tomato wedges representing at

least 4 fruit per cultivar. Sub-samples

were taken 3 times during the panel ses-

sion and prepared for analyses of color

and flavor components by measuring

solids, sugars, acids, color, titratable

acidity, vitamin C, and aroma com-

pounds with refractometer, HPLC,

chromometer, spectrophotometer, titra-

tor, and gas chromatograph (GC). Mean

differences were determined by

Duncan’s Multiple Range at < 0.1 for

sensory and using standard error bars for

chemical analyses.

Results

For March 2007, there was no

difference for overall flavor or sweet-

ness, but Sanibel and the Syngenta hy-

brid (6153) exhibited less acidity com-

pared to some of the crimson hybrids

(Table 1), which was reflected in the low

TA for these two lines (Fig. 1B where

circled lines were included in the sen-

sory panel). Other lines were tested

chemically that were not rated by the

sensory panel. Fla. 8583 is a cherry to-

mato crossed with a high sugar line, Fla.

8344 is a “fruity-floral” plum tomato

(selected for fruit-floral flavor), Fla.

8343 is the non “fruit-floral” iso-line to

Fla. 8343, Fla. 8570 is a small

fruited/high acid tomato, line 9255 was

selected for balanced flavor and Fla.

8572 is a crimson line. All of these lines

were selected by the breeder for high

flavor in the field. Lines F;a. 8583 and

Fla. 8344 were high in total sugars, su-

crose equivalents (indicator of sweet-

ness), individual sugars (glucose and

fructose, data not shown), Brix (SS),

SS/TA, and TA. The commercial hybrid

(6153) also had a high SS/TA ratio, but

low TA (Fig. 1A and B). Lines 832, Fla.

8570 and line 9255 were high in citric

acid, while lines 802, 9249 and Fla. 8572

were high in total ascorbic acid (TAA)

or vitamin C (Data not shown). Lines

802, Fla. 8344 and line 9255 exhibited

low hue, indicating more red color (Fig.

1C). These color ratings are an average

of peel and inner color. Fla. 8572, lines

9254 and 9255, Fla. 8344 and Fla. 8343

showed low chroma (low brightness).

31

Table 1. Experienced panel sensory ratings in March 2007. Ratings on a 1-9 scale where

higher numbers indicate more sweetness and acidity and preferred flavor quality.

Line Flavor Sweet Acidity

802 5.00 a 4.24 a 4.65 a

925 4.88 a 4.24 a 3.94 bc

800 4.82 a 4.10 a 4.82 a

803 4.76 a 4.15 a 4.53 ab

Sanibel 4.71 a 4.15 a 3.62 c

6153 4.21 a 3.74 a 3.32 c

Duncan's Alpha = 0.1

For June 2007, Bulgaianx, Fla. 8485 and

Italianx were rated highest for flavor and

Bulgaianx and Italianx for sweetness

(Table 2). Bulgarianx, Fla. 8485, Fla

8610, and Fla. 8153 were rated highest

for acidity. Italianx, Bulgarianx, Fla.

8485, and Fla. 8344 (not included in

sensory, indicated by rectangle in fig-

ures) exhibited the highest Brix (SS),

and Italianx and Fla. 8344 were high in

glucose, fructose (data not shown), and

total sugars (Fig 2A). This generally re-

flects the sensory results for sweetness.

Italianx and Fla. 8344 were highest for

SS/TA and Fla. 8344 for TA (Fig 2B).

Bulgarianx, Fla. 8485, Fla. 8610 and Fla.

8153 were highest in TA for those lines

included in the sensory panel, which re-

sulted in the high sensory rating for

acidity. Florida 47 was not particularly

low in sugars, but was low in TA and

received a poor overall flavor rating.

Volatile analysis is still underway, but

may shed further light on the low overall

flavor rating for Florida 47 compared to

the other lines. Line 8344 had the high-

est level of citric acid (data not shown),

while Florida 47 and Fla. lines 8059,

8214 and 8413 had the highest levels of

TAA (vitamin C, data not shown). Ital-

ianx, Fla. 8153, Bulgiaranx, and Fla.

8485 exhibited the lowest hue (were

most red, Fig 2C). Italianx, Bulgarianx

and Fla. 8344 showed the highest

chroma (most brightness).

32

Table 2. Experienced panel sensory ratings in June 2007. Ratings on a 1-9 scale where

higher numbers indicate more sweetness and acidity and preferred flavor quality.

Line Flavor Sweet Acidity

Bulgarianx 5.87 a 5.42 a 4.38 a

Fla. 8485 5.40 a 4.24 b 4.58 a

Italianx 5.38 a 5.36 a 3.51 b

Fla. 8610 4.60 b 4.07 b 4.51 a

Fla. 8153 4.49 b 4.36 b 4.11 a

Fla. 8413 4.00 bc 4.38 b 3.31 b

Florida 47 3.80 c 3.73 b 3.56 b

Duncan's Alpha = 0.1

In conclusion, the March tomato lines

compared similarly to Sanibel, not being

different in overall flavor or sweetness,

when grown under south Florida condi-

tions. Therefore, these are possible can-

didates to replace Sanibel in south Flor-

ida. For the June study, Italianx and

Bulgarianx, the pseudo-heirlooms, along

with Fla. 8485, exhibited good flavor

and sweetness, while all the lines tested

except Fla. 8413 were rated higher in

flavor compared to Florida 47. These

results were generally reflected in the

chemical data. The results for the other

lines, not included in the sensory panel,

will be of use to the breeder in making

selections for improved flavor.

33

Fig 1. March tomatoes.

Acids

0

2

4

6

8

1 0

1 2

1 4

1 6

1 8

2 0

Cultivars

%S

S/T

A,

TA

or

pH

S.S./T.A.

Titratable

Acidity x 10pH

B

Sugars

0

1

2

3

4

5

6

7

8

9

Cultivars

Perc

en

tTotal Sugars

Sucrose

Equivalence

Brix

A

Color

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

Ch

rom

am

ete

r valu

es

Chroma

Hue

Lycopene x

10

C

34

Fig. 2. June tomatoes.

Sugars

0 . 0

1 . 0

2 . 0

3 . 0

4 . 0

5 . 0

6 . 0

7 . 0

Cultivars

Perc

en

t

Total Sugars

Sucrose

EquivalenceBrix

A

Acids

0 . 0 0

1 . 0 0

2 . 0 0

3 . 0 0

4 . 0 0

5 . 0 0

6 . 0 0

7 . 0 0

Cultivars

% S

S/T

A,

TA

or

pH

S.S./T.A.

Titratable

Acidity x 10

pH

B

Color

0

1 0

2 0

3 0

4 0

5 0

6 0

Ch

rom

am

ete

r valu

es

Chroma

Hue

C

35

Integrated Management of

Whiteflies and TYLCV on Tomato

David Schuster (Entomology) &

Natalia Peres (Plant Pathology)

University of Florida, IFAS, GCREC,

14625 CR 672, Wimauma, FL 33598

Abstract

Experiments were conducted in the

fall 2006 and spring 2007 seasons at the

Gulf Coast Research and Education Center-

Balm to evaluate the singular and integrated

efficacies of Actigard™ and UV-reflective

aluminum mulch for managing the silverleaf

whitefly, Bemisia argentifolii Bellows &

Perring, and tomato yellow leaf curl virus

(TYLCV) on tomato. Treatments consisted

of plants growing on UV-reflective full-

metallized aluminum mulch or white virtu-

ally impermeable mulch with the tomato

plants either treated or not treated with Acti-

gard 50WG. Transplants for the Actigard

treatments were sprayed one week before

transplanting. After transplanting additional

foliar applications of Actigard were made

every two weeks in 2006 and weekly in

2007. Although some significant differences

among the treatments were observed in both

years for the numbers of whitefly adults and

immature life stages, neither the aluminum

mulch nor the Actigard treatments consis-

tently reduced or increased whitefly num-

bers. In 2006 when the whitefly population

was higher earlier in the crop, the plants

growing on the aluminum mulch tended to

have a lower percentage of plants with

symptoms of TYLCV than plants growing

on the white mulch. In addition, foliar appli-

cations of Actigard resulted in further re-

duction of the percentage of symptomatic

plants. In 2007 when the whitefly population

initially was low but increased to a higher

level later in the crop, the aluminum mulch

did not result in reduced incidence of

symptomatic plants but the combination of

aluminum mulch and Actigard did. The

early yield of extra large fruit was higher for

plants growing on the aluminum mulch

compared to plants growing on the white

mulch, although the difference was signifi-

cant only in 2006. Applications of Actigard

reduced the early yield of extra large fruit of

plants growing on the aluminum mulch in

2006 and of plants growing on the white

mulch in 2007. The results suggest that the

use of aluminum plastic mulch can result in

reduced incidence of TYLCV if viruliferous

whiteflies are present early in the crop be-

fore the plastic is covered by the plants. The

results further suggest that pre and post-

plant foliar applications of Actigard may

enhance this effect, but may reduce early

yield of extra large fruit. The rate of the pre-

transplant application of Actigard was dou-

ble the intended rate in these experiments

and could have contributed to the decreased

yields.

Introduction

Whiteflies and tomato yellow leaf curl

virus (TYLCV) are the major economic

pests impacting tomato production in south-

ern Florida during both the spring and fall

growing seasons. TYLCV causes significant

losses on tomatoes in Florida. The host

range of TYLCV is diverse, and some hosts

may not show any symptoms but may ac-

tively serve as a virus reservoir. TYLCV is

vectored by biotype B of Bemisia tabaci

(Genn.), also known as the silverleaf

whitefly B. argentifolii Bellows & Perring.

The host range of TYLCV and its vector

make epidemics extremely challenging to

manage in tomato production fields.

Controlling adult whiteflies with insecti-

cides is effective in preventing disease

transmission, but recently insecticides ap-

plied for control of whitefly adults have

been ineffective. In addition, whitefly bio-

type Q was recently detected in central FL.

36

Even though the biotype has not yet been

detected in tomato production fields, its es-

tablishment would further complicate con-

trol because the biotype is resistant to many

insecticides used to manage biotype B.

These include the nicotinoids (Admire Pro,

Platinum and Assail) as well as the insect

growth regulators (Courier, Knack).

Recently, an integrated management

program has been developed for managing

thrips and the Tomato spotted wilt virus

(TSWV) they transmit. Momol et al. (2004)

have shown during three years of research

that using UV-reflective plastic mulch re-

duces thrips populations and subsequent vi-

rus incidence about one half to two thirds.

The same results were obtained in a com-

mercial tomato field during 2000, 2001, and

2002. In 2005, an experiment was conducted

in southern Italy where biotype Q is present

(Momol et al., unpublished data). Acti-

gard™ (acibenzolar-S-methyl, Syngenta

Crop Protection, Greensboro, NC), a com-

pound inducing the systemic acquired resis-

tance (SAR) response, coupled with UV-

reflective mulches significantly reduced

TYLCV incidences in greenhouse tomatoes.

The SAR natural protection of plants

against pathogens is partly based on a vari-

ety of barriers already present in the plant

before the actual invasion. Plants can acti-

vate protective mechanisms upon detection

of invading pathogens. It is a concept similar

to immunization in warm blooded animals.

The SAR is expressed locally at the site of

primary inoculation and also systemically in

tissues remote from the initial treatment.

SAR has now been demonstrated in many

pathosystems. SAR is active against a broad

range of pathogens, including fungi, bacte-

ria, and viruses. Actigard is an inducer of

SAR against wheat powdery mildew and is

effective against certain diseases of rice and

tobacco. In Florida Louws et al. (2001)

found that Actigard showed activity against

bacterial spot of tomato and Momol et al.

(2004) found disease reduction in the

TSWV-tomato pathosystem. SAR inducers

in tomato show significant promise for the

future of disease management programs.

No single management tactic is effective

in reducing losses from whiteflies and

TYLCV. The objective of this study was to

determine the singular and integrated effica-

cies of Actigard and UV-reflective mulch

for managing whiteflies and TYLCV on to-

mato.

Materials and Methods

Experiments were conducted in the fall

2006 and spring 2007 seasons at the

GCREC-Balm. On Aug 15 and March 20

transplants of tomato cv. ‘FL 47’ were set

18 inches apart on raised beds of Myakka

fine sand soil covered with either white vir-

tually impermeable mulch (Vapor Shield™,

Canslit, Inc., Montreal, Quebec, Canada) or

UV-reflective full-metallized aluminum

mulch (Canslit, Inc., Montreal, Quebec,

Canada). Plots were three, 30 ft long rows

with rows separated by 30 ft of bare soil end

to end. Row spacing was 5 ft side. Plots

were irrigated by a drip irrigation system.

Treatments were replicated four times in a

randomized complete block design and con-

sisted of plants growing on UV-reflective or

white mulch treated or not treated with Ac-

tigard 50WG. Transplants for the Actigard

treatments were treated one week before

transplanting at a rate of 1 gm product/1000

plants. This rate was double the intended

rate of 2 gm/4000 plants. The applications

were made with a 2.5 gal, hand-held CO2-

powered sprayer fitted with a D-5 disk and

#45 core. The sprayer was operated at 60 psi

and delivered 3qt spray/1000 plants in 2006

and 2.75 pt spray/1000 plants in 2007. Ad-

ditional foliar applications of Actigard were

made in the field with a high clearance, self-

propelled sprayer operated at 200 psi and 3.4

mph. It was fitted with eight Albuz orange

nozzles per row and delivered 60 gpa (4

37

nozzles open) and 90 gpa (6 nozzles open.

In 2006 Actigard was applied at 0.75 oz

product/acre on 1, 15 and 29 September at

60 gpa and on 12 Oct at 90 gpa. In 2007

Actigard was applied at a concentration of

0.75 oz product/60 gal on March 21 and 30,

April 5, 19 and 26 at 60 gpa and on May 4 at

90 gpa.

Whitefly densities were assessed on the

middle 10 plants of the middle row of each

plot. The numbers of adults were counted

weekly by carefully turning the third leaf of

two stems of each plant. The numbers of

eggs, 1st, 2

nd & 3

rd, and 4

th instars were

counted weekly on the terminal leaflet from

the 7th

- 8th

leaf counting from the top of

each plant. All plants in each plot were ex-

amined weekly for plants with definite

symptoms of TYLCV. In 2006, plant tissue

was collected from selected plants with typi-

cal TYLCV symptoms to confirm the pres-

ence of TYLCV using PCR (polymerase

chain reaction). Reactions utilized primers

C473 and PTY1v2406 that amplify an 859

bp DNA product specific to TYLCV.

Results

In 2006, the silverleaf whitefly

population as evidenced by the numbers of

adults observed was low to moderate

throughout the trial (Table 1); however, the

population as evidenced by the numbers of

eggs was moderate early in the trial and low

later in the trial (Table 2). Significant differ-

ences in the numbers of adults were detected

on five of the sampling dates (Table 1). In

general, the application of Actigard in com-

bination with aluminum mulch resulted in

fewer adults than application of Actigard in

combination with white mulch. No signifi-

cant differences in the numbers of eggs were

observed on any sampling date (Table 2).

Differences in the numbers of 1st instars

were observed on three sampling dates, and,

on two of the dates, the application of Acti-

gard in combination with white mulch re-

sulted in more nymphs than with the alumi-

num mulch alone (Table 3). The numbers of

2nd

and 3rd

instars differed significantly on

the last three sampling dates (Table 4). Acti-

gard applications on either mulch did not

affect the numbers of nymphs on plants

compared to the respective mulches without

Actigard. The numbers of 4th

instars were

very low and did not differ significantly on

any sampling date (Table 5). Significant dif-

ferences in the numbers of sessile nymphs

were observed on October 23 and 30, but

Actigard applications on either mulch did

not affect the numbers of nymphs on plants

compared to the respective mulches without

Actigard (Table 6). The numbers of total

nymphs differed significantly only on the

last sampling date, when more nymphs were

observed on plants growing on white mulch

and treated with Actigard than on plants

growing on either mulch without Actigard

(Table 7). Applications of Actigard in com-

bination with mulch resulted in lower per-

centages of plants with symptoms of

TYLCV on five sampling dates compared to

the mulches without Actigard (Table 8). In

addition, a lower percentage of plants with

symptoms of TYLCV was observed on alu-

minum mulch compared to plants on white

mulch on all sampling dates except the last.

Visual observations of TYLCV correlated

with PCR with 100% of plants with typical

symptoms.

Yields of cull, small, medium, and

large fruit did not differ among any of the

treatments on either harvest date (Tables 9

and 10) or when combined over both harvest

dates (Table 11). Plants growing on the alu-

minum mulch without Actigard yielded

more extra large fruit than all other treat-

ments on October 31 (Table 9) and when

both harvests were combined (Table 11). No

visible phytotoxicity was observed for any

treatment.

In 2007, the silverleaf whitefly

population as evidenced by the numbers of

38

adults and eggs observed was low early in

the trial but increased to a very high level by

May (Tables 12 & 13). Significant differ-

ences in the numbers of adults were detected

only on May 22 when fewer adults were ob-

served on plants growing on white mulch

combined with Actigard (Table 12). No sig-

nificant differences in the numbers of eggs

were observed on any sampling date (Table

13). Differences in the numbers of 1st instars

were observed only on May 21 when the

application of Actigard in combination with

white mulch resulted in more nymphs than

with the white mulch alone (Table 14). The

numbers of 2nd

and 3rd

instars and sessile

nymphs did not differ significantly on any

sampling date (Tables 15 and 17). On May

14, there were significantly fewer 4th

instars

on plants treated with Actigard and growing

on the white mulch compared to plants not

treated with Actigard growing on the alumi-

num mulch (Table 16). The numbers of total

nymphs differed significantly on 7 May and

June 4, when fewer nymphs were observed

on plants growing on white mulch and

treated with Actigard than on plants growing

on the aluminum mulch without Actigard

(Table 18). On May 16 and June 15, appli-

cations of Actigard in combination with

aluminum mulch resulted in a lower per-

centage of plants with symptoms of TYLCV

compared to the white mulch with Actigard

(Table 19). On May 16, applications of Ac-

tigard on aluminum mulch resulted in a

lower percentage of plants with symptoms

of TYLCV compared to the aluminum

mulch alone. Applications of Actigard in

combination with either mulch resulted in

fewer Liriomyza leafmines compared to the

mulches alone (Table 20).

On June 4, plants growing on white

mulch without Actigard applications yielded

more cull fruit than plants growing on alu-

minum mulch with Actigard applications

(Table 21). Plants growing either on the

aluminum mulch or the white mulch without

Actigard applications yielded more extra

large fruit than plants growing on white

mulch with Actigard applications on 4 June

(Table 21) and when both harvests were

combined (Table 23). Yields of small, me-

dium and large fruit did not differ among

any of the treatments on either harvest date

(Tables 10 and 11) or when combined over

both harvest dates (Table 12). No visible

phytotoxicity was observed for any treat-

ment.

References Cited

Louws, F. J., M. Wilson, H. L. Campbell, D.

A. Cuppels, J. B. Jones, P. B. Shoe-

maker, F. Sahin and S. A. Miller.

2001. Field control of bacterial spot

and bacterial speck of tomato using a

plant activator. Plant Diseas 85:481-

488.

Momol, M. T., S. M. Olson, J. E. Funder-

burk, J. Stavisky and J. J. Marois.

2004. Integrated management of to-

mato spotted wilt on field-grown to-

matoes. Plant Disease 88:882-890.

39

Table 1. Effects of UV-reflective plastic mulch and foliar applications of Actigard on adults of the silverleaf whitefly on tomato in 2006.

No. silverleaf whitefly adults/20 leaves

Treatment* 23 Aug 31 Aug 8 Sept 15 Sept 21 Sept 27 Sept 5 Oct 13 Oct 19 Oct 27 Oct

UV-reflective mulch alone 1b 3a 2a 2a <1a 3ab 4b 4b 2a 1a

UV-reflective mulch + Actigard 0a 2a <1a 3a 1ab 2a 1a 3a 2a 1a

White mulch alone 1b 7a 3a 3a 2b 4ab 4b 7b 2a 1a

White mulch + Actigard 0a 5a 3a 6a 2b 6b 4b 4b 3a 1a

F3,9 3.65 2.73 1.67 0.86 3.22 3.29 5.01 4.16 0.24 0.23

P-value 0.06 0.11 0.24 0.50 0.07 0.07 0.03 0.04 0.86 0.87

*A "+" indicates that products were combined.

Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 2. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

No. silverleaf whitefly eggs/10 leaflets

Treatment* 11Sept 18 Sept 26 Sept 2 Oct 9 Oct 16 Oct 23 Oct 30 Oct 6 Nov

UV-reflective mulch alone 7a 12a 3a 1a 7a 1a 0a <1a <1a

UV-reflective mulch + Actigard 7a 16a 9a 2a 4a 1a 1a 0a 1a

White mulch alone 12a 22a 5a 7a 11a 1a <1a 1a 0a

White mulch + Actigard 19a 20a 8a 6a 10a 1a <1a 1a 1a

F3,9 1.73 1.20 0.57 0.73 1.48 0.21 0.75 0.68 2.46

P-value 0.23 0.36 0.65 0.56 0.28 0.88 0.55 0.59 0.13

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 3. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

No. silverleaf whitefly 1st instars/10 leaflets

Treatment* 11Sept 18 Sept 26 Sept 2 Oct 9 Oct 16 Oct 23 Oct 30 Oct 6 Nov

UV-reflective mulch alone 2a 5a 10a 1a 3a 6a 5a 2a 1a

UV-reflective mulch + Actigard 3a 12ab 3a 4a 5a 12b 4a 4a 1a

White mulch alone 4a 18b 10a 1a 6a 8ab 5a 3a 1a

White mulch + Actigard 6a 23b 10a 3a 7a 8ab 3a 4a 5b

F3,9 0.92 3.43 0.84 1.48 1.33 4.37 0.47 0.67 3.28

P-value 0.47 0.07 0.50 0.28 0.33 0.04 0.71 0.59 0.07

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

40

Table 4. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

No. silverleaf whitefly 2nd

and 3rd instars/10 leaflets

Treatment* 11Sept18

Sept

26

Sept 2 Oct 9 Oct 16 Oct23

Oct 30 Oct6

Nov

UV-reflective mulch alone 3a 10a 9a 1a 0a 4a 5ab 5ab 3a

UV-reflective mulch + Actigard 3a 8a 6a 4a <1a 10a 3a 2a 4ab

White mulch alone 11a 22a 11a 6a 1a 6a 7ab 11b 4ab

White mulch + Actigard 3a 17a 17a 3a 1a 4a 14b 10b 7b

F3,9 2.39 0.97 0.19 1.60 0.66 0.24 3.04 5.56 3.23

P-value 0.14 0.45 0.90 0.26 0.60 0.87 0.09 0.02 0.08

*A "+" indicates that products were combined.

Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 5. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

No. silverleaf whitefly 4th instars/10 leaflets

Treatment* 11Sept18

Sept

26

Sept 2 Oct 9 Oct 16 Oct23

Oct 30 Oct6

Nov

UV-reflective mulch alone 0a 2a 1a 0a 0a 0a 0a 0a 0a

UV-reflective mulch + Actigard 0a 1a <1a 0a 0a 0a 0a 0a 0a

White mulch alone 0a 2a <1a 1a <1a 0a <1a <1a <1a

White mulch + Actigard 0a 5a 1a 0a 0a 0a 0a 0a 0a

F3,9 ---- 0.39 1.00 1.00 1.00 ---- 1.00 1.00 0.60

P-value ---- 0.76 0.44 0.44 0.44 ---- 0.44 0.44 0.63

*A "+" indicates that products were combined.

Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 6. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

No. silverleaf whitefly sessile nymphs (2nd

, 3rd, and 4

th instars)/10 leaflets

Treatment* 11Sept18

Sept26

Sept 2 Oct 9 Oct 16 Oct23Oct 30 Oct

6Nov

UV-reflective mulch alone 3a 13a 10a 1a 0a 4a 5ab 5ab 3a

UV-reflective mulch + Actigard 3a 9a 6a 4a <1a 10a 3a 2a 4a

White mulch alone 11a 24a 11a 7a 1a 6a 8ab 11b 4a

White mulch + Actigard 3a 21a 18a 3a 1a 4a 14b 10b 8a

F3,9 2.39 0.58 0.30 2.03 0.61 0.24 2.84 6.50 2.53

P-value 0.14 0.64 0.82 0.18 0.62 0.87 0.10 0.01 0.12

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

41

Table 7. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

Total no. silverleaf whitefly nymphs/10 leaflets

Treatment* 11Sept18

Sept

26

Sept 2 Oct 9 Oct 16 Oct23

Oct 30 Oct6

Nov

UV-reflective mulch alone 4a 19a 20a 1a 3a 10a 10a 7a 4a

UV-reflective mulch + Actigard 5a 21a 9a 8a 5a 22a 7a 6a 6ab

White mulch alone 15a 42a 21a 7a 7a 14a 12a 14a 5a

White mulch + Actigard 9a 44a 27a 6a 8a 12a 17a 14a 12b

F3,9 2.08 1.08 0.74 1.75 1.73 1.06 2.04 2.23 4.00

P-value 0.17 0.40 0.55 0.23 0.23 0.41 0.18 0.15 0.05

*A "+" indicates that products were combined.

Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 8. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2006.

% plants with symptoms of TYLCV

Treatment*12

Sept 22 Sept 27 Sept 5 Oct 11 Oct 19 Oct 27 Oct 1 Nov

UV-reflective mulch alone 0.4a 14.1b 28.2b 75.9b 88.9b 91.0b 97.0a 100.0

UV-reflective mulch + Actigard 0.0a 5.8a 12.0a 55.7a 69.4a 82.7a 95.5a 100.0

White mulch alone 2.1b 29.3c 40.3c 89.5c 97.5c 99.2c 100.0b 100.0

White mulch + Actigard 1.3ab 15.7b 24.2b 78.4b 90.3b 94.1b 99.6b 100.0

F3,9 3.58 46.93 20.92 16.28 32.08 22.08 6.08 ----

P-value 0.06 <0.0001 0.0002 0.0006 <0.0001 0.0002 0.02 ----

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 9. Effects of UV-reflective plastic mulch and foliar applications of Actigard on yield of tomato in 2006.

Yield/10 plants on 31 Oct

Culls Small Medium Large Extra large

Treatment* No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt (lb)

UV-reflective mulch alone 7a 2.7a 2a 0.3a 24a 5.8a 28a 8.9a 73a 35.8a

UV-reflective mulch + Actigard 5ab 1.8a 3a 0.5a 27a 6.3a 30a 9.0a 36b 15.2b

White mulch alone 4ab 1.3a 3a 0.4a 27a 6.2a 33a 10.1a 41b 18.2b

White mulch + Actigard 4b 1.2a 1a 0.2a 17a 3.9a 26a 8.4a 28b 12.4b

F3,9 3.69 2.15 1.53 2.06 2.39 2.33 0.57 0.33 4.16 4.85

P-value 0.06 0.16 0.27 0.18 0.14 0.14 0.65 0.80 0.04 0.03

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

42

Table 10. Effects of UV-reflective plastic mulch and foliar applications of Actigard on yield of tomato in 2006.

Yield/10 plants on 14 Nov

Culls Small Medium Large Extra large

Treatment* No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt (lb)

UV-reflective mulch alone 2a 0.7a 4a 0.7a 31a 7.6a 24a 7.7a 4ab 1.8ab

UV-reflective mulch + Actigard 4a 1.2a 3a 0.4a 48a 12.5a 36a 11.7a 5a 2.0a

White mulch alone 2a 0.4a 3a 0.7a 29a 7.6a 17a 5.8a 0b 0.0b

White mulch + Actigard 2a 1.0a 4a 0.9a 32a 8.0a 21a 7.0a 2ab 0.9ab

F3,9 0.95 1.07 0.56 1.23 1.61 1.77 2.70 2.67 3.01 2.91

P-value 0.46 0.41 0.66 0.35 0.25 0.22 0.11 0.11 0.09 0.09

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 11. Effects of UV-reflective plastic mulch and foliar applications of Actigard on yield of tomato in 2006.

Total yield/10 plants

Culls Small Medium Large Extra large

Treatment* No.Wt.

(lb) No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt (lb)

UV-reflective mulch alone 9a 3.5a 6a 1.0a 55a 13.4a 52a 16.6a 76a 37.5a

UV-reflective mulch + Actigard 9a 2.9a 5a 0.9a 75a 18.8a 65a 20.7a 41b 17.2b

White mulch alone 6a 1.7a 6a 1.1a 55a 13.8a 50a 15.8a 41b 18.2b

White mulch + Actigard 5a 2.2 6a 1.0a 49a 11.8a 48a 15.4a 30b 13.2b

F3,9 1.78 1.57 0.42 0.74 1.61 1.81 0.24 1.00 4.39 5.19

P-value 0.22 0.26 0.75 0.55 0.25 0.22 0.35 0.44 0.04 0.02

*A "+" indicates that products were combined.

Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 12. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2007.

No. silverleaf whitefly adults/20 leaves

Treatment* 27 March 2 April 9 April 16 April 23 April 30 April 7 May 14 May 22 May 29 May

UV-reflective mulch alone 0a <1a 3a 1a 1a 5a 1a 29a 167a 352a

UV-reflective mulch + Actigard 0a <1° 4a 0a <1a 7a 6a 17a 155a 319a

White mulch alone 0a 0a 3a 0a <1a 8a 2a 20a 122ab 325a

White mulch + Actigard 0a 0a 4a <1a 1a 12a 1a 32a 79b 331a

F3,9 ---- 0.60 0.79 1.94 1.10 1.97 1.20 2.01 4.76 0.45

P-value ---- 0.63 0.53 0.19 0.40 0.19 0.36 0.18 0.03 0.72

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

43

Table 13. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf

whitefly on tomato in 2007.

No. silverleaf whitefly eggs/10 leaflets

Treatment* 16 April 23 April 30 April 7 May 14 May 21 May 28 May

UV-reflective mulch alone 1a 10a 14a 26a 56a 54a 516a

UV-reflective mulch + Actigard 6a 11a 12a 36a 55a 81a 329a

White mulch alone 5a 10a 14a 27a 42a 183a 452a

White mulch + Actigard 5a 7a 16a 37a 80a 114a 216a

F3,9 0.84 0.93 0.14 0.51 0.19 1.96 2.50

P-value 0.51 0.46 0.93 0.68 0.90 0.19 0.13

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 14. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on

tomato in 2007.

No. silverleaf whitefly 1st instars/10 leaflets

Treatment* 16 April 23 April 30 April 7 May 14 May 21 May 28 May 4 June

UV-reflective mulch alone <1a 1a 3a 25a 17a 29ab 60a 235a

UV-reflective mulch + Actigard 1a 3a 2a 17a 36a 49ab 64a 190a

White mulch alone 3a 2a 3a 11a 18a 22a 64a 200a

White mulch + Actigard 0a 0a 1a 15a 25a 99b 47a 197a

F3,9 2.31 1.31 1.90 1.43 0.87 3.19 0.29 0.96

P-value 0.14 0.33 0.20 0.30 0.49 0.08 0.83 0.45

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 15. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on

tomato in 2007.

No. silverleaf whitefly 2nd

and 3rd instars/10 leaflets

Treatment* 16 April 23 April 30 April 7 May 14 May 21 May 28 May 4 June

UV-reflective mulch alone <1a 0a <1a 9a 15a 23a 65a 433a

UV-reflective mulch + Actigard 1a 1a <1a 4a 24a 33a 54a 278a

White mulch alone 1a 1a 5a 8a 12a 28a 63a 336a

White mulch + Actigard 1a 1a 1a 1a 11a 44a 74a 316a

F3,9 0.32 0.70 1.32 1.90 0.49 0.30 0.02 2.29

P-value 0.81 0.58 0.33 0.20 0.70 0.82 1.00 0.15

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

44

Table 16. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on

tomato in 2007.

No. silverleaf whitefly 4th instars/10 leaflets

Treatment* 16 April 23 April 30 April 7 May 14 May 21 May 28 May 4 June

UV-reflective mulch alone 0a 0a 0a <1a 3b 13a 27a 106a

UV-reflective mulch + Actigard 0a 0a 0a 0a 2ab 18a 35a 84a

White mulch alone 0a 0a 0a 0a 1ab 18a 26a 60a

White mulch + Actigard 0a 0a <1a 0a 0a 36a 32a 101a

F3,9 ---- ---- 1.00 1.00 3.44 0.45 0.83 2.45

P-value ---- ---- 0.44 0.44 0.07 0.72 0.51 0.13

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 17. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly ontomato in 2007.

No. silverleaf whitefly sessile nymphs (2nd

, 3rd, and 4

th instars)/10 leaflets

Treatment* 16 April 23 April 30 April 7 May 14 May 21 May 28 May 4 June

UV-reflective mulch alone <1a 0a <1a 10a 18a 36a 92a 538a

UV-reflective mulch + Actigard 1a 1a <1a 4a 26a 52a 89a 362a

White mulch alone 1a 1a 5a 8a 13a 46a 89a 396a

White mulch + Actigard 1a 1a 1a 1a 11a 80a 106a 417a

F3,9 0.32 0.70 1.11 2.15 2.25 0.07 0.31 2.28

P-value 0.81 0.58 0.40 0.16 0.15 0.97 0.82 0.15

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 18. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly ontomato in 2007.

Total no. silverleaf whitefly nymphs/10 leaflets

Treatment* 16 April 23 April 30 April 7 May 14 May 21 May 28 May 4 June

UV-reflective mulch alone 1a 1a 3a 34a 36a 64a 151a 773a

UV-reflective mulch + Actigard 1a 4a 2a 20ab 62a 101a 153a 552b

White mulch alone 4a 4a 8a 19ab 31a 68a 153a 596b

White mulch + Actigard 1a 1a 2a 17b 36a 179a 153a 613b

F3,9 1.05 0.87 1.13 3.23 1.30 0.92 0.32 4.79

P-value 0.42 0.49 0.39 0.08 0.33 0.47 0.81 0.03

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

45

Table 19. Effects of UV-reflective plastic mulch and foliar applications of Actigard on the silverleaf whitefly on tomato in 2007.

% plants with symptoms of TYLCV

Treatment* 11 April 17 April 25 April 2 May 9 May 16 May 24 May 31 May 8 June 15 June

UV-reflective mulch alone 0.0a 0.4a 1.3a 2.5a 4.2a 11.3a 33.8a 52.5a 64.6a 75.0ab

UV-reflective mulch + Actigard 0.0a 0.0a 0.4a 0.8a 1.3a 3.0b 16.5a 36.2a 44.3a 52.4b

White mulch alone 0.0a 0.0a 0.0a 0.4a 2.5a 6.7ab 20.5a 43.0a 50.1a 57.7ab

White mulch + Actigard 0.4a 0.4a 0.8a 3.4a 4.2a 10.2a 34.4a 64.1a 70.5a 77.4a

F3,9 1.00 0.60 0.74 1.26 0.96 3.77 2.05 2.64 2.30 3.29

P-value 0.44 0.63 0.55 0.35 0.45 0.05 0.18 0.11 0.15 0.07

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 20. Effects of UV-reflective plastic mulch

and foliar applications of Actigard on Liriomyzaon tomato in 2007.

Treatment*

No. Lirio-

myzaleafmines/2min search

UV-reflective mulch alone 73a

UV-reflective mulch + Actigard 61bc

White mulch alone 70ab

White mulch + Actigard 51c

F3,9 8.09

P-value 0.006

*A "+" indicates that products were combined.Means within a column followed by the same

letter are not significantly different by the LSD(P=0.05).

Table 21. Effects of UV-reflective plastic mulch and foliar applications of Actigard on yield of tomato in 2007.

Yield/10 plants on 4 June

Culls Small Medium Large Extra large

Treatment* No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt (lb)

UV-reflective mulch alone 17ab 6.5a 4a 0.8a 28a 6.6a 58a 19.7a 95a 42.0a

UV-reflective mulch + Actigard 10b 3.7b 5a 0.8a 34a 8.3a 48a 16.4ab 75ab 32.9ab

White mulch alone 19a 7.3a 5a 0.7a 32a 7.6a 49a 16.3ab 84a 36.6a

White mulch + Actigard 14ab 4.8ab 4a 0.6a 30a 7.3a 42a 13.3b 55b 23.7b

F3,9 3.50 4.35 0.29 0.19 0.24 0.25 2.40 2.76 5.52 5.88

P-value 0.06 0.04 0.83 0.90 0.87 0.86 0.14 0.10 0.02 0.02

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

46

Table 23. Effects of UV-reflective plastic mulch and foliar applications of Actigard on yield of tomato in 2007.

Total yield/10 plants

Culls Small Medium Large Extra large

Treatment* No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt (lb)

UV-reflective mulch alone 21a 7.6ab 46a 7.8a 70a 17.0a 89a 29.5a 104a 45.1a

UV-reflective mulch + Actigard 16a 5.2b 30a 5.2a 67a 16.8a 79a 27.4a 89ab 38.9ab

White mulch alone 23a 8.4a 40a 6.7a 69a 17.6a 72a 23.7a 95a 40.9ab

White mulch + Actigard 17a 5.8b 41a 6.7a 72a 17.6a 76a 24.7a 67b 31.2b

F3,9 2.21 3.90 1.30 1.77 0.07 0.06 2.36 2.20 4.29 2.40

P-value 0.16 0.05 0.33 0.22 0.97 0.98 0.14 0.16 0.04 0.14

*A "+" indicates that products were combined.

Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

Table 22. Effects of UV-reflective plastic mulch and foliar applications of Actigard on yield of tomato in 2007.

Yield/10 plants on 18 June

Culls Small Medium Large Extra large

Treatment* No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt. (lb) No. Wt (lb)

UV-reflective mulch alone 4a 1.1a 42a 7.1a 43a 10.4a 31a 9.8a 9a 3.2a

UV-reflective mulch + Actigard 5a 1.5a 25a 4.4a 34a 8.6a 31a 11.0a 15a 6.0a

White mulch alone 4a 1.0a 36a 6.1a 37a 10.0a 22a 7.4a 10a 4.3a

White mulch + Actigard 3a 1.0a 37a 6.1a 42a 10.4a 34a 11.4a 13a 7.5a

F3,9 0.98 0.57 1.77 2.36 1.38 1.02 1.37 1.32 1.57 0.97

P-value 0.44 0.65 0.22 0.14 0.31 0.43 0.31 0.33 0.27 0.45

*A "+" indicates that products were combined.Means within a column followed by the same letter are not significantly different by the LSD (P=0.05).

47

Control of Bacterial Spot on

Tomatoes in the Greenhouse and

Field with Kasugamycin

Ken Pernezny, Nikol Hayranek, &

Nadia Abdullah

UF/IFAS, Everglades Research and

Education Center

University of Florida

3200 E. Palm Beach Rd.

Belle Glade 33430

Pam Roberts & Rod Sytsma,

IFAS, Southwest Florida REC

2686 Hwy. 29 N.

Immokalee, FL 34142

Introduction and background

Bacterial spot, caused by Xan-

thomonas perforans, continues to be one

of the most important diseases of toma-

toes in Florida. Losses of up to 50% in

large and extra-large fruit have been

documented when epidemics begin at

flowering (Pohronezny and Volin,

1983). Control is based on cultural prac-

tices and, typically, frequent sprays of

copper and mancozeb. However, wide-

spread occurrence of copper-resistant

strains often hamper management efforts

with copper (Marco and Stall, 1983; Po-

hronezny et al., 1992). Even the addition

of mancozeb is not sufficient to over-

come resistance to copper in some

strains (Pernezny et al., 2007).

Kasugamycin is a relatively new

antibiotic available to agriculture for

management of bacterial pathogens. It is

currently available for use on tomatoes

and peppers in Mexico but not in the

United States. In work reported to the

Florida Tomato Committee in 2006, we

found preliminary evidence that kasu-

gamycin significantly reduces bacterial

spot severity on tomato plants in the

greenhouse. Therefore, we initiated these

studies to determine the efficacy of ka-

sugamycin for control of bacterial spot

of tomato both in the greenhouse and the

field.

Materials and methods

Greenhouse experiments. Ex-

periments were conducted in an air-

conditioned greenhouse at Everglades

Research and Education Center in Belle

Glade. Maximum temperatures reached

28°C at midday. Tomato seed, cv. BHN

586, were planted in 15-cm-diameter

plastic pots in a commercial potting mix

(Fafard Soil Mix No. 2). After emer-

gence, plants were fertilized once per

week with a 20-20-20 soluble fertilizer

(1 g/L) (Agriliance, Inc.).

Plants were sprayed twice with

test chemicals at a 7-day interval before

inoculation, and twice at a 7-day interval

after inoculation. Kasugamycin was

tested with and without addition of cop-

per or captan (Table 1). Specific treat-

ments were Kasumin 2L (64 fl. oz./100

gal); Kasumin 2L + Kocide 2000 (1.5

lb/100 gal); Kasumin + Captan 50WP (3

lb/100gal); Kasuran 50WP (a pre-mixed

combination of kasugamycin and copper

hydroxide) (1.7 lb/100 gal); and a water-

sprayed control.

Xanthomonas perforans strains

T193, resistant to copper, was grown for

3 days at 28°C on glucose-nutrient agar.

Plates were flooded with sterile phos-

phate-buffered saline (Leben et al.,

1968), and resultant suspensions were

adjusted trubidimetrically to approxi-

mately 1 x 108 CFU/ml. Suspensions

were diluted to 106 CFU/ml for inocula-

tion. Applications of bacterial suspen-

sions were made by misting both adaxial

and abaxial leaf surfaces to run off using

a plastic spray bottle. Two drops of

Tween 80 were added to 660 ml of in-

oculum suspension to enhance wetting

48

of leaf surfaces. Plants were covered in

plastic bags for three days after

inoculation.

The experiment was a nested de-

sign with three plants nested within each

treatment and treatments assigned ran-

domly within each of four blocks. Dis-

ease ratings were made 16 days after in-

oculation and consisted of the percent-

age of leaf surface covered with lesions

combined with that lost from premature

defoliation (Pernezny et al., 1996). The

experiment was repeated. These tests

were conducted between December 2006

and late February 2007.

Field experiment. An experi-

ment was conducted at the Southwest

Florida Research and Education Center

to evaluate the efficacy of kasugamycin

for management of bacterial spot. To-

mato seedlings, cv. Hazera 3073, were

transplanted on March 6 2007 into a

field with soil type Immokalee fine sand.

Treatments were kasugamycin (Kasumin

2L, 64 fl.oz. /100 gal); kasugamycin +

copper hydroxide (Kocide 2000, 50%

Cu, 1.5 lb/Ac); kasugamycin + Captan

50WP (3 lb/100gal); a premixed product

of kasugamycin + copper hydroxide

(Kasuran 50WP, 1.7 lb/100gal); and an

untreated control.

Treatments were arranged in a

randomized complete block design with

four replications. Each plot consisted of

15 plants spaced 1.5 ft apart with 15 ft

between each plot. Beds were 2.7 wide

on 6-ft centers and covered with black

polyethylene film. Guidelines estab-

lished by the University of Florida,

IFAS, were followed for land prepara-

tion, fertility, irrigation, and weed and

insect management. Plants were sprayed

9 times at a 7-day interval on March 20

and 27, April3, 10, 17, and 24 and May

1, 8, and 15. All test materials were ap-

plied with a high-clearance sprayer des-

ignated specifically for applications in

staked tomato plots at a tractor speed of

2 mph and a pressure of 200 psi. A dou-

ble-drop boom equipped with six noz-

zles delivered a spray volume of 66

gal/acre.

Plots were inoculated on 12 and

27 April with a suspension of the bacte-

rial spot pathogen Xanthomonas vesica-

toria, race T1 and Xanthomonas per-

forans, race T3 at a final concentration

of 1 x 108 CFU/ml with a hand-pump

sprayer. A visual assessment was made

of the percentage of foliage covered with

lesions plus that lost due to premature

defoliation combined into one rating

(Pernezny et al., 1996) on April 26 and

May 21.

All fruit were harvested once on

May 23 and the number and weight of

marketable and nonmarketable (small,

misshapen, or diseased) fruit recorded.

Disease severity ratings and yield data

were subjected to analysis of variance,

followed by mean separation using

Waller’s method at P 0.05 (Statistical

Analysis System SAS Institute,

Cary, NC).

Samples of diseased leaf tissues

were taken from each replicated plot of

the following treatments: control, kasu-

gamycin, and kasugamycin + copper hy-

droxide on April 26 and May 21. Xan-

thomonas vesicatoria (perforans) strains

were isolated to determine their sensi-

tivity to kasugamycin in vitro. Briefly, a

flamed and cooled inoculation needle

with a small right-angle bend at the tip

was inserted through the margin of dis-

eased tissue and, without removal,

streaked onto duplicate plates of nutrient

agar supplemented with 50 g/ml of cy-

cloheximide. Plates were incubated at

28°C for 3 days. Single yellow colonies

characteristic of Xanthomonas were

49

restreaked from the isolation plates on

nutrient agar containing 0.5% glucose

(GNA). Cultures were restreaked as nec-

essary to ensure purity and stored in

sterile 15% aquous glycerol at -70°C.

A total of 12 strains were isolated

on each sampling plate. These strains

were streaked on two GNA plates con-

taining 100 ppm kasugamycin and two

control plates without kasugamycin

amendment. After 3-days incubation at

28°C, growth on GNA with and without

kasugamycin was qualitatively com-

pared as a measure of strain sensitivity

to kasugamycin.

Results

The kasugamycin treatments,

with the exception of the Kasuran (kasu-

gamycin + copper hydroxide premix)

reduced bacterial spot severity on toma-

toes in the greenhouse (Table 1). While

not striking, differences between the

control and treatments with kasugamycin

were often statistically significant and

represented as much as 33% less disease

in some of the better treatments. There

did not appear to be a big advantage

gained by addition of copper or captan to

kasugamycin; these combination treat-

ments were statistically equivalent to

sprays of kasugamycin alone (Table 1).

In the first field assessment made

on plants in the Immokalee trial, kasu-

gamycin-treated plots had significantly

lower disease ratings than the control

plots (Table 2). For example, kasugamy-

cin alone had a disease rating of 10.5%

compared to 23.8% in the control plots,

less than half as much foliar damage.

However, none of the treatments con-

taining kasugamycin were any better

than the long-time grower standard, cop-

per + mancozeb.

No differences were found in any

of the yield data collected (Table 3), in-

cluding total number and weight of all

fruit harvested, number and weight of

marketable and unmarketable fruit, and

nonmarketable fruit as a percentage of

the total weight harvested.

None of the 12 strains of X. vesi-

catoria (X. perforans) collected on April

26 showed any signs of kasugamycin

resistance (Table 4). However, at least

one strain isolated on May 21 from the

kasugamycin plots was highly resistant

and several others showed some growth

on kasugamycin-amended plates.

Discussion

Under relatively low-disease

pressure in the greenhouse and the field,

kasugamycin provided a level of control

of bacterial spot of tomato. In both in-

stances, the degree of control was about

the same as that observed with the in-

dustry standard of copper + mancozeb. If

registered for use on tomatoes in the

United States, it would give growers an

alternative chemical control option that

could be rotated with copper + man-

cozeb as part of an integrated program to

manage this disease. At high-disease

pressure as experienced after the second

inoculation in the field, kasugamycin, as

well as the grower standard, did not sig-

nificantly reduced disease levels. Jones

and Jones (1985) also found that avail-

able chemical control measures were

relatively ineffective when bacterial spot

epidemics were intense.

Addition of copper as a formu-

lated additive or a tank mix option with

kasugamycin did not improve the effi-

cacy of this antibiotic. Similarly, captan

had no synergistic effect when tank-

mixed with the kasugamycin. Most of

the disease control observed in treat-

ments containing kasugamycin had to

come from the kasugamycin itself.

50

Development of resistance is a

major concern any time antibiotics are

used routinely in the field. Rapid devel-

opment of resistance to streptomycin

rendered this once promising chemical

ineffective within a few seasons on sev-

eral vegetable crops (Stall and Thayer,

1962). This resistance may be relatively

long-lived even after streptomycin use

has been discontinued (Pohronezny et

al., 1994).

A total of nice applications of

kasugamycin were made to Immokalee

tomato plots. By the end of the experi-

ment, at least one strain of the bacterial

spot pathogen was found to be highly

resistant to kasugamycin in an in vitro

screening test. Some growth on kasu-

gamycin-amended plates was observed

with several other strains. This fairly

rapid development of resistance parallels

that experienced with streptomycin in

the past. If kasugamycin does get a full

label in the US, it will have to be used

very judiciously if it is to remain a viable

option in an integrated disease manage-

ment program for bacterial spot of

tomato.

Table 1. Ratings of bacterial spot of tomato in the greenhouse with kasugamycin at the

Everglades Research and Education Center, 2006-2007 x

Percent disease y

Treatment (formulation/100gal) Exp. 1 Exp. 2

Untreated (control).................................................. 35.2 a z

36.8 a

Kasuran 50WP (1.72 lb)………………………….. 35.2 a 36.2 a

Kasumin 2L (64 fl. oz)…………………………… 27.4 b 23.0 ab

Kasumin 2L (64 fl. oz) + Captan 50WP (3 lb)........ 23.8 b 29.3 b

Kasumin 2L (64 fl. oz) + Kocide 2000 (2 lb)……... 27.6 b 28.6 b

x Experiments consisted of three tomato plants, cv. BHN586, nested within each of four

blocks for each treatment. Plants were sprayed with chemicals twice at a 7-day interval

before inoculation with a suspension of Xanthomonas perforans, strain T193 and twice

at a 7-day interval after inoculation.y Ratings consisted of a visual estimate of the percentage of foliage lost prematurely or

covered with lesions combined into one rating.z Means followed by the same letter are not statistically different, according to Waller-

Duncan’s k-ratio t-test at P# 0.05.

51

Table 2. Rations of bacterial spot severity in field plots treated with kasugamycin at Im-

mokalee, spring 2007 w

Rating (% foliar disease)x

Treatment (formulation/100gal) April 26 May 21

Untreated (control).................................................. 23.8 a y

40.5 N.S.z

Kasuran 50WP (1.72 lb)………………………….. 17.3 ab 40.0

Kasumin 2L (64 fl. oz) + Kocide 2000 (2 lb)……... 16.0 ab 33.2

Kasumin 2L (64 fl. oz)…………………………… 10.5 b 42.0

Kasumin 2L (64 fl. oz) + Captan 50WP (3 lb)........ 10.3 b 35.2

Kocide 2000 (2 lb) + Manzate 75DF (2 lb)..……... 8.0 b 28.8

w Treatments were replicated 4 times in a randomized complete block design. All plants

were inoculated with a 1 x 108 CFU/ml suspension of the bacterial spot pathogen on

April 12 and 27. Plots were sprayed 9 times on a weekly basis using a tractor-mounted

high-clearance sprayer.x Ratings consisted of a visual estimate of the percentage of foliage lost prematurely or

covered with lesions combined into one rating.y Means followed by the same letter are not statistically different, according to Waller-

Duncan’s k-ratio t-test at P# 0.05.z N.S.= no significant difference found at P # 0.05.

52

Table 3. Yield data from kasugamycin efficacy field experiment, Immokalee, spring

2007z

Treatment

Total

no.

fruit

Total

weight

fruit

(lb)

Marketable

no.

Marketable

wt. (lb)

Unmkt.

no.

Unmkt.

wt. (lb)

Percent by wt

unmkt.

Untreated (control) 123 51.0 59 24.2 64 26.8 56.6

Kocide + Mancozeb 123 53.3 76 32.7 48 20.8 38.6

Kasumin 115 50.4 61 27.8 54 22.6 45.8

Kasumin + kocide 100 41.1 57 23.2 43 18.2 42.8

Kasumin + Captan 118 51.0 74 31.0 44 25.4 39.1

kasuran 117 48.2 60 24.8 56 23.4 53.2

z All fruit per plot were harvested once on May 23. Unmarketable fruit were small, mis-

shapen, or diseased. No significant differences were found for any of the yield parame-

ters.

53

Table 4. Resistance of strains of Xanthomonas vesicatoria (perforans) to kasugamycin on

two sampling dates, Immokalee, spring 2007 y

Resistance estimatez

Treatment Rep

26 April 21 May

Untreated (control) 1

2

3

-

-

-

+

+

-

Kasumin 1

2

3

-

-

-

+++

++

+

Kasumin + Kocide 1

2

3

-

-

-

+

-

-

y Resistance based on growth of strains on plates of glucose-nutrient agar amended with

100 ppm kasugamycin compared to growth on GNA plates without kasugamycin.z Qualitative estimate of growth of bacteria on kasugamycin-amended plates were

equals no growth, + equals slight growth, and +++ equals very heavy growth. Plates

were streaked in duplicate.

Literature

Jones, J. B., Jones, J.P., 1985. The

effect of bactericides, tank mix-

ing time and spray schedule on

bacterial leaf spot of tomato.

Proc. Fla. State Hortic. Soc. 98,

244-247.

Leben, C. Daft, G.C. Schmitthenner,

A.F., 1968. Bacterial blight of

soybeans: Population levels of

Pseudomonas glycinea in rela-

tion to symptom development.

Plytopathology 50, 1143-1146.

Marco, G. M., Stall, R.E., 1983.

Control of bacterial spot of pep-

per initiated by strains of Xan-

thomonas campestris pv. vesica-

toria that differ in sensitivity to

copper. Plant Dis. 67, 779-781.

Pernezny, K., Datnoff, L. E., Muel-

ler, T., Collins, J.,1996. Losses in

fresh-market tomato production

in Florida due to target spot and

bacterial spot and the benefits of

protectant fungicides. Plant Dis.

80, 559-563.

Pernezny, K., Nagata, R., Havranek,

N., Sanchez, J. 2007. Compari-

son of two culture media for de-

termination of copper resistance

of Xanthomonas strains and their

usefulness for prediction of con-

trol with copper bactericides.

Crop Prot. 26 (in press).

Pohronezny, K., Sommerfeld, M.L.,

Raid, R.N., 1994. Streptomycin

54

resistance and copper tolerance

among strains of Pseudomonas

cichorii in celery seedbeds. Plant

Dis. 78, 150-153.

Pohronezny, K., Stall, R.E., Can-

teros, B.I, Kegley, M., Datnoff,

L.E., Subramanya, R., 1992.

Sudden shift in the prevalent race

of Xanthomonas campestris pv.

vesicatoria in pepper fields in

southern Florida. Plant Dis. 76,

118-120.

Pohronezny, K. Volin, R.B., 1983.

The effect of bacterial spot on

yield and quality of fresh market

tomatoes. HortScience 18, 69-70.

Stall, R. E., Thayer, P. L., 1962.

Streptomycin resistance of the

bacterial spot pathogen and con-

trol with streptomycin. Plant Dis.

Rep. 46, 389-392.

55

Evaluating Factors Affecting

Movement of the Silverleaf

Whitefly and Tomato Yellow Leaf

Curl Virus

David J. Schuster, James A. Taylor and

Craig D. Stanley

UF/IFAS, Gulf Coast Research and Educa-

tion Center, Wimauma

Jane E. Polston

UF/IFAS, Plant Pathology Department,

Gainesville

Sabine Grunwald

UF/IFAS, Soil and Water Science Depart-

ment, Gainesville

Abstract

The silverleaf whitefly, Bemisia ar-

gentifolii (also known as biotype B of the

sweetpotato whitefly, B. tabaci), is the key

insect pest of tomatoes in southern Florida.

Most damage associated with the whitefly is

due to the transmission of plant viruses, the

most damaging of which is tomato yellow

leaf curl virus (TYLCV). In the spring of

2006 and the spring of 2007, a 250-acre

field in Hillsborough County Florida was

used as a preliminary field site to determine

scouting techniques and monitor for silver-

leaf whiteflies and TYLCV. Whitefly adult

and nymphs density data and percent inci-

dence of plants with symptoms of TYLCV

data were collected on one geo-referenced

site per each 2.5 acres. Correlation analy-

ses indicated that early season silverleaf

whitefly adult counts made two and three

weeks previous to TYLCV incidence were

positively correlated. Reported is an evalua-

tion of geographic information systems

(GIS) and global positioning systems (GPS)

to map adult whitefly density and TYLCV

incidence. Also included are inverse dis-

tance weighted maps created by ArcMap

(ESRI, ArcGIS, ver. 9.x) graphically de-

picting TYLCV and adult whitefly densities.

Introduction

The silverleaf whitefly, Bemisia ar-

gentifolii (also known as biotype B of the

sweetpotato whitefly, B. tabaci), is an im-

portant economic pest in tropical and sub-

tropical climates. The silverleaf whitefly can

produce direct feeding damage in tomatoes,

but causes considerable yield loss in many

areas of the world due to its capability of

vectoring plant viruses. One important

sweetpotato whitefly vectored virus is to-

mato yellow leaf curl virus (TYLCV: genus

Begomovirus, family Geminiviridae).

TYLCV is vectored in a persistent manner

and causes damage to tomatoes worldwide.

Geographic information systems (GIS) and

global positioning systems (GPS) can be

used to monitor and predict the spread of

whiteflies and TYLCV, spatially and tempo-

rally.

The silverleaf whitefly has wide host

range and feeds by sucking plant juices from

the underside of leaves. Adults look like tiny

white moths and fly when the leaf is dis-

turbed. Eggs are light colored and are laid

on the underside of leaves and hatch in

around 16 to 38 days depending on envi-

ronmental conditions. Hot and dry condi-

tions can favor the whitefly and they can

disperse over long distances through wind

which can lead to whitefly/TYLCV man-

agement problems.

TYLCV can be a devastating disease

causing yield loss due to abscission of flow-

ers and severe plant stunting. Other symp-

toms include yellow (chlorotic) leaf edges,

upward leaf cupping, leaf mottling, and re-

duced leaf size. TYLCV was first recorded

in the Middle East, Africa, and Southeast

Asia. It has recently spread to the Caribbean

and into Florida by the late 1990s. TYLCV

has a broad host range from several families

including Fabaceae (common bean, lentil),

56

Malvaceae (cheeseweed), Solanaceae (to-

mato, pepper). TYLCV is not transmitted by

seed or mechanically. The TYLCV vector,

silverleaf whitefly acquires the virus as an

adult and is capable of harboring the virus

for several weeks. It takes an estimated 15-

30 minutes of feeding for the whitefly to ac-

quire the virus. After an incubation period in

the insect of about 24 hours TYLCV can be

spread to other plants. Symptom expression

in tomato is approximately 2-3 weeks.

GIS are software tools which allow

for storage, analysis, synthesis, and output

of spatial data. Georeferenced data which is

obtained by GPS can be incorporated into a

GIS, and provides the framework for geo-

statistical analysis. Historically, GIS has

been used for forest and rangeland entomol-

ogy, but recently it has been applied to man-

age insect pests in agricultural systems. Us-

ing GIS, entomologists have been able to

relate insect populations to biological vari-

ables and other features of the landscape.

Further applications include creating inter-

polation maps of insect counts at un-

sampled locations. Interpolation methods

include nearest neighbor, inverse distance

weighting, and spatial prediction models in-

cluding Kriging. GIS can also perform geo-

statistical analyses which can describe cor-

relations through space and/or time and

could be important for developing manage-

ment strategies for whiteflies and TYLCV.

Benefits of using GIS can include in-

creased visual expression of ecological vari-

ables, geostatistical analysis of spatiotempo-

ral data and applications into the manage-

ment of agricultural pests such as the sil-

verleaf whitefly/TYLCV as an area-wide

pest management system. Current objectives

include: analyze spatio-temporal data from

2006-2007 grower field site in Hillsborough

Co. Florida, evaluate correlations between

silverleaf whitefly and TYLCV, create in-

terpolation maps of un-sampled locations in

the grower’s field and acquire new field

sites to further expand research possibilities

on an area-wide scale.

Methods

In the spring of 2006 and the spring

of 2007, a 250 acre field in Hillsborough

County Florida was used as a preliminary

field site to determine proper scouting and

data collection techniques. Sampling in-

cluded adult whitefly counts (total number

of adults per 20 leaves on 6 plants), whitefly

nymphs (total number of nymphs on a ter-

minal leaflet per each of 6 plants), and

TYLCV incidence (visual inspection of 50

plants). Sample points were located 2.5

acres apart in a grid-like fashion within each

block and were georeferenced. Sampling

points were sampled twice weekly through-

out the season, although certain blocks were

planted and harvested earlier than other

blocks and were not sampled on every sam-

pling date, pesticide application kept scouts

from entering blocks, and rain events post-

poned scouting efforts.

In 2006, the grower’s field was di-

vided into blocks and the scouts sampled

randomly selected sites throughout each

block. Scouting was initiated on January 14

and continued biweekly until June 9. Data

points varied within blocks from each sam-

pling date, which created a problem using

temporal analysis data. Even though the data

points moved throughout the 2006 fall sea-

son, maps could be created and analyzed

spatially.

In 2007, the grower’s field was di-

vided into blocks but sampling points re-

mained constant throughout the season (i.e.,

the same 6 plants were scouted and the same

50 plants were evaluated for TYLCV inci-

dence). Scouting was initiated on February 2

and continued biweekly until May 25.

Spatiotemporal analysis of 2006-

2007 data was analyzed using ArcMap

(ESRI, ArcGIS, ver. 9.x). Maps were cre-

ated using ArcMap (ESRI, ArcGIS, ver. 9.x)

57

with inverse distance weighting (IDW)

which estimates predicted values based on

the distance they are away from a sampled

point. Correlations were conducted with

Pearson’s correlation analysis (SAS).

Results

From 2007, adult whitefly counts 2

weeks and 3 weeks prior to TYLCV inci-

dence were positively correlated over all

dates and sampled points (CORR = 0.71,

P = 0.0001, N = 346) (CORR = 0.68, P =

0.0001, N = 346), respectively. Other dates

were also positively correlated. Most of

these dates occurred during the early season

when adult whitefly numbers were low.

Correlations represented with a map

of interpolated values are the best way to

view georeferenced data without geostatisti-

cal analysis, as the correlations can tell us

something about the interpolated maps. Fig-

ures 1, 2, 3, and 4 show two dates of

TYLCV incidence overlaid with contour

maps of interpolated adult whitefly counts.

TYLCV incidence is the solid color scheme

with the adult whitefly density as the con-

tour or isolines. Figure 1a depicts the corre-

lation of TYLCV incidence on February 27,

2007 and adult whiteflies 21 days before

(CORR = 0.77, P = 0.0052, N = 11). Figure

1b graphically depicts the correlation of

TYLCV incidence on February 27, 2007 and

adult whiteflies 14 days before (CORR =

0.93, P = 0.0001, N = 11). Notice the hot

spots or bulls eyes of adult whiteflies that

aren’t represented by TYLCV as indicated

in Figure 1a and 1b by arrows. Figure 2a

describes the correlation of TYLCV inci-

dence on March 2, 2007 and adult whiteflies

21 days prior (CORR = 0.77, P = 0.0052, N

= 11). Figure 2b illustrates the correlation of

TYLCV incidence on March 2, 2007 and

adult whiteflies 17 days prior (CORR =

0.93, P = 0.0001, N = 11). Figure 3a shows

the correlation of TYLCV incidence on

April 13 and adult whiteflies 21 prior

(CORR = 0.43, P = 0.13). Figure 3b shows

the correlation of TYLCV incidence on

April 13 and adult whiteflies 14 days before

(CORR = 0.29, P = 0.38). Figure 4a shows

the correlation of TYLCV incidence on May

8 and adult whiteflies 20 days prior (CORR

= -0.23, P = 0.49). Figure 4b shows the cor-

relation of TYLCV incidence on May 8 and

adult whiteflies 14 days before (CORR = -

0.05, P = 0.87). Note the change of scale in

all figures.

Discussion

Early season scouting dates showed

the highest correlations. Also, correlations

between adult whitefly counts 2 and 3 weeks

before TYLCV incidence were most impor-

tant due to the length of time between in-

oculation and symptom expression. These

correlations varied in significance over dates

throughout the season and within short time

frames (i.e., significant at 14 days, not sig-

nificant at 17, and then significant at 21

days). Variation was inevitable as TYLCV

incidence data were held constant and bio-

logical factors such as weather, crop phe-

nology, or insecticide applications could in-

fluence the distribution of whiteflies. Also,

whitefly density may not have direct impact

on TYLCV spread as one viliferous whitefly

can spread TYLCV to multiple plants.

Figure 1a and 1b show whitefly hot-

spots (arrows) that aren’t represented by

TYLCV. This indicates that not all whitefly

populations within the field are viliferous.

These hotspots continue throughout the sea-

son. Also, notice that there are virus hot-

spots that aren’t depicted with adult

whiteflies. The viliferous whiteflies that

caused these virus hotspots could have been

killed/moved by insecticides, moved by

wind, or moved due to changing crop phe-

nology within the field. Note the scale of

TYLCV incidence in Figures 1 and 2 and

see how TYLCV incidence increased as the

epidemic progresses into April (Fig. 3). We

58

can see that the early season patch of

TYLCV (Figures 1 and 2) is not represented

in the later season (Figures 3 and 4), indi-

cating that the initial source of TYLCV and

whiteflies may not have impacted the larger

infection area around the northeast quadrant

of the field. This implicates that there was

more than one area of initial whitefly and

virus spread. The interpolated maps from the

end of the season suggest an influx of virus

coming from the northeast and moving

down and across the field. A more thorough

knowledge of the distribution of the virus in

the environment and/or movement of secon-

dary spread throughout the field will have to

be evaluated. Also, wind direction and speed

will be evaluated to determine their effect on

whitefly dispersal and subsequent virus

spread.

From the figures, we see the graphi-

cal mapping power of GIS, but also some of

the limitations in using it as a single analyti-

cal tool. We can see from the interpolated

maps created by IDW that bulls eyes are

created around data points. This is an inher-

ent problem with using IDW. It’s a good

first tool at viewing the data visually, but

IDW can be misleading. To solve this prob-

lem future research will be conducted using

spatial prediction models that can deal with

the statistical relationships of the data. These

methods include Kriging, which uses auto-

correlation or the statistical relationship

among measured points to create its inter-

polation maps. Kriging also has the ability to

create a standard error map that would give

us some measure of the accuracy of the pre-

diction surface. Kriging allows for the trans-

formation of the data if needed. In general,

Kriging allows for much more flexibility

over IDW in data presentation but is inher-

ently more complicated.

We will use the 2.5 acre sample size

distribution again for future research as it

gave us the spatial resolution needed to cre-

ate interpolation maps at the field scale. One

of the largest factors in deciding the amount

and intensity of sample size is the monetary

costs of those samples. Our sampling meth-

ods are time intensive and it takes two qual-

ity scouts a full day to take 125 samples or

one field 250 acres. To add more acreage

to our program, which would be required for

an area-wide management program, we

could either alter our scouting intensity and

reduce the resolution of created interpolation

and geostatistical analysis, or add scouts.

These are both problematic as the introduc-

tion of scouts increases variability in scout-

ing data and increases monetary costs, and

decreasing the scouted samples per area

would reduce resolution on the field scale in

our analysis. This has implications on how

we would conduct this research program for

managing whiteflies and TYLCV at the field

level or expansion into an area-wide man-

agement program.

There is importance in understanding

whitefly dispersal and TYLCV spread. GIS

gives us the power to both graphically visu-

alize and analyze the field data using geo-

statistics. By expanding our research with

more fields we might be able to add to our

current management program by better un-

derstanding where silverleaf whiteflies and

TYLCV originate and how they move

through the field.

59

Figure 1. Inverse distance weighting (IDW) maps of adult whitefly density overlaid on TYLCV

incidence from selected dates in 2007.

A

E

60

Figure 2. Inverse distance weighting (IDW) maps of adult whitefly density overlaid on TYLCV

incidence from selected dates in 2007.

A

B

61

Figure 3. Inverse distance weighting (IDW) maps of adult whitefly density overlaid on TYLCV

incidence from selected dates in 2007.

A

B

62

Figure 4. Inverse distance weighting (IDW) maps of adult whitefly density overlaid on TYLCV

incidence from selected dates in 2007.

A

B

63

Monitoring Resistance of the

Silverleaf Whitefly to Insecticides

David J. Schuster

UF/IFAS, Gulf Coast Research and Educa-

tion Center, Wimauma

Mark A. Mossler

UF/IFAS, Pesticide Information

Office, Gainesville

Abstract

Resistance monitoring for the neoni-

cotinoids Admire and Platinum for the sil-

verleaf whitefly (SLWF), Bemisia argenti-

folii Bellows & Perring was continued in

2007. Monitoring for resistance to the

neonicotinoids Assail and Venom, the py-

rethroids bifenthrin, and the chlorinated hy-

drocarbon endosulfan were initiated in 2007.

Resistance to the neonicotinoids was esti-

mated in the laboratory using a cut leaf peti-

ole bioassay method and resistance to the

pyrethroids and chlorinated hydrocarbons

was estimated using a residual vial bioassay

method. All bioassays were conducted using

adults reared from foliage infested with

nymphs that had been collected from each

crop field. Standard probit analyses were

used to estimate the LC50 values for a labo-

ratory colony and for each field population.

The relative susceptibility (RS50) of each

field population was calculated by dividing

the LC50 values of the field populations by

the LC50 value of the laboratory colony. The

average RS50 value for Admire for 2007 de-

creased from 2006 about 30% while that for

Platinum decreased about 60%. One popu-

lation was particularly high for Admire with

an RS50 value of 85.8. All populations

evaluated were susceptible to Venom and

Assail. Five of the six populations evaluated

for susceptibility to bifenthrin were highly

resistant with an average RS50 value of

about 141, while the seven populations

evaluated with endosulfan were susceptible

with an average RS50 value of 1.7. The re-

sults emphasize more than ever that growers

should strictly observe the guidelines for

managing the silverleaf whitefly, whitefly

vectored plant viruses, and insecticide re-

sistance.

Introduction

The silverleaf whitefly (SLWF), Be-

misia argentifolii Bellows & Perring [also

known as biotype B of the sweetpotato

whitefly, B. tabaci (Gennadius)] and tomato

yellow leaf curl virus (TYLCV) remain the

key pests of tomatoes in southern Florida.

Insecticides, particularly the neonicotinoids

(Admire Pro®, imidacloprid, Bayer Crop-

Science, Research Triangle Park, NC; As-

sail®, acetamiprid, Cerexagri Inc., King of

Prussia, PA; Platinum®, thiamethoxam,

Syngenta Crop Protection, Inc., Greensboro,

NC; and Venom®, dinotefuran, Valent

U.S.A. Corp., Walnut Creek, CA), remain

integral tools for the management of the

pests. Because of the potential of the

whitefly to develop resistance to the insecti-

cides, a program to monitor the susceptibil-

ity of field populations of the SLWF to Ad-

mire and Platinum using a cut leaf petiole

method was conducted from 2000 to 2006

(Schuster and Thompson 2001, 2004;

Schuster et al. 2002, 2003, 2006). Suscepti-

bility of the SLWF to Admire decreased

from 2000 to 2003, increased in both 2004

and 2005, and then decreased tremendously

in 2006. Susceptibility of the SWLF to

Platinum decreased from 2003 to 2005 and

then, as with Admire, susceptibility de-

creased dramatically in 2006. Because of the

reduced susceptibility indicated in 2006, the

resistance monitoring program was contin-

ued in 2007 and expanded to include the

other neonicotinoids Assail and Venom as

well as pyrethroids and chlorinated hydro-

carbons.

64

Materials and Methods

Resistance to the neonicotinoids was

estimated in the laboratory using a cut leaf

petiole bioassay method (Schuster and

Thompson 2001, 2004; Schuster et al. 2002,

2003, 2006). Cotton seedlings grown under

insect-free greenhouse conditions were used

at the two true leaf stages. The petioles of

the cotton leaves were cut and placed imme-

diately in the vials containing seven differ-

ent concentrations of insecticides (viz; 10.0,

5.0, 2.5, 1.25, 0.625, 0.3125, 0.15625 ppm

and control (de-ionized water). The petioles

were immersed individually in the insecti-

cide solutions for 24 hrs. After 24 hrs., ten

whitefly adults were confined on the under-

side of each leaf with clip cages (2 cm di-

ameter, 1 cm high) for another 24 hrs. The

mortality was assessed by tapping the ab-

domen of the whitefly adults and observing

the movements under a microscope. Mortal-

ity was defined as any adults that were un-

able to coordinate their movements and,

hence, was unable to walk or fly.

Resistance to the pyrethroids and

chlorinated hydrocarbons was estimated us-

ing a residual vial bioassay method. Bifen-

thrin was selected as a representative pyre-

throid and endosulfan as a chlorinated hy-

drocarbon. Serial dilutions of bifenthrin and

endosulfan as technical grade compounds

were made with methanol at 1000, 300, 100,

30, 10, 3, 1 and 0.3 ppm, and 0.24ml of each

dilution was pipetted individually into sepa-

rate 20 ml vials. The vials were placed on a

hot dog roller, which had the heating ele-

ment disconnected, and placed under a fume

hood. The vials were rotated for about 15-25

minutes until the methanol had evaporated.

The vials were capped and stored at room

temperature until use. To conduct the bioas-

says, 10 whitefly adults were carefully aspi-

rated into each vial of each concentration

and capped with a ventilated lid. The vials

were held upright in a temperature con-

trolled room for 6 hr when mortality was

determined. Mortality was defined as adults

that could move but were unable to fly

and/or leave the bottom of the vial when

gently touched with a fine paintbrush. There

were 3-4 replications (vials) for each con-

centration for each population.

All bioassays were conducted using

adults reared from foliage infested with

nymphs that had been collected from each

crop field. In some cases, the populations

were maintained in the laboratory for two to

three generations in order to obtain enough

adults to conduct the bioassays. Standard

probit analyses (SAS Institute 1989) were

used to estimate the LC50 values (the con-

centration estimated to kill 50% of the

population) for a laboratory colony and for

each field population. The laboratory colony

used as a susceptible standard in this study

has been in continuous culture since the late

1980s without the introduction of whiteflies

collected from the field and, therefore,

would be expected to be particularly sus-

ceptible to insecticides. The relative suscep-

tibility (RS50) of each field population com-

pared to the laboratory colony was calcu-

lated by dividing the LC50 values of the field

populations by the LC50 value of the labo-

ratory colony. Increasing values greater than

1 suggest decreasing susceptibility in the

field population. While values approaching

8 could indicate decreasing susceptibility of

the whiteflies, such variability is not unex-

pected when comparing field-collected in-

sects with susceptible, laboratory-reared in-

sects. Values of 10 or greater, especially

those of 20 or higher, are sufficiently high to

draw attention.

Results and discussion

The average RS50 value for Admire

for 2007 decreased from 2006 about 23%

while that for Platinum decreased about 60%

(Fig. 1). One population, NECollier, was

particularly high for Admire with an RS50

value of 85.8 (Table 1). This is the highest

60

RS50 ever identified in 8 years of monitor-

ing, especially considering that the popula-

tion had been reared for two generations (3rd

generation) in the lab without further expo-

sure to Admire. Research in the past has in-

dicated that reduced susceptibility declines

as the whiteflies are reared on successive

generations of plants not treated with Ad-

mire (Schuster and Thompson 2004). The

NECollier population was also higher for

Platinum. Some other populations were also

high for both Admire and Platinum includ-

ing Homestead, SWFREC (Southwest Flor-

ida Research & Education Center, Immoka-

lee), and TR 3. However, there were two

populations that were higher for Platinum

but not Admire (Apollo Beach and

TomG#2) and one that was higher for Ad-

mire but not Platinum (Parrish-1). These re-

sults may suggest that there isn’t cross toler-

ance between the two neonicotinoids but

that there may be simultaneous selection for

tolerance. Previous monitoring had sug-

gested a similar conclusion (Schuster and

Thompson 2004). All 10 populations evalu-

ated for susceptibility to Venom were sus-

ceptible, even some populations that were

higher for Admire and/or Platinum. The six

populations evaluated with Assail were sus-

ceptible, although some, especially NECol-

lier, were higher with either Admire and/or

Platinum.

Five of the six populations evaluated

for susceptibility to bifenthrin were highly

resistant, with RS50 values greater than 100,

even though five of six were evaluated in the

third generation (Table 1). All seven popu-

lations evaluated for susceptibility to endo-

sulfan were highly susceptible, with RS50

values all less than 3, although all but one

were evaluated in the third or fourth genera-

tion.

The results emphasize that, even

though average RS50 values for Admire and

Platinum declined from 2006 to 2007, there

still remain some populations that are prob-

lematic. At least one population, NECollier,

could be classified as resistant. With the ac-

tive ingredient of Admire, imidacloprid, no

longer under patent protection, the prolif-

eration of generic formulations of imidaclo-

prid can be expected and is already occur-

ring. This not only will likely cause prices

for products containing imidacloprid to de-

crease, but will also likely result in reduced

prices for the other neonicotinoids. Reduced

costs of neonicotinoids could cause growers

to use higher rates of the products and/or

tempt them to make multiple applications.

Because of this new threat to the sustain-

ability of the neonicotinoids coupled with

the high level of resistance observed for the

pyrethroid bifenthrin, growers are encour-

aged even more than ever to strictly observe

the guidelines for managing the silverleaf

whitefly, whitefly vectored plant viruses,

and insecticide resistance that have been

formulated and promoted by the University

of Florida, and representatives of the ag-

richemical, commodity, and consultant in-

dustries (Schuster et al. 2007). Chief among

these guidelines is the establishment of a

minimum two-month crop-free period dur-

ing the summer off-season and the creation

of a crop-free break in time and/or space

between fall and spring crops. Growers

should also use the pyrethroids judiciously.

If growers fail to adhere strictly to the

whitefly management guidelines, they can

only expect levels of tolerance/resistance to

increase and difficulty in managing

whiteflies and TYLCV to escalate.

Acknowledgments

The authors wish to express their ap-

preciation to Sabrina Spurgeon and Aaron

Shurtleff for conducting the 2007 bioassays;

to Phil Stansly, Dak Seal, Henry Yonce,

Sarah Hornsby and Leon Lucas for identi-

fying and/or collecting whitefly samples for

the 2007 monitoring; and to Bayer Crop-

Science, Cerexagri Inc., Syngenta Crop

61

Protection, Valent Agricultural Products and

the Florida Tomato Committee for providing

funding for the neonicotinoid resistance

monitoring. Appreciation also is expressed

to representatives of the Florida Tomato

Committee, Florida Fruit and Vegetable As-

sociation, Bayer CropScience, Syngenta

Crop Protection, Cerexagri Inc., Glades

Crop Care, Agricultural Crop Consulting,

Agri-Tech Services, KAC Agricultural Re-

search, and Integrated Crop Management,

and to UF/IFAS personnel Alicia Whidden,

Gene McAvoy, Jim Price and Phil Stansly

for their participation in the Resistance

Management Working Group and for their

many contributions to the whitefly and re-

sistance management recommendations.

References Cited

SAS Instititute Inc. 1989. SAS/STAT User’s

Guide, Version 6, Fourth Edition,

Vol. 2, SAS Institute Inc., Cary, NC.

Schuster, D. J. and S. Thompson. 2001.

Monitoring susceptibility of the sil-

verleaf whitefly to imidacloprid, pp.

16-18. In P. Gilreath and C. S.

Vavrina [eds.], 2001 Fla. Tomato In-

stitute Proc., Univ. Fla., Gainesville,

PRO 518.

Schuster, D. J. and S. Thompson. 2004. Sil-

verleaf whitefly resistance manage-

ment update, pp. 19-25. In P. Gil-

reath and W. H. Stall [eds.], Fla.

Tomato Institute Proc., Univ. Fla.,

Gainesville, PRO 521.

Schuster, D. J., S. Thompson, P. A. Stansly

and J. Conner. 2002. Update on in-

secticides for whitefly and leafminer

control, pp. 51-60. In P. Gilreath and

C. S. Vavrina [eds.], 2002 Fla. To-

mato Institute Proc., Univ. Fla., PRO

519.

Schuster, D. J., S. Thompson and P. R. Gil-

reath. 2003. What’s up with all these

whiteflies?, pp. 12-19. In P. Gilreath

and W. H. Stall [eds.], Fla. Tomato

Institute Proc., Univ. Fla., PRO 520.

Schuster, D. J., R. Mann and P. R. Gilreath.

2006. Whitefly resistance update and

proposed mandated burn down rule.

Pp. 24-28. In K. Cushman and P.

Gilreath [eds.], Fla. Tomato Institute

Proc., Univ. Fla., PRO 523.

Schuster, D. J., P. A. Stansly, J. E. Polston,

P.s R. Gilreath and E. McAvoy.

2007. Management of whiteflies,

whitefly-vectored plant virus, and in-

secticide resistance for vegetable

production in southern Florida. Univ.

Fla., IFAS, Fla. Coop. Ext. Serv.,

ENY-735 (IN695),

http://edis.ifas.ufl.edu

62

0

5

10

15

20

25

30

35

2000 2001 2002 2003 2004 2005 2006 2007

Avg

RS

50

9 (2) 14 (4) 10 (8)

6.7

9.9

14.7

3.7

3 (0) 11 (1)

6.1

2 (0)

2.5

29.9

7 (6)

Fig. 1. Monitoring relative susceptibility (RS 50 ) of whitefly adults from

nicotinoid -treated crops to Admire (A) or Platinum (B) using a laboratory

bioassay. Numbers at the top of the bars are the average RS 50 values and

the numbers inside the bar are the number of populations bioassa yed and

the number with RS 50 values >10 (in parentheses).

0

5

10

15

20

25

30

2003 2004 2005 2006 2007

27.2

6.1

2.01.85 (4)7 (1)3 (0)8 (0)

A

B

Avg

RS

50

14 (8)

23.1

16 (8)

11.1

63

Table 1. Results of resistance bioassays of silverleaf whitefly populations collected from west central, southwest and southeast Florida

to neonicotinoid, pyrethroid, and chlorinated hydrocarbon insecticides, Spring 2007.

Neonicotinoids Pyrethroid Chlorinated

Population Generation Admire Assail Platinum Venom Bifenthrin Endosulfan

site Crop Tested1

LC50 RS50 LC50 RS50 LC50 RS50 LC50 RS50 LC50 RS50 LC50 RS50

GCREC/Lab Tomato ---- 0.38 ---- 0.58 ---- 1.36 ---- 0.32 ---- 0.06 ---- 6.79 ----

GCREC/Lab2 Tomato ---- 0.56 ---- ---- ---- 1.70 ---- ---- ---- ---- ---- ---- ----

Apollo Beach Tomato 1st 2.75 7.3 ---- ---- 13.8 10.2 1.25 4.0 7.282

116.4 19.3 2.8

Collier-2 Tomato 2nd ---- ---- ---- ---- 25.4 18.7 ---- ---- ---- ---- ---- ----

F1 Tomato 2nd 11.73

30.9 ---- ---- 10.4 7.7 ---- ---- ---- ---- 10.13

1.5

FM Eggplant 1st 2.13 5.6 ---- ---- 6.58 4.8 ---- ---- ---- ---- 9.693

1.4

Homestead Tomato 2nd 10.73

28.3 ---- ---- 29.8 21.9 ---- ---- 1.873

29.8 9.073

1.3

HomesteadB Bean 2nd ---- ---- ---- ---- 4.37 3.2 ---- ---- ---- ---- ---- ----

HSRC Tomato 2nd ---- ---- ---- ---- 3.83 2.8 ---- ---- ---- ---- ---- ----

Myakka-1 Tomato 2nd 9.603

25.32 1.424

2.5 6.15 4.5 ---- ---- ---- ---- 10.04

1.5

Maykka-5 Tomato 1st ---- ---- 2.16 3.7 5.30 3.9 1.39 4.4 ---- ---- ---- ----

NECollier Tomato 2nd 32.53

85.8 0.683

1.2 31.1 22.9 ---- ---- 6.933

110.8 8.583

1.3

P 1&2 Potato 1st 1.01 1.8 1.602

2.8 24.82

18.2 1.192

3.8 ---- ---- ---- ----

P 9 Pepper 1st 3.20 5.70 ---- ---- 3.83 2.3 1.312

4.1 ---- ---- ---- ----

Parrish-1 Tomato 1st 18.12

47.8 ---- ---- 8.82 6.5 2.21 7.0 15.13

240.9 10.83

1.6

SWFREC Watermelon 2nd 12.6 33.2 0.773

1.3 29.7 21.8 2.242

7.1 14.63

233.6 11.283

1.7

SWHendry Tomato 2nd 11.2 29.6 2.28 3.9 ---- ---- ---- ---- 7.133

114.1 ---- ----

T 5 Tomato 1st 2.43 4.33 ---- ---- ---- ---- 1.702

5.4 ---- ---- ---- ----

T 6 Tomato 2nd ---- ---- ---- ---- 8.00 5.9 1.28 4.0 ---- ---- ---- ----

TG12N Tomato 2nd ---- ---- ---- ---- ---- ---- 1.61 5.1 ---- ---- ---- ----

TomG#2 Tomato 1st 2.08 5.5 ---- ---- 14.3 10.5 0.90 2.8 ---- ---- ---- ----

TR 3 Tomato 1st 4.67 12.3 ---- ---- 19.7 14.5 ---- ---- ---- ---- ---- ----

1The first generation would be those whitefly adults emerging from the foliage collected in the field. The second and third generations

were reared on tomato plants in the laboratory that had not been treated with neonicotinoid.2The populations were tested in the 2

nd generation.

3The population was tested in the 3

rd generation.

4The population was tested in the 4

th generation.

64