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FLUENSULFONE EFFICACY TO MANAGE ROOT-KNOT NEMATODES ON DRIP-IRRIGATED FRESH-MARKET TOMATOES AND SPATIAL DISTRIBUTION IN SANDY

SOILS USING SEEPAGE IRRIGATION

By

GILMA XIOMARA CASTILLO LICONA

A THESIS PRESENTED TO THE GRADUATE SCHOOL

OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF SCIENCE

UNIVERSITY OF FLORIDA

2017

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© 2017 Gilma Xiomara Castillo Licona

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To Manuel Lindekeit, who rejoiced and suffered alongside me throughout this journey

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ACKNOWLEDGMENTS

All my efforts, sufferings, and joys are dedicated to my parents and

grandparents, the four pillars of my life, who taught me that a true leader requires

humility and the virtue of respect for others.

I would like to thank my academic advisor, Dr. Monica Ozores-Hampton for the

opportunity of pursuing a master’s degree and for her diligent supervision during this

process, and I thank my committee members Dr. Donald Dickson and Dr. Dakshina

Seal for their immensurable support.

With a heart full of gratitude, I also dedicate this work to all my colleagues and

friends: Aline Coelho Frasca, Dr. Luther Carson, Joel Mendez, Zurima Luff, Dr.

Francesco Di Gioia, Rodney Robideaux, Thaisa Marques Cantele, Alisheikh Atta, Qiang

Zhu, Xulin Chen, Shawron Weingarten, and Alexander Tasi, who not only shared their

knowledge, talent, and skills, but also placed a smile on my face during the hardest

times.

I especially would like to thank West Coast Tomatoes, Jessie Watson, Dr. Kamal

Mahmoud, and their team members for their help and assistance with crop care and

data collection. I am also thankful to University of Florida and the Southwest Florida

Research and Education Center family not only for contributing to my education and

professional enhancement, but also for their contribution to shaping my character.

Throughout this journey, I learned the importance of the virtue of generosity. A

generous human being has the ability to transcend superficiality and leave an

unforgettable trace in people’s lives.

Finally, I would like to thank ADAMA Agricultural Solutions Ltd., Danny Karmon,

Pablo Navia, and Dr. Eran Segal for their sponsorship and help provided.

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TABLE OF CONTENTS

page

ACKNOWLEDGMENTS .................................................................................................. 4

LIST OF TABLES ............................................................................................................ 7

LIST OF FIGURES .......................................................................................................... 8

LIST OF ABBREVIATIONS ............................................................................................. 9

ABSTRACT ................................................................................................................... 11

CHAPTER

1 INTRODUCTION AND LITERATURE REVIEW ..................................................... 13

Introduction ............................................................................................................. 13

Hypothesis .............................................................................................................. 17 Objectives ............................................................................................................... 17

Literature Review .................................................................................................... 18 Root-Knot Nematodes: Disease Cycle of a Global Plant Pathogen ................. 18 Alternatives for Root-Knot Nematode Management in Vegetable Production .. 19

Cultural practices ....................................................................................... 19 Chemical management .............................................................................. 20

Fluensulfone, a Recent Introduction of New Chemistry for Management of Root-Knot Nematodes ................................................................................... 22

Modeling Pre-Plant-Incorporated Fluensulfone with HYDRUS 2D/3D Using Seepage Irrigation ......................................................................................... 23

2 EFFECTS OF FLUENSULFONE AND SOIL FUMIGATION ON ROOT-KNOT NEMATODES AND FRUIT YIELD OF DRIP-IRRIGATED FRESH-MARKET TOMATO ................................................................................................................ 26

Introduction ............................................................................................................. 26 Materials and Methods............................................................................................ 29

Field Preparation and Treatment Application ................................................... 29

Data Collection ................................................................................................. 31

Statistical Analysis ............................................................................................ 32 Results .................................................................................................................... 33

Weather Conditions .......................................................................................... 33

Plant Vigor, Root-Knot Nematode Soil Density, and Root Galling .................... 33 Tomato Fruit Yield and Grade Distribution ....................................................... 34

Discussion .............................................................................................................. 34 Summary ................................................................................................................ 36

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3 EVALUATION OF FLUENSULFONE ON SOIL SPATIAL DISTRIBUTION AND MOVEMENT, PLANT GROWTH, FRUIT YIELD, AND POSTHARVEST QUALITY OF TOMATO USING SEEPAGE IRRIGATION ...................................... 41

Introduction ............................................................................................................. 41 Materials and Methods............................................................................................ 43

Field Preparation and Treatment Application ................................................... 43 Data Collection ................................................................................................. 45 Statistical Analysis ............................................................................................ 47

Results .................................................................................................................... 48 Weather Conditions, Water Table Depth, and Soil Water Matric Potential ....... 48 Fluensulfone Concentration and HYDRUS 2D/3D Modeling ............................ 49 Plant Growth, Fruit Yield, and Postharvest Quality ........................................... 50

Discussion .............................................................................................................. 52 Summary ................................................................................................................ 54

LIST OF REFERENCES ............................................................................................... 65

BIOGRAPHICAL SKETCH ............................................................................................ 75

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LIST OF TABLES

Table page 1-1 Current fumigant and non-fumigant nematicides available in Florida to

manage plant-parasitic nematodes on vegetables. ............................................ 25

2-1 Summary of minimum, mean, and maximum daily average air and soil temperatures and total rainfall accumulation during the fall of 2014, the spring of 2016, and 10-year fall and spring averages for Myakka City, FL. ........ 38

2-2 Effect of pre-plant drip-injected fluensulfone on plant vigor, root-knot nematode soil population density, and root galling index in tomato grown during the fall of 2014 and the spring of 2016 in Myakka City, FL. ..................... 39

2-3 First, second, third, and total season marketable and unmarketable tomato fruit yield in response to pre-plant drip-injected fluensulfone during the fall of 2014 and the spring of 2016 in Myakka City, FL. ................................................ 40

3-1 Summary of minimum, mean, and maximum daily average air temperatures, solar radiation, total rainfall, and evapotranspiration during the spring and fall of 2016, and 10-year spring and fall averages for Immokalee, FL. ..................... 56

3-2 Effect of pre-plant application of fluensulfone on plant dry biomass on seepage-irrigated fresh-market tomato crops grown during the spring and fall seasons of 2016 in Immokalee, FL. .................................................................... 62

3-3 Effect of pre-plant application of fluensulfone on first, first and second harvests combined, and total harvest marketable and unmarketable tomato fruit yield during the spring and fall seasons of 2016 in Immokalee, FL. ............ 63

3-4 Fluensulfone treatment effects on tomato fruit firmness (expressed as fruit deformation), exterior fruit color, pH, and total soluble solids at first harvest during the spring and fall seasons of 2016 in Immokalee, FL. ............................ 64

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LIST OF FIGURES

Figure page 3-1 Water table level (centimeters from the top of the bed) observed in seepage-

irrigated fresh-market tomato crops grown during the spring and fall seasons of 2016 in Immokalee, FL.. ................................................................................. 57

3-2 Soil water matric potential observed in seepage-irrigated tomato crops grown during the spring and fall seasons of 2016 in Immokalee, FL. ............................ 58

3-3 Fluensulfone concentration in the soil profile at 0-10 and 10-20 cm deep from the top of the bed observed in seepage-irrigated fresh market tomatoes during the spring and fall seasons of 2016 in Immokalee, FL. ............................ 59

3-4 HYDRUS 2D/3D simulation describing water flow and fate of fluensulfone treatments at 6, 20, 30 days after treatment application (DAA) under seepage irrigation conditions during the spring of 2016 in Immokalee, FL. ....................... 60

3-5 HYDRUS 2D/3D simulation describing water flow and fate of fluensulfone treatments at 8, 21, 30 days after treatment application (DAA) under seepage irrigation conditions during the fall of 2016 in Immokalee, FL. ............................ 61

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LIST OF ABBREVIATIONS

ANOVA Analysis of Variance

AZ Arizona

CA California

CEC Cation exchange capacity

CO2 Carbon Dioxide

CSB Chemical Safety Board

DAA Days after application

DAFH Days after first harvest

DAT Days after transplanting

DW Dry weight

EC Electrical conductivity

EPA Environmental Protection Agency

ET Evapotranspiration

FAO United Nations Food and Agriculture Organization

FAWN Florida Automated Weather Network

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act

FL Florida

GA Georgia

ID Idaho

IL Illinois

IN Indiana

J2 Second-stage juveniles

K Potassium

LC/MS-MS Liquid chromatography tandem mass spectrometry

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K2SO4 Potassium sulfate

MA Massachusetts

Max Maximum

MeBr Methyl bromide

Min Minimum

N Nitrogen

NH4NO3 Ammonium nitrate

NC North Carolina

OM Organic matter

P Phosphorus

Pic-Clor 60 1,3-dichloropropene plus chloropicrin (40:60, w/w)

PVC Polyvinyl chloride

RHU Representative harvest unit

RKN Root-knot nematode

SWFREC Southwest Florida Research and Education Center

TSS Total soluble solids

UF/IFAS University of Florida/Institute of Food and Agricultural Sciences

UF/SWFREC University of Florida/Southwest Florida Research and Education Center

U.S. United States

USDA United States Department of Agriculture

WI Wisconsin

1D One dimensional

2D/3D Two- and three-dimensional

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science

FLUENSULFONE EFFICACY TO MANAGE ROOT-KNOT NEMATODES ON DRIP-

IRRIGATED FRESH-MARKET TOMATOES AND SPATIAL DISTRIBUTION IN SANDY SOILS USING SEEPAGE IRRIGATION

By

Gilma Xiomara Castillo Licona

May 2017

Chair: Monica Ozores-Hampton Major: Horticultural Sciences

Florida is the leading state for production of fresh-market tomatoes (Solanum

lycopersicum L.) with 13,030 ha harvested in 2015. The evaluation of chemistries for

new management options became critical after the banning of methyl bromide (MeBr)

and the pressure of root-knot nematodes (RKNs, Meloidogyne spp.). Soil fumigants

such as Pic-Clor 60 [1,3-dichloropropene plus chloropicrin (40:60, w/w)] have been

identified as main alternatives to MeBr; however, RKN management still remains a

challenge. Fluensulfone (Nimitz, ADAMA) is a non-fumigant with a new mode of action

for soil nematode management. Fluensulfone can be soil applied from 2.0 to 2.8 kg

a.i.·ha-1 by drip irrigation or incorporated into the soil by band or broadcast application,

requiring a water application at least two days after application to avoid seedling

exposure to phytotoxic levels (≤1.0 mg·kg-1). The distribution and movement of

fluensulfone in sandy soils irrigated using seepage is still unknown. Therefore, the

objectives of these studies included evaluating the effects of Pic-Clor 60 followed by

fluensulfone on tomato plant vigor, RKN soil population density, root galling index, and

fruit yield using drip irrigation; and evaluating the soil distribution and movement of

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fluensulfone using seepage irrigation and its effects on tomato plant growth, fruit yield,

and postharvest fruit quality. All experiments were arranged in a randomized complete

block design with four replications. Using drip irrigation, two experiments were

conducted in fall 2014 and spring 2016 at Myakka City, FL. Before planting, fluensulfone

was drip-injected at 2.0 and 2.8 kg a.i.·ha-1 after Pic-Clor 60 was shank-applied at 280

kg·ha-1. Using seepage irrigation, two experiments were conducted during the spring

and fall of 2016 at Immokalee, FL. Fluensulfone was incorporated before planting at 0,

2.0, and 4.0 kg a.i.·ha-1. HYDRUS 2D/3D software package was used to model

fluensulfone movement in the soil. In drip irrigation, at final harvest, Pic-Clor 60 followed

by either fluensulfone rate decreased RKN densities relative to Pic-Clor 60 alone by

more than 80% for both seasons. Similarly, Pic-Clor 60 followed by either fluensulfone

rate showed lower root galling rating. An increase of total marketable fruit yield was only

detected at the third harvest of the fall of 2014 (3265 RKNs·cm-3 soil), but fluensulfone

did not have an effect on yield in any harvest or tomato fruit size category in 2016 (800

RKNs·cm-3 soil). In seepage irrigation, HYDRUS 2D/3D simulation showed that

fluensulfone concentrated in the upper bed profile with residues below 2.0 mg·kg-1.

Fluensulfone treatments showed lower total plant and fruit dry weight (DW) at 90 days

after transplant (DAT) during the spring and lower fruit DW at 60 DAT during the fall.

However, fluensulfone treatments did not show phytotoxicity or decrease root, stem,

leaf DW, fruit yield, or impact postharvest fruit quality. Pic-Clor 60 followed by

fluensulfone was a viable tool for managing RKNs in drip-irrigated tomatoes in soils with

high RKN infestation, and the pre-plant incorporation of fluensulfone did not negatively

influence tomato production in seepage irrigation.

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CHAPTER 1 INTRODUCTION AND LITERATURE REVIEW

Introduction

Fresh-market vegetable production in the United States occupies approximately

62.7 million ha with a production value of US$11.9 billion in 2015 [U.S. Department of

Agriculture (USDA), 2016]. Tomatoes (Solanum lycopersicum L.), head lettuce (Lactuca

sativa), and romaine lettuce (Lactuca sativa L. var. longifolia) accounted for the highest

production value with a total worth of US$3.45 billion (USDA, 2016). In 2015, Florida

continued to rank first in fresh-market tomato production with 13,030 ha harvested

generating a production value of US$453 million (USDA, 2016). Florida tomato

production mainly occurs in the central and southern regions (Ozores-Hampton et al.,

2015) from November to January and April to May with well-defined growing seasons

extending from October to June (Ozores-Hampton et al., 2007). Florida fresh-market

tomatoes are normally grown on raised, polyethylene-mulched beds in sandy soils

having low water-holding capacity (Ozores-Hampton et al., 2015).

Common irrigation systems for Florida tomato production include seepage, drip,

and a combination of the aforementioned methods. Seepage, also known as subsurface

irrigation, has been regarded as the method most frequently used in Florida (Zotarelli et

al., 2013; Pitts et al., 2002). In seepage irrigation, water moves to the field via lateral

furrows from which water travels horizontally beneath the soil surface to form a perched

water table, and water consequently moves upward to the plant root zone by capillarity

(Smajstrla and Muñoz-Carpena, 2011). At planting, the water table is usually raised

near the top 46-cm (measured from the top of the bed); and throughout the growing

season, water table is maintained near the top 61-cm depth (Dukes et al., 2015).

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Furthermore, in seepage irrigation, soil moisture in the root zone is disproportionately

distributed across the field. In other words, plant rows closer to the water furrows tend to

be wetter than those rows located farther from the furrows (Zotarelli et al., 2013). To

provide sufficient moisture for plant growth in seepage irrigation, volumetric water

content should be maintained around the field soil capacity (between 12 and 18%)

(Zotarelli et al., 2013). Drip irrigation or micro-irrigation system, on the other hand,

consists of using an array of emitters, tubes, or tape to precisely and slowly apply water

to the root zone of the plant grown in plasticulture (Simonne et al., 2015). According to

Shukla et al. (2014), drip irrigation can be more water and fuel efficient achieving 90%

field application efficiency in comparison to seepage, which achieves between 20% and

50%. Towards water distribution improvement, drip and seepage have been combined

creating a seepage hybrid system (Zotarelli et al., 2013). Additionally, according to

Ozores-Hampton et al. (2010a), water furrows can be used alongside drip irrigation as a

measure for frost protection.

Despite being the number one producer of fresh-market tomato, Florida faces

many challenges. McAvoy and Ozores-Hampton (2014) have specified weather events

such as freezes, rainfall, and hurricanes; poor soils; labor; development and urban

sprawl; pest and diseases such as insects, weeds, and nematodes as the most

important factors affecting Florida growers. For instance, the root-knot nematodes

(RKNs), Meloidogyne spp., and sting nematodes, Belonolaimus longicaudatus are

among the most common and economically relevant nematode species affecting fresh-

market tomato production in Florida (Noling, 1999). Root-knot nematodes can be

considered as a main restraining factor for tomato production causing a serious

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decrease of yield and fruit quality (Noling, 1999). Root-knot nematodes have indeed

been regarded as the greatest nematode threat on tomato crop production in the world

(Noling, 1999). Plant injury due to RKNs infection involves the formation of “galls”

causing poor root function in water and nutrient uptake. Hence, plants exhibit slow

recovery to soil moisture adjustments showing wilting and stunting. Similarly, plants

present symptoms distinctive of nutrient deficiency such as chlorosis ultimately causing

yield reduction or losses. Furthermore, RKN-affected plants occur in patches across the

field due to the random distribution of RKN population densities (Duncan and Noling,

1998). Besides causing severe, direct crop damage, RKNs also interact with fungi and

bacteria creating plant disease complexes and contributing to yield declines and losses

(Mai and Abawi, 1987). A predisposition of tomato plants to Fusarium wilt (Fusarium

oxysporum) when infected with RKNs has been observed by Bowman and Bloom

(1966) and Sidhu and Webster (1978), who indicated that genetically resistant host

plant may turn into susceptible due to the presence of RKNs.

Until recent years, RKN management has relied heavily on the use of methyl

bromide (MeBr) as a broad-spectrum soil fumigant, effective not only against RKNs but

also against insects, weeds, and soilborne pathogens. However, after the phaseout of

MeBr [U.S. Environmental Protection Agency (EPA), 2000] and in conjunction with the

vast number of fumigant regulations, a need for soil applied non-fumigants to aid with

management of RKN is continuously increasing (Carpenter et al., 2000). Alternatives to

the banning of MeBr and the removal of other nematicides from the market do not leave

growers with highly effective management options (USDA, 2013). In 2011, a survey was

conducted among Florida tomato growers in regards to fumigation practices and

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challenges (Snodgrass et al., 2013). Growers’ responses represented 13,295 ha of the

total estimated 15,459 ha in Florida (86%). The survey indicated that growers were

experiencing production losses due to the lack of available alternatives (Snodgrass et

al., 2013). Current fumigants such as 1,3-dichloropropene, chloropicrin, and dimethyl

sulfide when properly applied offer broad spectrum activity and can aid RKN population

reduction (D. Dickson, personal communication). Nevertheless, application of these

fumigants represents higher costs to growers as well as required buffer zones and

application difficulties (Morris et al., 2015).

Fluensulfone, brand name NIMITZ, is a novel chemistry member of the

fluoroalkenyl thioester group developed to target RKNs on lowbush berries and cucurbit,

leafy, and fruiting vegetables (ADAMA Agricultural Solutions Ltd., Raleigh, NC) (Navia,

2014a). Fluensulfone is the first new chemical nematicide to be introduced in the market

for more than 20 years having the signal word of ‘Caution’, which involves no handling

restrictions and less complicated personal protective equipment requirements (Navia,

2014b). Fluensulfone then provides growers with no need for fumigant management

plans, restrictive buffer zones, and long re-entry intervals (Navia, 2014c). Furthermore,

upon application, pest mortality occurs within 24 to 48 hours (Navia, 2014b). In 2014,

fluensulfone received original registration from the EPA in accordance with the Federal

Insecticide, Fungicide, and Rodenticide Act (FIFRA) section 3(c)(5) and with registration

number 66222-243. In 2015, label registration was amended including section 24(c)

label for direct-seeded cucumber (Cucumis sativus), squash (Cucurbita spp.),

watermelon (Citrullus lanatus), cantaloupe (Cucumis melo), and okra (Abelmoschus

esculentu) in Florida counties (EPA, 2015). The dosage and method of application of

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fluensulfone is 2.0 to 4.0 kg a.i.·ha-1 applied via drip irrigation, banded incorporated, or

broadcast incorporated. Two to five days after application, 1.27 to 2.54 cm of water

needs to be applied to avoid seedling exposure to elevated product residues (maximum

residual concentration ~1.0 mg·kg-1) and to achieve negligible phytotoxicity (E. Segal,

personal communication). Previous studies have demonstrated promising results

proving suitable management of RKNs in vegetable crops (Dickson and Mendes, 2013;

Morris, 2015; Oka et al., 2009; Oka et al., 2013; Rubin et al., 2011). However, limited

information was found in the literature regarding fluensulfone efficacy in sandy soils in

Florida. Furthermore, the distribution of the nematicide in the soil in seepage irrigation is

unknown.

Hypothesis

Pre-plant application of fluensulfone will provide optimum management of RKNs

in drip irrigation; however, fluensulfone will concentrate in the upper soil profile causing

severe phytotoxicity because of the upward movement of water in seepage irrigation.

Objectives

1. To evaluate the effect of shank-applied Pic-Clor 60 followed by drip-applied

fluensulfone on fresh-market tomato plant vigor, RKN soil population density, root

galling index, and fruit yield during the fall 2014 and spring 2016 seasons,

2. To study the soil distribution and movement of pre-plant incorporated

fluensulfone and to evaluate its effects on fresh-market tomato plant growth, fruit yield,

and postharvest quality using seepage irrigation during the spring and fall 2016

seasons.

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Literature Review

Root-Knot Nematodes: Disease Cycle of a Global Plant Pathogen

Nematodes belong to the phylum Nematoda and can be defined as ubiquitous

pseudocoelomates with unsegmented bodies found in fresh and salt water, soil, and as

internal parasites of living organisms such as animals and humans (Blaxter, 2011). Until

recently, over 25,000 nematode species have been identified (Zhang, 2013), from which

10,000 have been described as parasites (Maggenti, 1981). Among plant-parasitic

nematodes, RKNs have been included in the group of the most severe plant pathogens

affecting all types of crops worldwide (USDA, 2013). Nearly 100 species of the

Meloidogyne genus have been identified; however, five major species have been

labeled as “major plant-parasitic nematodes of economic importance” (Handoo, 1998).

These species are M. arenaria, M. incognita, M. javanica, M. hapla, and M. chitwoodi

(Handoo, 1998). Root-knot nematodes are assumed to cause annual crop losses of

approximately US$10 billion in the United States of America and US$125 billion globally

(Chitwood, 2003; Sasser and Freckman, 1987). In Florida, M. javanica, M. arenaria, M.

incognita, M. enterolobii, and M. floridensis are considered the most important species

(D. Dickson, personal communication). Root-knot nematodes have a life cycle that

includes egg stage, four juvenile stages, four molts, and one adult stage and are

considered as sedentary endoparasites. According to Tyler (1933), a mature female that

establishes a specialized feeding site within plant roots will lay between 500 and 1,000

eggs during her life time. The eggs undergo embryogenesis with a first-stage juvenile

developed within each egg. The juvenile undergoes the first molt within the egg shell,

and breaks free of the shell moving into the surrounding soil. After hatching, RKNs are

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categorized as infectious second-stage juveniles (J2). Root-knot nematodes will infect

plant root tips, penetrating in the area of cell elongation of root growing points and will

migrate within the roots, wandering around until the movement becomes more

purposeful (D. Dickson, personal communication). Root-knot nematodes, with their

head oriented towards the region of the plant vascular system, begin to initiate feeding

by secreting proteins from the esophageal glands, transforming parasitized cells into

hypertrophic cells, also known as “giant cells” (Bird, 1961). The surrounding cortex cell

will become hyperplastic thereby rapidly increasing in numbers to induce gall formation.

Hypertrophic cells act as nutrient reservoirs for females. With large numbers of females

feeding from inside the roots, resulting in nutrient losses and water uptake malfunction,

thereby stressing the plant and causing aboveground symptoms such as chlorosis,

stunting, and incipient wilting of the leaves (Karssen et al., 2013).

Alternatives for Root-Knot Nematode Management in Vegetable Production

Current alternatives for RKN management may be divided into two categories:

cultural practices and chemical management.

Cultural practices

These practices include crop rotation, resistant cultivars, fallowing, and flooding.

For crop rotation to be successful, incompatible crops for RKN infection need to be

included. For instance, Noling (2016) has listed cover crops such as clay cowpea (Vigna

unguiculata), sunn hemp (Crotalaria juncea), and American jointvetch (Aeschynomene

americana) as poor host legumes that may be included in double cropping for RKN

management. Alternatively, the use of RKN resistant cultivars in tomato relies on one

single dominant gene known as the Mi gene (Medina-Filho and Tanksley, 1983; Smith,

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1944; Williamson et al., 1994). Some studies have documented, however, gene

instability due to high temperatures causing resistance failure (Dropkin, 1969; Hwang et

al., 2000). Fallowing refers to land left uncultivated for a determined period of time to

induce starvation in RKNs; hence, fallowing may oftentimes be considered one of the

most effective cultural approaches (Noling, 2016). Nonetheless, Krueger and McSorley

(2014) explained that when fallowing is used, RKN may tend to enter into a less active

stage which benefits them to survive extended periods of time without food. However,

fallowing may be regarded as a poor practice to enhance soil conservation and nutrient

drainage (Krueger and McSorley, 2014). Flooding could be employed as a means to

suppress RKN population densities. By alternating flooding and drying cycles, RKNs

undergo abiotic stress resulting in population decline (Noling and Becker, 1994).

Nevertheless, the growing concern of water use efficiency and aquifer exhaustion has

triggered a reduction on the use of flooding (Noling, 2016).

Chemical management

Nematicides can be defined as chemicals that either kill or immobilize

nematodes. Current nematicides may be grouped into two different categories based on

their movement in the soil: fumigants and non-fumigants (Table 1-1) (Noling, 2014).

Generally, fumigant nematicides are liquid formulations that rapidly volatize once

introduced into soil. These groups may be divided into halogenated hydrocarbons and

those that release carbon disulfide or methyl isothiocyanate (Nyczepir and Thomas,

2009; Morris, 2015). Methyl bromide (Terr-O-Gas 98, Great Lakes Corp., Middlebury,

CT), chloropicrin (Chloropicrin 100, Cardinal, Hollister, CA) and 1,3-dichloropene

(Telone II, Dow Agrosciences LLC, Indianapolis, IN) are considered halogenated

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hydrocarbons whereas metam sodium (Vapam, AMVAC Chemical Cop., New Port

Beach, CA) or metam potassium (Kpam, AMVAC Chemical Cop., New Port Beach, CA)

releases methyl isothiocyanate in the soil (Nyczepir and Thomas, 2009; Morris, 2015).

Non-fumigants are mostly formulated as granules or liquids and move in soil or water by

downward percolation and can be either carbamates or organophosphates acting as

nematistats by inhibiting acetylcholinesterase activity (Haydock et al., 2006; Morris,

2015; Opperman and Chang, 1990).

In Florida, current fumigants that may be applied to manage RKN in tomato

include chloropicrin, metam sodium, metam potassium, 1,3-dichloropropene, dimethyl

disulfide (Paladin, Arkema Inc., King of Prussia, PA), and allyl isothiocyanate (Dominus,

Isagro USA Inc., Morrisville, NC) (Dittmar et al., 2016). In 2011, Florida tomato growers

identified metam sodium, metam potassium, and chloropicrin as the less effective in

managing RKN (Snodgrass et al., 2013), whereas the remaining fumigants are known

to provide an acceptable level of management of RKN (Dittmar et al., 2016). In spite of

the favorable RKN management that fumigants may offer, Florida tomato growers

indicated that the use of fumigants involves a high cost, and that product availability is

not always certain (Snodgrass et al., 2013). Furthermore, soil non-selective fumigants

commonly used in Florida increase the potential of pesticide drift and the negative

effects of off-target contamination (Fishel and Ferrel, 2010). Oxamyl is the only non-

fumigant nematicide labeled for management of RKN on tomato in Florida that can be

applied during the crop cycle (Noling, 2016). Oxamyl is a liquid formulation with

downward and upward moving systemic activity, which can be foliar or ground applied,

as a soil drench, broadcast, or through chemigation. Growers may use oxamyl as a

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post-plant supplement throughout the tomato growing season in combination with

fumigant nematicides since it acts a nematistat temporally paralyzing RKNs (Noling,

2016; Morris et al., 2015).

Fluensulfone, a Recent Introduction of New Chemistry for Management of Root-Knot Nematodes

Fluensulfone [5-chloro-2 (3,4,4-trifluoro-but-3-ene-1-sulfonyl)-thiazole], (Nimitz,

ADAMA Agricultural Solutions Ltd., Raleigh, NC), is a non-fumigant nematicide

formulated as an emulsifiable concentrate with 480 g a.i.·L-1. Fluensulfone has shown

relatively low toxicity to non-target insects and other animals (Kearn et al., 2014; Oka et

al., 2009; Oka et al., 2013). In contrast to carbamates and organophosphates,

fluensulfone does not act by nematode paralysis via inhibition of acetylcholinesterase

activity (Kearn et al., 2014; Oka et al., 2009; Oka et al., 2013). Previous studies have

shown that fluensulfone has nematicidal activity as well as systemic activity in the plant

to manage RKNs (Kearn et al., 2014; Oka et al., 2009; Oka et al., 2011). Rubin et al.

(2011) reported that when fluensulfone was applied through drip irrigation, product

migration occurred to deeper layers (~30 cm) in heavy clay soil. Furthermore,

fluensulfone was found to undergo a concentration decline throughout time rapidly

dissipating from the soil within 10 days after application, but still providing satisfactory

RKN management (Rubin et al., 2011). However, in seepage irrigation water movement

may be upward due to capillarity action and; as a result, fluensulfone may potentially

concentrate in the upper section of bed profile causing acute phytotocixity (E. Segal,

personal communication).

23

Modeling Pre-Plant-Incorporated Fluensulfone with HYDRUS 2D/3D Using Seepage Irrigation

HYDRUS two- and three-dimensional (2D/3D) software package (PC-Progress,

Prague, Czech Republic) is a numerical model developed to analyze and simulate water

flow, heat, and solute transport in saturated, unsaturated, or partially saturated porous

media (Šimůnek et al., 2006; Šejna and Šimůnek, 2007). HYDRUS 2D/3D was initially

designed as a two-dimensional model and updated from HYDRUS 1D (Šimůnek et al.,

1998; 2005). This mathematical model solves the Richards equation for saturated-

unsaturated water flow (Richards, 1931), the convection-dispersion equations for heat

and solute transport, and the diffusion equation for solute movement in the gaseous

phase. Solute particle movement in a porous medium can be explained by advection,

diffusion, and/or mechanical dispersion. Advection refers to how the bulk motion of the

fluid carries the solute particles, diffusion explains how the random molecular motion of

the solute particles themselves cause them to spread, and mechanical dispersion refers

to the spreading of the solute particles caused by varying velocities in the pores of the

medium (Logan, 2001). Therefore, HYDRUS 2D/3D may be used to study and simulate

how fluensulfone particles may be carried by the bulk motion of the fluid and possibly

explain the concentration gradients in sandy soils, and the effect on fluensulfone of the

upward movement of water in seepage irrigation.

The Richards equation:

𝜕𝜃

𝜕𝑡=

𝜕

𝜕𝑧 [𝐾(𝜃) (

𝜕ℎ

𝜕𝑧+ 1)]

Equation (1-1)

24

Equation 1-1 includes K is the hydraulic conductivity, h is the matric head

induced by capillary action, z is the elevation above a vertical datum 𝜃 is the volumetric

water content, and t is time (Richards, 1931).

The convection-dispersion equation:

𝜕𝑐

𝜕𝑡= ∇ ∙ (D∇c) − ∇ ∙ (𝑣𝑐) + 𝑅

Equation (1-2)

Equation 1-2 includes the variable of interest (c), tendency to diffuse (D), average

velocity (v), "sources" or "sinks" of the quantity c (R), and the gradient (∇) (Logan,

2001).

The diffusion equation:

𝜕∅(𝑟, 𝑡)

𝜕𝑡= ∇ ∙ [𝐷(∅, 𝑟) ∇∅(𝑟, 𝑡)]

Equation (1-3)

Equation 1-3 for diffusion includes the density of diffusing material (∅), the

location and time of diffusing material (r and t), the vector differential operator (∇), and

the collective diffusion coefficient [D (ϕ, r) ] (Logan, 2001).

25

Table 1-1. Current fumigant and non-fumigant nematicides available in Florida to manage plant-parasitic nematodes on vegetables.

Nematicide category

Brand name Active ingredient Rate·ha-1

Fumigant Chloropicrin Chloropicrin 112 – 392 kg Dominus Allyl isothiocyanate 94 – 374 L

Kpam Potassium N methyldithiocarbamate 281 – 580 L Paladin Dimethyl disulfide 507– 561 L

Pic-Clor 60 1,3-Dichloropropene/ chloropicrin 40/60 (w/w) 182 – 323 L Telone II 1,3-Dichloropropene 84 – 112 L

Telone C17 1,3-Dichloropropene/ chloropicrin 81/17 (w/w) 101 – 160 L Telone C35 1,3-Dichloropropene/ chloropicrin 63/35 (w/w) 122 – 192 L

Vapam Metam sodium 551 – 702 L

Non-fumigant Nimitz Fluensulfone 4 – 6 L Vydate L Oxamyl 2 – 5 L

Adapted from Dittmar et al., 2016; Noling, 2014.

26

CHAPTER 2

EFFECTS OF FLUENSULFONE AND SOIL FUMIGATION ON ROOT-KNOT NEMATODES AND FRUIT YIELD OF DRIP-IRRIGATED FRESH-MARKET TOMATO

Introduction

Florida continues to be the leading fresh-market tomato (Solanum lycopersicum

L.) state, generating a production value of US$453 million and an average yield of 37.2

Mg·ha-1 [United States Department of Agriculture (USDA), 2016]. Nationally, Florida

fresh-market tomato harvested area and production value accounted for 34% and 36%,

respectively (USDA, 2016). Production of tomato mainly occurs in the central and

southern regions of the state (Ozores-Hampton et al., 2015) extending from November

to June (Ozores-Hampton et al., 2007). Tomato is typically grown on raised,

polyethylene-mulched beds in sandy soils that have low water-holding capacity

(Ozores-Hampton et al., 2015). Polyethylene mulch systems may utilize drip irrigation to

allow for controlled application of water, fertilizer, and pesticides (Simonne et al., 2015).

The adoption of drip irrigation has increased rapidly for the past decades. In 1970, an

estimated 50,000 ha were using drip irrigation nationwide (Apt and Caswell, 1988). By

2008, approximately 1.52 million ha were under drip irrigation (USDA, 2008). Drip

irrigation achieves 90% field application efficiency in terms of water and fuel (Shukla et

al. 2014).

Although Florida ranks high in fresh-market tomato production, there remain

many challenges. Root-knot nematodes (RKNs), Meloidogyne spp., have been included

in the group of the most damaging soilborne plant pathogens affecting tomato (USDA,

2013). In tomato production, RKNs represent a limiting factor that can have adverse

effects on fruit yield and quality (Duncan and Noling, 1998). Plant injury due to RKN

27

infection involves the formation of galls that cause poor root uptake of water and

nutrients (Duncan and Noling, 1998). Hence, plants may exhibit moisture and nutrient

deficiency symptoms such as incipient wilting, stunting, yellowing of the leaves, and

ultimately crop yield reduction under conditions well tolerated by healthy plants (Duncan

and Noling, 1998). Symptoms of RKNs occur in patches across the field due to the

cluster distribution of RKN population densities (Duncan and Noling, 1998). Sandy soils

play a fundamental role in RKN movement, reproduction, and survival. Taylor and

Sasser (1978) indicate that RKN infestation is more severe in sandy soils than in clay

soils. Drip irrigation can be used in sandy soils to deliver nematicides directly to the

plant root zone either before planting to manage RKNs or after planting to rescue

infested crops (Noling, 2005).

Beginning in 1961, Florida tomato growers relied on methyl bromide (MeBr) as a

broad-spectrum soil fumigant against soilborne diseases, weeds, and nematodes

(Gilreath et al., 1994). However, after the complete phaseout of MeBr in 2005 under the

Montreal protocol [U.S. Environmental Protection Agency (EPA), 2000], tomato growers

were seeking an alternative with similar benefits that mebr provided (Noling, 2016). Pic-

Clor 60 [1,3-dichloropropene plus chloropicrin (40:60, w/w)] (Agrian, Inc., Fresno, CA)

was identified as one of the main alternative fumigants to MeBr in a survey conducted

among Florida tomato growers in 2011 (Snodgrass et al., 2013). Growers indicated that

pest-pathogen problems were increasing, and that production losses were experienced

due to the unsatisfactory efficacy of available alternatives (Snodgrass et al., 2013).

Preliminary research has shown that currently available pre-plant chemical soil

fumigants alone may not offer optimal RKN management (Di Gioia et al., 2016). In

28

addition, recent studies have shown that current fumigant alternatives to MeBr with low

vapor pressures and high boiling points that do not distribute vertically in the soil profile

and thus allow nematode survival in deeper layers (Noling, 2016; Noling et al., 2016).

Alternatively, oxamyl (Vydate, DuPont Crop Protection, Hayward, CA), a non-fumigant

nematistat that paralyzes nematodes, is commonly applied in post-planting (Wright,

1981; Rich et al., 2004). Post-plant applications of oxamyl have not shown to provide

plant growth and yield recovery since, once RKN infection takes place and plant

damage occurs, crop rescue becomes dependent on frequency of product application

and the time of RKN detection. Oxamyl is one of the two non-fumigant nematicides that

have been used for RKN management in tomato culture in Florida (Noling, 2016).

Currently, production of oxamyl has been halted due to a factory incident involving a

toxic chemical release [U.S. Chemical Safety Board (CSB), 2016].

Fluensulfone [5-chloro-2 (3,4,4-trifluoro-but-3-ene-1-sulfonyl)-thiazole], (Nimitz,

ADAMA Agricultural Solutions Ltd., Raleigh, NC), is a novel chemistry of the

fluoroalkenyl thioester group developed to target RKNs on lowbush berries and cucurbit,

leafy, and fruiting vegetables (Navia, 2014a). The dosage and method of application of

fluensulfone is 2.0 to 4.0 kg a.i.·ha-1 applied via drip irrigation, banded incorporated, or

broadcast incorporated (Navia, 2014a). Fluensulfone is a recent introduction of new

chemistry for management of nematodes having the signal word of ‘Caution’ (Navia,

2014b). In contrast to carbamates and organophosphates, fluensulfone does not act by

nematode paralysis via inhibition of acetylcholinesterase activity (Kearn et al., 2014;

Oka et al., 2009; Oka et al., 2013). Previous studies have shown that fluensulfone has

29

nematicidal activity as well as systemic activity in the plant (Kearn et al., 2014; Oka et

al., 2009; Oka et al., 2011).

Since 2008 preliminary studies on carrot (Daucus carota subsp. sativus),

cucumber (Cucumis sativus L.), eggplant (Solanum melongena), squash (Cucurbita

spp.), potato (Solanum tuberosum L.), sweet potato (Ipomoea batatas), lettuce (Lactuca

sativa), and tomato have shown that application of fluensulfone reduced RKN galling on

plant roots and soil population densities of juveniles compared with a non-treated

control (Dickson and Mendes, 2013; Rubin et al., 2011). In a tomato-cucumber double

cropping system, fluensulfone reduced root galling index by 73% in the tomato crop with

RKN suppression persisting into the second crop (Morris et al., 2015). Snodgrass et al.,

2013 and Di Gioia et al., 2016 showed that RKN management with Pic-Clor 60 still

remains a challenge. The effectiveness of Pic-Clor 60 to manage RKNs could be

enhanced with the use of fluensulfone. The objective of this study was to evaluate the

effect of shank-applied Pic-Clor 60 followed by drip-applied fluensulfone on fresh-

market tomato plant vigor, RKN soil population density, root galling index, and fruit yield.

Materials and Methods

Field Preparation and Treatment Application

During the fall 2014 and spring 2016 seasons, two experiments were conducted

in commercial fresh-market tomato fields with histories of high RKN soil infestations

located at Myakka City, FL. The soil type was a Myakka fine sand (sandy, siliceous,

hyperthermic Aeric Haplaquods) (Natural Resources Conservation Service, 2016). Soil

sand, silt, and clay contents were 98.0, 1.0, and 1.0%, respectively; and soil pH was

5.3. On 5 Aug. 2014 and 21 Dec. 2015, prior to bedding, a starter fertilizer mix of

30

nitrogen (N) and potassium (K) was broadcasted and incorporated at rates of 22 and

212 kg·ha-1 [sources: ammonium nitrate (NH4NO3) and potassium sulfate (K2SO4)],

respectively. Then, 12-m-long and 20-cm-tall, raised beds were formed on 1.83-m

centers using a 91-cm-wide bed shaper. Subsequently, beds were fumigated with Pic-

Clor 60 at 280 kg·ha-1, shank-applied with three chisels per bed, each spaced 15 cm

apart, and placed 20-cm deep. Immediately after fumigation, beds were covered with

virtually impermeable film, white-on-black and black-on-black in 2014 and 2016,

respectively (Berry Plastics, Evansville, IN). A single 8-mm drip tape with 32-cm

emitters spacing and a flow rate of 0.98 L·h-1 was placed off center at 20 cm from bed

shoulder and 5 cm deep from bed top (Model Jain Turbo Cascade 11653050; Jain

Irrigation, Inc., Jalgaon, India). Three weeks after fumigation, on 2 Sept. 2014 and 11

Jan. 2016, fluensulfone treatments were injected into plots arranged in a randomized

complete block design with four replications. Treatments were injected into the drip tape

at two different rates: 2.0 and 2.8 kg a.i·ha-1 using a spot sprayer with an open flow of

498 L·h-1 (Model GRN-7822-201; Countyline Tractor Supply Co., LaBelle, FL). Pic-Clor

60 alone represented the control and reference grower standard treatment. In each plot,

the drip tape was cut at the end and closed using end caps (DripWorks, Inc., Willits, CA)

to prevent cross-contamination among treatments. For treatment injection, 10 m3·ha-1 of

water were first applied, followed with 47 m3·ha-1 of water for fluensulfone application,

and 6 m3·ha-1 of water to flush residues and clear the drip tape. After treatment

application, the drip tapes were re-connected using couplers (DripWorks, Inc., Willits,

CA) to allow for continuous irrigation across experimental plots. On 6 Sept. 2014 and 16

Jan. 2016 [4 and 5 days after application (DAA)], the crop was irrigated with 7 m3·ha–1

31

water. On 12 Sept. 2014 (10 DAA) and 20 Jan. 2016 (9 DAA), 6-week-old seedlings of

large, round, determinate, fresh-market tomato cv. ‘HM 1823’ (HM.CLAUSE, Inc., Davis,

CA) grown in 128-cell styrofoam trays (Mobley Plant World, LaBelle, FL), were

transplanted 61 cm apart in a single row for each bed establishing 20 plants per plot

and a population of 8,970 plants·ha-1. ‘HM 1823’ is an early season tomato with 70-74

days to maturity, which required tying and staking and had no resistance to RKNs.

Fertigation was used to supplement the pre-plant fertilizer with 48–3–40 kg·ha-1 N–P–K

on a weekly basis. Both trials were irrigated using drip irrigation. Irrigation run times

were 57 min·ha-1 for 6 days per week with a flow rate of 0.30 m3·ha-1·min-1 for a total

water discharge of 17 m3·ha-1·day-1. Pest management tactics were applied based on

weekly scouting reports and UF/IFAS recommendations (Santos et al., 2013).

Data Collection

Average minimum, mean, maximum daily air and soil temperatures, and total

rainfall accumulation were recorded by the Florida Automated Weather Network

(FAWN) for Balm, FL. Prior to treatment application, at midseason, and at final harvest,

six soil cores per plot were randomly collected at 20 cm deep using a soil probe for

sandy soils (Oakfield Apparatus, Inc., Oakfield, WI). Soil cores from each plot were

mixed thoroughly to create one composite sample of 250 cm3 of soil. Samples were

placed in a cooler for preservation. Soil samples were then sent to LLH Ag and

Research Services, LLC, Tifton, GA for nematode quantification and identification. The

levels of soil population densities of RKN second-stage juveniles (J2) were categorized

as low, medium, or high according to Barker et al., 1976. A representative harvest unit

(RHU) of 10 plants was marked at the center of each plot. At midseason, on 31 Oct.

32

2014 and 8 Mar. 2016 [49 and 48 days after planting (DAP)], and final harvest, on 23

Dec. 2014 (102 DAP) and 10 May 2016 (111 DAP), three plants at the edges of the

RHU and six plants within RHU were selected for RKN root galling evaluation,

respectively. Root-knot nematode root galling index was visually assessed according to

Hussey and Janssen (2002) rating system using a 0 to 5 continuous scale, where zero

= no traces of root galling, 1 = infection with few small galls, 2 = less than 25% of roots

galled, 3 = between 25 to 50%, 4 = between 51 and 74%, and 5 = greater than 75 % of

roots galled. Plant vigor was visually assessed at 25 and 20 DAP in the fall of 2014 and

spring of 2016, respectively, based on a 1-10 continuous rating scale, where 1 = poor

overall plant growth and 10 = optimal uniform plant growth. Tomato fruit within RHU

were manually harvested and weighed three times at mature-green stage at 73, 88, and

102 DAP in 2014 and at 92, 103, and 111 DAP in 2016. Fruit yield was classified into

marketable and unmarketable. Marketable fruit yield was graded according to USDA

size category specifications—extra-large (diameter > 7.00 cm), large (6.35 to 7.00 cm),

and medium (5.72 to 6.43 cm) (USDA, 1997). Tomato fruit were considered

unmarketable based upon size less than 5.72 cm and the presence of defects such as

sunscald, scratch, off-shape, catfaced, and graywall (Jones et al., 1991; Ozores-

Hampton et al., 2010).

Statistical Analysis

Plant vigor, RKN soil population density, root galling index, and fruit yield were

subjected to analysis of variance (ANOVA) using the GLM procedure and means were

separated according to Duncan’s multiple range test at 5% confidence level using SAS

(SAS 9.3, SAS Institute Inc., Cary, NC, 2012). Root-knot nematode densities were

33

transformed by square-root transformation prior to analysis to obtain a normal

distribution.

Results

Weather Conditions

Average minimum, maximum, and mean air and soil temperatures were within

the range of average temperatures recorded in the previous 10 years for both fall 2014

and spring 2016 seasons (Table 2-1). There were no freezing events reported during

both seasons. Total rainfall accumulation for fall 2014 and spring 2016 were 276.1 and

104.9 mm greater than the previous 10-year average (Table 2-1).

Plant Vigor, Root-Knot Nematode Soil Density, and Root Galling

Application of fluensulfone to fumigated soil (Pic-Clor 60) did not affect plant

vigor in 2014 and 2016. Tomato plants exhibited optimal uniform growth with all

treatments during both years (Table 2-2). Initial population densities of RKN J2 before

treatments were applied were low in 2014 and 2016 (10/100 and 30/100 cm3 of soil,

respectively). In 2014, at final harvest, Pic-Clor 60 followed by 2.0 and 2.8 kg a.i·ha-1

fluensulfone decreased population densities of RKN J2 as compared to Pic-Clor 60

alone by approximately 96 and 81%, respectively (P ≤ 0.001). Similarly, in 2016, at final

harvest, Pic-Clor 60 followed by 2.0 and 2.8 kg a.i·ha-1 fluensulfone decreased

population densities as compared to Pic-Clor 60 alone by approximately 85 and 94%,

respectively (P < 0.05). However, there were no significant differences among

fluensulfone rates at midseason and final harvest for both years [P > 0.05 (Table 2-2)].

In 2014 and 2016, at final harvest, combining fluensulfone at 2.0 kg a.i·ha-1 with Pic-

Clor 60 reduced root galling index as compared to Pic-Clor 60 alone by 57 and 90%,

34

respectively (P = 0.0001). There were no significant differences among fluensulfone

rates in either year.

Tomato Fruit Yield and Grade Distribution

In 2014, neither Pic-Clor 60 alone nor Pic-Clor 60 followed by fluensulfone had

an effect on any tomato fruit size categories or total marketable and nonmarketable

yield at first and second harvest, separately [P > 0.05 (Table 2-3)]. However, when first

and second harvests were combined, differences among treatments were only found in

the extra-large fruit size category (data not shown). Pic-Clor 60 alone and Pic-Clor 60

followed by fluensulfone at 2.8 kg a.i·ha-1 accounted for the greatest extra-large fruit

yield (P = 0.04) (data not shown).

At the third harvest in 2014, both 2.0 and 2.8 kg a.i·ha-1 fluensulfone produced

highest fruit yield for all tomato size categories and total marketable yield [P < 0.05

(Table 2-3)], except for the unmarketable yield where no differences were found among

treatments (P > 0.05) (data not shown). Pic-Clor 60 alone and Pic-Clor 60 followed by

fluensulfone at 2.8 kg a.i·ha-1 accounted for the greatest total season extra-large fruit

yield (P = 0.05). There were no differences for the remaining tomato size categories and

for the total season marketable and unmarketable yields in 2014 (P > 0.05). In 2016,

inclusion of fluensulfone at 2.0 and 2.8 kg a.i·ha-1 in the fumigated soil did not have a

significant effect on yield in any harvest or tomato fruit size category [P > 0.05 (Table 2-

3)].

Discussion

This study demonstrated that fluensulfone in combination with Pic-Clor 60 can be

an effective tool to manage RKNs in drip-irrigated fresh-market tomato grown in sandy

35

soils with high RKN infestation. In the fall of 2014 when RKN infestation was high, the

weather conditions may have contributed in facilitating RKN reproduction and survival

(Table 2-1). Optimum air and soil temperatures for M. hapla and related species range

from 15 to 25 °C and 15 to 20 °C, respectively; and corresponding temperatures for M.

javanica and related species range about 5 °C higher (Taylor and Sasser, 1978;

Wallace, 1964). The cumulative fall season rainfall was 276.1 mm higher than the

previous 10-year average, which offered nematodes ideal conditions to complete their

life cycles since high moisture content enhances nematode movement (Djian-

Caporalino et al., 2009) and egg hatching (Van Gundy, 1985). In the spring of 2016

when RKN infestation was low, the cool air and soil temperatures at the beginning of the

growing season (e.g. 0.9 and 13.6 °C on 25 Jan. 2016, respectively) may have played a

role in increasing the duration of the RKN life cycle and decreasing reproduction and

hatching (Collange et al., 2011).

During the fall of 2014 and the spring of 2016, injection of fluensulfone through

the drip tape after soil fumigation with Pic-Clor 60 did not affect plant vigor observed at

25 and 20 DAT, respectively. Similarly, in a tomato-cucumber double-cropping system,

application of fluensulfone did not affect tomato plant vigor; nonetheless, fluensulfone

improved cucumber plant vigor as compared to a non-treated control as well as reduced

root galling (Morris et al., 2015).

Although initial RKN population densities before treatment application were low

for both seasons, the effect of fluensulfone was observed when RKN population

densities reached higher levels throughout the season, especially at the third harvest.

Both fluensulfone rates reduced RKN populations and root galling during the fall of 2014

36

and the spring of 2016. However, the level of suppression was greater in the fall of 2014

when RKN infestation was high, which may be explained by the fact that nematode

damage and dynamics are population density dependent (Seinhorst, 1965). In the fall of

2014, inclusion of drip-injected fluensulfone to the nematode management program

provided a more effective level of RKN control compared to Pic-Clor 60 alone. In the

presence of high RKN infestation, the combination of fluensulfone and Pic-Clor 60

improved tomato yield at the third harvest. In contrast during the spring of 2016, tomato

yield did not reflect the effect of the nematicide due to the low RKN infestation. These

findings are consistent with the results of Morris et al. (2015) who showed that tomato

yield did not respond to fluensulfone in fields with low RKN infestation. Norshie et al.

(2016) indicated that fluensulfone treatments reduced potato cyst nematode (Globodera

pallida) root infection by 43% and increased yield by 61.5% at greater root infection

(1125.8 RKN J2·g-1 root) whereas potato yield did not respond when there was lower

infection (444.2 RKN J2·g-1 root).

Summary

In 2014 and 2016, at final harvest, Pic-Clor 60 followed by 2.0 and 2.8 kg a.i·ha-1

fluensulfone decreased population densities of RKN J2 as compared to Pic-Clor 60

alone by 96 and 81% and 85 and 94%, respectively. Combining fluensulfone at 2.0 kg

a.i·ha-1 with Pic-Clor 60 reduced root galling index as compared to Pic-Clor 60 alone by

57 and 90% at final harvest in 2014 and 2016, respectively. However, an increase of

total marketable fruit yield was only observed at the third harvest of the fall of 2014

when there was a high level of RKN infestation (3265 RKNs·cm-3 soil). Inclusion of

fluensulfone at 2.0 and 2.8 kg a.i·ha-1 after Pic-Clor 60 did not have an effect on yield in

37

any harvest or tomato fruit size category when RKN infestation was low in 2016 (800

RKNs·cm-3). Further research is needed to support the results presented in this study,

particularly considering other integrated management practices, commercial crops, and

different soil types.

38

Table 2-1. Summary of minimum (Min.), mean, and maximum (Max.) daily average air and soil temperatures and total rainfall accumulation during the fall of 2014, the spring of 2016, and 10-year fall and spring averages for Myakka City, FL.

Period

Temperature (°C) Total

rainfall Air Soil (-10 cm depth)

Min. Mean Max. Min. Mean Max. (mm)

Fall 2014 Septembera 21.1 24.7 30.9 25.4 26.3 27.2 228.9 October 16.4 22.4 29.2 23.5 24.3 25.2 54.9 November 10.9 16.8 23.7 18.8 19.6 20.4 182.9 December 10.5 16.1 23.0 16.8 17.6 18.4 4.1 Average/total 14.7 20.0 26.7 21.1 21.9 22.8 470.7 Fall 10-year average 15.4 20.9 27.6 23.0 23.7 24.5 194.6 Spring 2016 January 7.9 13.7 20.0 15.5 16.1 16.9 66.5 February 9.1 15.5 22.3 16.4 17.2 18.2 42.4 March 14.7 20.5 27.3 19.7 20.6 21.6 49.3 April 15.5 21.9 28.6 22.1 23.2 24.3 56.6 May 15.5 22.2 28.7 22.6 23.8 25.2 84.1 Average/total 12.6 18.8 25.4 19.3 20.2 21.2 299.0 Spring 10-year average 11.9 18.9 26.2 19.6 20.7 21.8 194.1

a The temperature averages and rainfall totals were recorded daily from 12 Sept. through 23 Dec. 2014 and from 20 Jan. through 10 May 2016. Data source: Florida Automated Weather Network station located in Balm, FL, at 64.4 km of distance from the field (http://fawn.ifas.ufl.edu/).

39

Table 2-2. Effect of pre-plant drip-injected fluensulfone on plant vigor, root-knot nematode [Meloidogyne spp. (RKN)] soil population density, and root galling index in tomato grown during the fall of 2014 and the spring of 2016 in Myakka City, FL.

Treatment

Plant vigor

(rating 1-10)a

RKNs·100 cm-3 soilc

Root galling index (rating 1-5)b

Fall 2014 (DATd)

25 49 102 49 102

Pic-Clor 60e 10f 7.5 3265.0a 1.9a 4.4a Pic-Clor 60+fluensulfone 2.0 kg a.i·ha-1 10 5.0 120.0b 0.7b 1.9b Pic-Clor 60+fluensulfone 2.8 kg a.i·ha-1 10 5.0 632.5b 0.8b 2.1b P-value - 0.96 0.001 0.0001 0.0001 Significance - NS *** *** *** Spring 2016 (DAT) 20 48 111 48 111 Pic-Clor 60 10 11.7 800.0a 0.3a 1.1a Pic-Clor 60+fluensulfone 2.0 kg a.i·ha-1 10 20.0 120.0b 0.0b 0.1b Pic-Clor 60+fluensulfone 2.8 kg a.i·ha-1 10 26.7 47.5b 0.0b 0.0b P-value - 0.50 0.03 0.03 0.0001 Significance - NS * * ***

a Plant vigor was visually assessed based on a 1-10 scale, where 1 = poor overall plant growth and 10 = optimal uniform plant growth. b 0 = no root galling, 1 = trace infection with a few small root galls, 2 ≤ 25% root galls, 3 = 25-50%, 4 = 51-74%, and 5 ≥ 75 % of root galls (Hussey and Janssen, 2002). c Second-stage juveniles (J2) count data were transformed using the square-root function before statistical analysis. d DAT = days after transplanting e Pic-Clor 60 = 1,3-dichloropropene plus chloropicrin (40:60, w/w) at 280 kg·ha-1. f Within season means followed by different letters are significantly different according to Duncan’s multiple range test at 5%. NS *, **, *** Nonsignificant or significant at P ≤ 0.05, 0.01, or 0.001, respectively.

40

Table 2-3. First, second, third, and total season marketable and unmarketable tomato fruit yield by size categories in response to pre-plant drip-injected fluensulfone during the fall of 2014 and the spring of 2016 in Myakka City, FL.

a XL = extra-large (greater than 7.00 cm); L = large (6.35 to 7.00 cm); M = medium (5.72 to 6.43 cm); ); TM = total marketable, UM = unmarketable [fruit with defects such as sunscald, scratch, off-shape, catfaced, and graywall (Jones et al., 1991; Ozores-Hampton et al., 2010b)]. b Pic-Clor 60 = 1,3-dichloropropene plus chloropicrin (40:60, w/w) at 280 kg·ha-1. c Within season means followed by different letters are significantly different according to Duncan’s multiple range test at 5%. NS *, **, *** Nonsignificant or significant at P ≤ 0.05, 0.01, or 0.001, respectively.

Treatment First harvest Second harvest Third harvest Total season harvest

XLa L M TM XL L M TM XL L M TM XL L M TM UM

Yield (Mg·ha-1)

Fall 2014 Pic-Clor 60b 19.0 5.7 3.6 28.3 1.4 2.2 2.7 6.3 0.3bc 1.8b 5.9b 8.0b 20.7a 9.7 12.2 42.6 2.5

Pic-Clor 60+fluensulfone 2.0 kg a.i·ha-1 15.7 5.9 3.0 24.7 1.1 3.0 3.0 7.2 1.1a 3.6a 11.3a 16.0a 18.0b 12.5 17.3 47.8 3.3

Pic-Clor 60+fluensulfone 2.8 kg a.i·ha-1 17.4 4.9 2.4 24.7 1.9 3.4 2.3 7.6 1.0a 4.1a 11.7a 17.0a 20.3a 12.4 16.4 49.1 4.1

P-value 0.09 0.33 0.20 0.07 0.33 0.16 0.41 0.11 0.03 0.02 0.007 0.007 0.05 0.10 0.07 0.08 0.3

Significance NS NS NS NS NS NS NS NS * * ** ** * NS NS NS NS

Spring 2016

Pic-Clor 60 36.1 2.5 0.0 38.6 20.9 4.3 1.2 26.4 6.8 2.9 1.0 10.6 63.7 9.7 2.2 75.7 7.7

Pic-Clor 60+fluensulfone 2.0 kg a.i·ha-1 35.0 1.9 0.2 37.0 23.3 4.3 1.1 28.7 7.1 3.2 1.5 11.9 65.3 9.4 2.9 77.5 7.6

Pic-Clor 60+fluensulfone 2.8 kg a.i·ha-1 36.1 1.9 0.3 38.2 23.4 4.9 1.7 30.0 5.8 2.5 1.4 9.8 65.3 9.4 3.3 78.0 7.2

P-value 0.85 0.23 0.66 0.75 0.61 0.67 0.54 0.37 0.51 0.57 0.44 0.33 0.89 0.92 0.35 0.77 0.85

Significance NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS

41

CHAPTER 3 EVALUATION OF FLUENSULFONE ON SOIL SPATIAL DISTRIBUTION AND

MOVEMENT, PLANT GROWTH, FRUIT YIELD, AND POSTHARVEST QUALITY OF TOMATO USING SEEPAGE IRRIGATION

Introduction

Florida has been the leading producer of fresh-market tomato (Solanum

lycopersicum L.) in the United States accounting for a harvested area and production

value of 34% and 36% of national totals in 2015, respectively (USDA, 2016). Following

the withdrawal of methyl bromide (MeBr) and the lack of satisfactory substitutes, the

management of root-knot nematodes (RKNs), Meloidogyne spp., has become critical in

the production of optimal tomato yields [U.S. Environmental Protection Agency (EPA),

2000; Noling, 2016]. Current alternatives have not been proven to provide a broad-

spectrum activity to the degree offered by MeBr (1995; Locascio et al., 1997; Snodgrass

et al., 2013; Noling, 2016; Di Gioia et al., 2016; Castillo et al., 2016). Based on their

movement in soil, chemical methods for managing RKNs in Florida fresh-market tomato

crops may be grouped into: fumigant and non-fumigant nematicides (Noling, 2014).

However, preliminary findings suggest that fumigant nematicides have not shown to

provide effective RKN management because of an uneven vertical distribution in the soil

profile and the survival of RKNs in deeper soil layers (Noling, 2016). Oxamyl (Vydate,

DuPont Crop Protection, Hayward, CA) and fluensulfone [5-chloro-2 (3,4,4-trifluoro-but-

3-ene-1-sulfonyl)-thiazole] (Nimitz, ADAMA Agricultural Solutions Ltd., Raleigh, NC) are

two non-fumigants that may be used to manage RKNs on fresh-market tomato crops in

Florida (Noling, 2016).

Fluensulfone belongs to the fluoroalkenyl thioester group with a water solubility,

boiling point, and vapor pressure of 545.3 mg·L-1, 282.5 oC, and 3.1×10-3 Pa,

42

respectively (Rubin et al., 2011). Fluensulfone has been found to exhibit an affinity to

organic matter (OM) and mobility in soils with high sand content and adsorption values

varying from 1.24 to 3.28 KF, (Oka et al., 2013; Morris, 2015). Also, fluensulfone has

shown low solubility in water (Rubin et al., 2011) and high mobility in the top 20 cm of

sandy soil including sandy clay loam and loamy sand (Morris, 2015). However, in heavy

clay soil, fluensulfone migration occurred to deeper layers (30 cm) from bed surface

when applied as a drench through drip irrigation (Rubin et al., 2011). Fluensulfone was

found to undergo a concentration decline throughout time and a rapid dissipation from

the soil within 10 days; however, fluensulfone still provided satisfactory RKN

management (Rubin et al., 2011). In addition, fluensulfone has systemic activity in the

plant and causes plant phytotoxicity; hence, product application will be required at least

seven days before transplanting or seeding. Hence, two to five days after application,

31.4 to 62.7 mm water·ha-1 needs to be applied to avoid seedling exposure to elevated

product residues (maximum residual concentration ~1.0 mg·kg-1) and to achieve

negligible phytotoxicity (E. Segal, personal communication).

Soil spatial distribution and movement of fluensulfone have not been studied in

sandy soils using seepage irrigation. Seepage irrigation has been widely used in Florida

because of its simplicity and low operating costs (Zotarelli et al., 2013; Ozores-Hampton

et al., 2015). In seepage irrigation, lateral furrows distribute water throughout the field

followed by the water moving horizontally beneath the soil surface to form a perched

water table, then the water diffuses upward toward plant root zones by capillary action

(Smajstrla and Muñoz-Carpena, 2011). Typically at planting, the water table is

maintained near the top 46-cm depth (measured from the top of the bed) and near the

43

top 61-cm depth throughout the growing season (Dukes et al., 2015). However, soil

moisture in the root zone is unevenly distributed across the field; plant rows closer to

the water furrows tend to be wetter than those rows located farther from the furrows

(Zotarelli et al., 2013; Ozores-Hampton et al., 2015). Normally, volumetric water content

of 12 - 18% is near field soil capacity and offers adequate moisture for plant growth

(Zotarelli et al., 2013). Because of the upward movement of water from capillarity action,

fluensulfone may concentrate in the upper bed profile causing severe phytotoxicity.

HYDRUS 2D/3D software package (PC-Progress, Prague, Czech Republic) was used

to model the effect of water flow and the soil distribution of fluensulfone residues in

seepage irrigation. HYDRUS 2D/3D has been used to simulate water flow, heat, and

solute transport (Šimůnek et al., 2006; Šejna and Šimůnek, 2007). For example,

Provenzano (2007) used the software to evaluate main dimensions of the wet soil

volume surrounding the emitter in drip irrigation in a sandy-loam soil. Therefore, the

objectives of this research were to study the effect of pre-plant incorporated

fluensulfone on soil distribution and movement and the effects on tomato plant growth,

fruit yield, and postharvest quality using seepage irrigation.

Materials and Methods

Field Preparation and Treatment Application

During the spring and fall of 2016, two experiments were conducted at the

University of Florida/Institute of Food and Agricultural Sciences/Southwest Florida

Research and Education Center (UF/IFAS/SWFREC) in Immokalee, FL. The soil type

was Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Haplaquods) (Natural

Resources Conservation Service, 2016). Soil sand, silt, and clay contents were 93.7,

44

2.3, and 4.0%, respectively. The OM content, pH, electrical conductivity (EC), and

cation exchange capacity (CEC) were 1.2%, 7.4, 56.5 µS cm-1, and 2.9 cmol·kg-1 in the

spring and 2.5%, 5.9, 26.2 µS·cm-1, and 2.0 cmol·kg-1 in the fall. Prior to bedding, on 2

Feb. and 18 Aug. 2016, fluensulfone treatments were broadcast applied on flat bed

surface area at 0 (control), 2.0 and 4.0 kg a.i·ha-1 arranged in a randomized complete

block design with four replications. Treatments were applied using a carbon dioxide

(CO2) pressurized backpack sprayer with a 91.4-cm-long boom consisting of four

nozzles, spaced 30.5 cm apart and with wide-angle-flat TT11002 spray tips (TeeJet

Technologies, Springfield, IL). Immediately after spraying but before planting, standard

dry fertilizer was broadcast as ‘bottom mix’ containing nitrogen-phosphorus-potassium

(N-P-K) at 34-49-37 kg·ha-1 (Olson et al., 2010) and incorporated into the soil to a depth

of 15 cm with a power rototiller. Then, raised beds (12-m-long x 20-cm-tall) were formed

with 1.8 m between centers using a 91-cm-wide bed shaper (Kennco Manufacturing,

Inc., Ruskin, FL). Two fertilizer bands were also applied with one on each bed shoulder

as ‘top mix’ (Olson et al., 2010) for a total N-P-K of 218-49-399 kg·ha-1 [sources:

ammonium nitrate (NH4NO3), triple superphosphate, and potassium sulfate (K2SO4)].

For weed management, halosulfuron (SandeaTM, Gowan Co., Yuma, AZ) was

simultaneously applied to the bed top at 35 g·ha-1. Beds were covered with 1.25-mm

thick virtually impermeable film mulch, black-on-white and white-on-black during the

spring and fall of 2016, respectively (Winfield Solutions, LLC., Immokalee, FL). Each of

the treatment plots consisted of three beds. Seven days after treatment application

(DAA), on 9 Feb. and 25 Aug. 2016, six-week-old seedlings of large, round,

determinate, fresh-market tomato ‘HM 1823’ (HM.CLAUSE, Inc., Davis, CA) grown in

45

128-cell styrofoam trays (Mobley Plant World, LaBelle, FL), were transplanted 61 cm

apart in a single row for each bed establishing 60 plants per plot or a population of

8,966 plants·ha-1. The crop was irrigated using seepage irrigation with a water furrow

located every six beds. Management of pests and foliar pathogens was accomplished

based on weekly scouting reports and UF/IFAS recommendations (Freeman et al.,

2015).

Data Collection

Averages for minimum, mean, maximum daily air temperatures, and for total

rainfall accumulation, daily solar radiation, and evapotranspiration (ET) were recorded

by the Florida Automated Weather Network (FAWN) located at the UF/IFAS/SWFREC

in Immokalee, FL. Irrigation was managed by installing monitoring wells made from a

1.2-m-long, 10-cm-diameter polyvinyl chloride (PVC) pipe (Smajstrla and Muñoz

Carpena, 2011). Monitoring wells were installed at the center of each replication and

water table depth was monitored weekly throughout the growing season. To indicate

water levels, a float was attached to the bottom end of the PVC pipe, and marks were

made every 2.54 cm to show water table depth below the polyethylene mulch.

Tensiometers (Irrometer Company, Inc., Riverside, CA) were located at the center of

each replication to monitor soil moisture by measuring the soil water matric potential

weekly throughout the growing season. Fluensulfone concentration in the soil and

gravimetric water content were measured immediately after treatment application, and

subsequently at 2, 7, 14, and 21 DAA. Five soil cores were randomly collected to the

depths of 0-10 cm and 10-20 cm at the center bed of each plot and mixed to create one

composite sample. Soil cores were collected using a 25.4-cm-diameter recovery probe

46

with individual acetate liners (AMS, Inc., American Falls, ID). Subsamples of 100 g were

oven dried at 105 oC for 24 h and weighed to determine soil moisture. Then, frozen

subsamples were sent to EAG Laboratories, Hercules, CA, where soil concentration of

fluensulfone was determined by liquid chromatography tandem mass spectrometry

(LC/MS-MS). To simulate fluensulfone movement in seepage irrigation at 6, 20, and 30

DAT for the spring and at 8, 21, and 30 DAT for the fall, HYDRUS 2D/3D software (PC-

Progress, Prague, Czech Republic) was used by ADAMA Agricultural Solutions Ltd.,

Airport City, Israel.

Roots, stems, leaves, and fruits of two plants per plot were randomly collected

and oven dried at 65 oC until constant weight at 30, 60, and 90 DAT to determine dry

weight (DW) (Mills and Jones, 1996). Total plant DW was calculated by adding the DW

of the roots, stems, leaves, and fruits. Tomato fruit of 10 representative plants at the

center bed for each plot were manually harvested and weighed three times at mature-

green stage at 85, 92, and 98 DAT during the spring and at 81, 95, and 102 DAT during

the fall of 2016. Tomato fruit yield was classified into marketable and unmarketable.

Marketable fruit yield was graded according to USDA size category specifications—

extra-large (diameter > 7.00 cm), large (6.35 to 7.00 cm), and medium (5.72 to 6.43 cm)

(USDA, 1997). Tomato fruit were considered unmarketable according to the presence of

defects such as sunscald, scratch, off-shape, catface, and graywall (Jones et al., 1991;

Ozores-Hampton et al., 2010b). At first harvest, 20 mature-green tomato fruit per plot

were collected, placed in paper bags, and exposed to ethylene at 20 °C and 85 to 90%

relative humidity until they achieved stage two of ripeness (Sargent et al., 2014) at

Gargiulo, Inc. packing house in Immokalee, FL. After achieving stage two, tomatoes

47

were transported to UF/IFAS/SWFREC, Vegetable Horticulture Laboratory in

Immokalee, FL, where they were allowed to achieve table-ripe stage at room

temperature (23 to 24 °C) for postharvest quality assessments (Ozores-Hampton et al.,

2010b). Four fruit from each plot were then selected to determine their firmness, which

is based on the amount of fruit deformation recorded by an 11-mm probe when a 1-kg

force is applied to the fruit “equatorial” area for 5 s by a portable digital firmness tester

(Model C125EB, Mitutoyo Co., Aurora, IL). Exterior color for each of the same four fruit

was measured using a one to six scale where one = green and six = red (USDA, 1997).

One-fourth of each of the four fruit was selected, and the fourths were then combined to

measure total soluble solids [(TSS), °Brix] and pH. The samples were homogenized and

centrifuged (Model Sorval ST16; Thermo Scientific, Waltham, MA) at 7177 gn for 20

min. After that, the supernatant was filtered using cheesecloth. The filtered was used to

measure TSS with a portable refractometer (Model Eclipse 45-02; Bellingham + Stanley

Inc., Suwanee, GA) and pH with a pH meter (Orion 4 star benchtop; Thermo Electron

Co., West Palm Beach, FL).

Statistical Analysis

Because soil chemical and physical properties varied between seasons, all data

parameters were analyzed separately by season. Using the TTEST procedure in SAS

software package (SAS 9.3, SAS Institute Inc., Cary, NC, 2012), fluensulfone soil

concentrations among the two rates were subjected to Student’s t-distribution at 5%

confidence level. Plant DW (roots, stems, leaves and fruits), yield, and postharvest fruit

quality parameters were subjected to analysis of variance (ANOVA) using the GLM

48

procedure and means were separated according to Duncan’s Multiple Range Test at

5% confidence level.

Results

Weather Conditions, Water Table Depth, and Soil Water Matric Potential

Averages for minimum, mean, and maximum daily air temperatures during the

growing season (planting to third harvest) were 14.5, 21.6, and 29.4 oC in the spring

and 19.2, 24.4, and 31.5 oC in the fall, respectively (Table 3-1). Average daily solar

radiation was 219.3 and 174.0 W·m-2 in the spring and fall of 2016, respectively. Total

rainfall accumulation and ET were 186.4 and 350.8 mm in the spring and 300.0 and

318.8 mm in the fall, respectively. Daily air temperatures were within the range of

average temperatures recorded in the previous 10 years (2006-2015) and there were no

freezing events reported for both seasons. Daily solar radiation, however, was 14.8 and

12.7 W·m-2 lower than the historical 10-year average. Total rainfall accumulation and ET

for the spring and fall seasons were 13.1 and 12.3 mm lower and 12.7 and 37.9 mm

lower than the previous 10-year average, respectively.

Water table depth in the monitoring wells fluctuated between 53 and 82 cm and

46 and 87 cm in the spring and fall seasons, respectively (Figure 3-1). Water table

levels were closer to the bed top during the first five weeks of the growing season. At

planting, on 9 Feb. (spring) and 25 Aug. (fall), water table levels were raised closer to

the bed top to facilitate the establishment of the transplants and ensure adequate

nutrient uptake. As a result of rainfall events recorded on 13 and 14 Aug. (24 mm)

during the fall, water table reached the highest level of 46 cm from bed top. Soil water

matric potential fluctuated between 2.3 and 11.8 kPa and 2.8 and 11.8 kPa in the spring

49

and fall seasons, respectively (Figure 3-2). At planting, soil tension was low for the

spring (2.3 kPa) and fall (2.8 kPa) seasons to facilitate plant lower energy requirements

to extract water from the soil.

Fluensulfone Concentration and HYDRUS 2D/3D Modeling

During the spring of 2016, fluensulfone soil residues measured at 0-10 cm deep

from the top of the bed were not statistically different among the two treatments at 0, 2,

14, 21 DAA [P > 0.05 (Figure 3-3)]. However, at seven DAA, soil residue of fluensulfone

at 4.0 kg a.i·ha-1 (1.12 mg·kg-1) was higher than at 2.0 kg a.i·ha-1 (0.55 mg·kg-1) (P =

0.05). Fluensulfone soil residues measured at 10-20 cm deep were not statistical

different at 0, 2, 7, 14 DAA (P > 0.05), except at 21 DAA in which fluensulfone at 4.0 kg

a.i·ha-1 was higher (2.22 mg·kg-1) than at 2.0 kg a.i·ha-1 (0.99 mg·kg-1) (P = 0.03).

During the fall of 2016, fluensulfone soil residues measured at 0-10 cm deep at 0, 2, 14,

21 DAA, were not statistically different among the two treatments (P > 0.05). However,

at seven DAA, soil residue of fluensulfone at 4.0 kg a.i·ha-1 (2.38 mg·kg-1) was higher

than at 2.0 kg a.i·ha-1 (0.47 mg·kg-1) (P = 0.04). Fluensulfone soil residues measured at

10-20 cm deep were not statistical different at 0, 2, and 21 DAA (P > 0.05). Soil residue

of fluensulfone at 4.0 kg a.i·ha-1 was higher than the lower treatment at 7 and 14 DAA

with 0.99 and 0.92 mg·kg-1 at 10-20 cm deep, respectively (P = 0.001 and 0.01).

During the spring conditions, at six DAA, simulation of fluensulfone at 2.0 kg

a.i·ha-1 with HYDRUS 2D/3D showed the highest soil residue concentration (1.23

mg·kg-1) at 0 cm deep (bed surface) (Figure 3-4). Similarly, during the fall, at eight DAA,

the highest soil residue concentration (1.01 mg·kg-1) occurred at 0 cm deep (Figure 3-

5). In the spring, fluensulfone at 2.0 kg a.i·ha-1 appeared to undergo a rapid dissipation

50

to the bed shoulders and upward movement, with the highest soil concentration of 0.36

mg·kg-1 found at 0 cm deep at 20 DAA. In the fall, at 21 DAA, the highest residual

concentration of 0.35 mg·kg-1 was found at 11 cm deep. HYDRUS 2D/3D predicted that

at 30 DAA, the highest residual concentrations of 0.22 mg·kg-1 and 0.29 mg·kg-1 were

found at 0 and 9 cm for the spring and fall seasons, respectively.

In the spring, at six DAA, simulation of fluensulfone at 4.0 kg a.i·ha-1 accounted

for the highest soil residue concentrations of 1.40 mg·kg-1 allocated at 12 cm deep from

bed top. A rapid dissipation occurred at 20 DAA to bed shoulders with a concentration

of 0.50 mg·kg-1 at 0 cm deep. Lastly, at 30 DAA, HYDRUS 2D/3D predicted a

concentration decrease to 0.32 mg·kg-1 found at 0 cm. In the fall, at eight DAA,

simulation of fluensulfone at 4.0 kg a.i·ha-1 accounted for the highest soil residue

concentrations of 1.73 mg·kg-1 allocated at 4 cm deep from bed top. A rapid dissipation

occurred at 21 DAA to bed shoulders with a concentration of 0.61 mg·kg-1 at 10 cm

deep. Finally, at 30 DAA, HYDRUS 2D/3D predicted a concentration decline to 0.5

mg·kg-1 found at 9 cm.

Plant Growth, Fruit Yield, and Postharvest Quality

During the spring, total plant and fruit DW at 90 DAT in the non-treated control

were on average 29 and 34% higher than both fluensulfone treatments, respectively

(Table 3-2). Similarly, during the fall, at 60 DAT, fruit DW in the non-treated control was

on average 18% higher than both fluensulfone treatments whereas there was no effect

of fluensulfone on total plant DW at 60 DAT (P > 0.05). However, in the spring and fall

seasons, DW of roots, stems, and leaves were not affected by fluensulfone treatments

on any sampling dates (P > 0.05). Total plant and fruit DW were not affected by

51

fluensulfone rates at 30 and 60 DAT and at 30 and 90 DAT in the spring and fall

seasons, respectively P > 0.05).

In the spring, at third harvest, fluensulfone at 4.0 kg a.i·ha-1 accounted for the

highest large and medium size categories and total marketable and unmarketable yield

with an increase of 81, 70, 64, and 121%, respectively (Table 3-3). Total season large

and medium fruit were on average 43 and 61% higher with fluensulfone at 4.0 kg a.i·ha-

1. However, there was no effect on the extra-large fruit size category (P > 0.05). Total

season extra-large, total marketable and unmarketable yields were not affected by any

fluensulfone treatments (P > 0.05). Application of fluensulfone did not have an effect on

any tomato fruit size categories or total marketable and unmarketable yield at first,

second, and first and second harvests combined (P > 0.05). In the fall, at first harvest,

fluensulfone at 2.0 kg a.i·ha-1 and the non-treated control accounted for the highest

extra-large fruit size category and total marketable yield (Table 3-3). However,

fluensulfone at 4.0 kg a.i·ha-1 and the non-treated control accounted for equal yields. At

third harvest, fluensulfone at 4.0 kg a.i·ha-1 accounted for the highest large and medium

size categories and total marketable yield with an increase of 34, 52, and 39%,

respectively, whereas there were no significant differences for the unmarketable yield (P

> 0.05). Fluensulfone treatments did not have an effect on any tomato fruit size

categories or total marketable and unmarketable yield at second, first and second

harvests combined and total season yield (P > 0.05).

Postharvest evaluation as fruit deformation, exterior color, TSS, and pH were not

influenced by any fluensulfone treatment during the spring or fall season [P > 0.05,

(Table 3-4)].

52

Discussion

Simulation by HYDRUS 2D/3D suggested that fluensulfone concentrated in the

shallower soil layers based on soil properties and weather conditions. However, soil

fluensulfone concentrations were below the threshold to cause plant phytotoxicity during

the spring and fall seasons. During the spring, which had cooler temperatures and lower

rainfall, fluensulfone concentrated in the upper layer, showing a dissipation over time at

six DAA when water table levels reached 53 cm from bed top. Rubin et al., 2011

demonstrated that when fluensulfone was applied through drip irrigation, the chemical

migrated to deeper layers (30 cm), which can be attributed to the downward movement

of water by gravity. In contrast, using seepage irrigation, HYDRUS 2D/3D modeling

suggests that fluensulfone residues concentrated in the soil upper layers, which can be

ascribed by the upward movement of the water table.

During the fall, which had higher temperatures, rainfall, and OM, fluensulfone

residues were located at 5-11 cm whereas in the spring the residues migrated to

surface of the soil (0 cm). Previous studies with clay, Hamra sandy, and loamy sand

soils have shown that fluensulfone exhibits an affinity to OM, potentially limiting the

movement in the soil through binding by sorption [Van der Waal's forces, hydrogen

bonding, hydrophobic bonding (Oka et al., 2013; Morris et al., 2015; Moss et al., 1975;

Leistra and Smelt, 1981; Bollag et al., 1992; Whitehead, 1988)]. Therefore, high OM

content in the fall (2.5%) could possibly explain retention of fluensulfone, but may not be

considered as the only factor since during both seasons, water upward flow using

seepage irrigation appeared to be the prevailing factor on the fate of fluensulfone.

These findings were expected since fluensulfone, as a non-fumigant, moves through the

53

soil water, which suggests that during the first weeks of the growing seasons,

fluensulfone transport and fate were governed by water flow and less by chemical

reactions (adsorption) or biological degradation (E. Segal, personal communication).

Although symptoms of phytotoxicity did not appear in either season, each

fluensuflone treatment yielded the lowest total plant and fruit DW in the spring at 90

DAT and the lowest total fruit DW in the fall at 60 DAT. However, fluensulfone

treatments did not decrease root, stem, leaf DW, or fruit yield. Reduction in plant and

fruit DW could be attributed to fluensulfone systemic activity (Oka et al., 2013). Recent

studies by Morris et al., 2016 have presented that foliar applications of fluensulfone

caused a reduction on plant DW in eggplant (Solanum melongena) and tomato. In

addition, high rates of fluensulfone (12 g a.i·l-1) were phytotoxic to both crops at 12 and

28 DAA. Several studies have verified that some systemic chemicals have an influence

on plant growth and production (Pless et al., 1971; Lee, 1977; Olofinboba and

Kozlowski, 1982; Reddy et al., 1986; Araya et al., 1988; Cranshaw and Thorton, 1988).

However, there is no information on fluensulfone mode of absorption, translocation, and

detoxification within the plant, translocatable form, or the concentration of molecules in

the plant cells, especially in the fruit. Further studies are needed to assess the ability of

fluensulfone to penetrate plant cells and the implications on DW.

Following label recommendation, when crop transplanting needs to be at least

seven DAA, residual concentrations of fluensulfone at 2.0 and 4.0 kg a.i·ha-1 were 0.55

and 1.12 mg·kg-1 and 0.47 and 2.38 mg·kg-1 at 0-10 cm deep for the spring and fall

seasons, respectively. Twenty-one DAA, which is the planting interval for some

available pre-plant fumigants used extensively by the vegetable industry, the residual

54

concentrations of 2.0 and 4.0 kg a.i·ha-1 at 0-10 cm deep decreased to 0.46 and 1.42

mg·kg-1 and 0.37 and 1.38 for the spring and fall seasons, respectively. Therefore,

delayed transplanting after seven DAA of fluensulfone application could be a possible

strategy to avoid a decrease in DW.

Pre-plant incorporation of fluensulfone in seepage irrigation did not reduce fruit

yield or negatively influence tomato fruit postharvest quality. Overall, total marketable

yield obtained during both seasons were in accordance with those observed by Ozores-

Hampton et al. (2012, 2015) in Immokalee, FL. In addition, fluensulfone did not

decrease extra-large fruit yield which will be the grower’s preferred size category

because they are valued at premium prices (Bierlen and Grunewald, 1995). These

results were not expected since fluensulfone residual concentration of approximately

1.0 mg·kg-1 caused phytotoxicity when applied through foliar spray or drip injection (E.

Segal, personal communication). However, our results suggest that fluensulfone

residual concentrations greater than 1.0 mg·kg-1 did not decrease fruit yield in seepage

irrigation. However, further research needs to be conducted with replicated years and

different weather conditions to corroborate the results of these studies. In addition,

studies are needed to assess fluensulfone nematicidal efficacy in seepage irrigation.

Summary

Using seepage irrigation, fluensulfone concentrated in the upper bed profile as

predicted by HYDRUS 2D/3D software with soil residues of 2.0 and 1.01 mg·kg-1 at six

DAA and 0.36 and 0.35 mg·kg-1 at 21 DAA for the spring and fall seasons, respectively.

Fluensulfone treatments showed lower total plant and fruit dry weight at 90 DAT during

the spring and lower fruit DW at 60 DAT during the fall. However, fluensulfone

55

treatments below 2.0 mg·kg-1 did not show phytotoxicity or decrease root, stem, leaf

DW, fruit yield, or impact postharvest fruit quality. These results suggest that the pre-

plant incorporation of fluensulfone did not negatively influence fresh-market tomato

production grown in sandy soils using seepage irrigation. However, the movement and

distribution of fluensulfone and the effects on plant growth and yield need to be further

evaluated for different climates, soil types, and crops.

56

Table 3-1. Summary of minimum (Min.), mean, and maximum (Max.) daily average air temperatures, solar radiation, total rainfall accumulation, and evapotranspiration (ET) during the spring and fall of 2016, and 10-year spring and fall averages for Immokalee, FL.

a ET = Evapotranspiration is presented as the United Nations Food and Agriculture Organization (FAO) Penman-Monteith. bThe temperature and solar radiation averages, and rainfall and evapotranspiration totals were recorded daily from 2 Feb. through 18 May and from 18 Aug. through 5 Dec. 2016. Data source: Florida Automated Weather Network station located at University of Florida/Institute of Food and Agricultural Science/Southwest Florida Research and Education Center in Immokalee, FL (http://fawn.ifas.ufl.edu/).

Period Temperature (°C)

Solar radiation

Total rainfall

ETa

Min. Mean Max. (W·m-2) (mm) (mm)

Spring

Februarya 10.6 17.2 24.5 176.3 62.0 63.5

March 15.4 21.8 29.3 200.3 17.3 94.7

April 15.2 22.9 31.2 248.6 34.8 117.6

May 16.9 24.4 32.5 252.0 72.4 74.9

Average/total 14.5 21.6 29.4 219.3 186.4 350.8

Spring 10-year average 13.5 20.9 29.2 234.1 199.5 363.1

Fall

August 24.3 28.0 34.2 203.0 68.6 55.6

September 23.4 27.3 34.0 194.7 184.7 109.5

October 19.7 24.4 30.7 171.5 45.5 86.1 November 12.6 20.0 28.9 159.4 0.8 58.2 December 16.0 22.0 29.8 141.3 0.5 9.4

Average/total 19.2 24.4 31.5 174.0 300.0 318.8

Fall 10-year average 18.7 23.9 31.3 186.7 337.9 323.3

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Figure 3-1. Water table level (from the top of the bed) in seepage-irrigated fresh-market tomato crops grown during the

spring and fall seasons of 2016 in Immokalee, FL. Means of four replications. Vertical bars represent ± SE.

58

Figure 3-2. Soil water matric potential in seepage-irrigated fresh-market tomato crops grown during the spring and fall

seasons of 2016 in Immokalee, FL. Means of four replications. Vertical bars represent ± SE. Readings of 0–5 kPa: soils are saturated or nearly saturated; 10–15 kPa: crops should be irrigated as soon as possible; 25 kPa and higher: plants probably present symptoms of water stress (Migliaccio et al., 2012).

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Figure 3-3. Fluensulfone concentration in the soil profile at 0-10 and 10-20 cm deep from the top of the bed in seepage-

irrigated fresh market tomatoes during the spring and fall seasons of 2016 in Immokalee, FL. Vertical lines represent planting dates.

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Figure 3-4. HYDRUS 2D/3D simulation describing water flow and fate of fluensulfone treatments at 6, 20, 30 days after

treatment application (DAA) in seepage irrigation conditions during the spring of 2016 in Immokalee, FL.

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Figure 3-5. HYDRUS 2D/3D simulation describing water flow and fate of fluensulfone treatments at 8, 21, 30 days after

treatment application (DAA) in seepage irrigation conditions during the fall of 2016 in Immokalee, FL.

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Table 3-2. Effect of pre-plant application of fluensulfone on plant dry biomass on seepage-irrigated fresh-market tomato crops grown during the spring and fall seasons of 2016 in Immokalee, FL.

aDAT = days after transplanting bTotal represents roots, stems, and leaves. cWithin columns, means followed by different letters are significantly different according to Duncan’s multiple range test at 5%. NS, *, **, ***, Non-significant or significant at P ≤ 0.05, 0.01, 0.001, respectively.

Treatment

Dry biomass (g·plant-1)

Spring (DATa)

30 60 90

Root Stem Leaves Totalb Root Stem Leaves Fruits Total Root Stem Leaves Fruits Total

Non-treated control 2.6 4.2 11.6 18.5 7.2 57.5 131.4 125.4 321.4 8.1 82.6 192.0 399.2ac 682.0a Fluensulfone 2.0 kg a.i·ha-1 3.4 6.5 14.5 24.3 6.9 61.8 139.3 118.9 326.9 8.0 81.9 176.2 257.5b 523.6b Fluensulfone 4.0 kg a.i·ha-1 2.5 5.4 14.2 22.1 6.0 58.2 137.6 117.5 319.2 5.9 82.8 176.7 267.0b 532.4b P-value 0.28 0.16 0.06 0.08 0.39 0.39 0.59 0.60 0.91 0.10 0.98 0.80 0.01 0.05 Significance NS NS NS NS NS NS NS NS NS NS NS NS ** * Fall Non-treated control 9.9 23.6 52.7 86.2 15.9 77.6 158.7 110.3a 362.4 23.3 99.9 220.6 233.0 576.8 Fluensulfone 2.0 kg a.i·ha-1 8.1 22.9 46.3 77.3 13.6 74.4 148.0 92.5b 328.5 21.5 97.4 201.2 210.7 530.8 Fluensulfone 4.0 kg a.i·ha-1 9.1 23.8 53.7 86.5 13.9 80.8 161.8 88.5b 345.0 20.2 93.8 201.0 211.0 525.9 P-value 0.56 0.94 0.55 0.50 0.57 0.49 0.56 0.02 0.33 0.56 0.81 0.46 0.85 0.68 Significance NS NS NS NS NS NS NS * NS NS NS NS NS NS

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Table 3-3. Effect of pre-plant application of fluensulfone on first, first and second harvests combined, and total season harvest (three harvests combined) marketable and unmarketable tomato fruit yield graded by size categories during the spring and fall seasons of 2016 in Immokalee, FL.

a XL = extra-large (diameter greater than 7.00 cm); L = large (6.35 to 7.00 cm); M = medium (5.72 to 6.43 cm); ); TM = total marketable, UM = unmarketable [fruit with defects such as sunscald, scratch, off-shape, catface, and graywall (Jones et al., 1991; Ozores-Hampton et al., 2010b)]. b Within columns, means followed by different letters are significantly different according to Duncan’s multiple range test at 5%.

NS, *, **, ***, Non-significant or significant at P ≤ 0.05, 0.01, 0.001, respectively.

Treatment First harvest First and second harvests Total season harvest

XLa L M TM XL L M TM XL L M TM UM

Yield (Mg·ha-1)

Spring Non-treated control 43.6 1.1 0.3 45.0 60.2 4.0 0.9 64.5 63.8 7.8bb 3.3b 74.2 8.5 Fluensulfone 2.0 kg a.i·ha-1 38.4 1.1 0.2 39.7 54.3 2.9 0.6 57.8 60.4 6.2b 2.8b 69.4 8.6 Fluensulfone 4.0 kg a.i·ha-1 37.4 1.2 0.1 38.7 53.3 4.2 1.0 58.4 60.5 10.5a 4.9a 75.9 8.6 P-value 0.21 0.89 0.51 0.14 0.27 0.22 0.59 0.22 0.80 0.001 0.01 0.46 0.99

Significance NS NS NS NS NS NS NS NS NS ** * NS NS

Fall

Non-treated control 14.9ab 9.3 2.3 26.5ab 23.1 16.0 3.8 42.9 31.4 26.3 11.3 68.9 2.6

Fluensulfone 2.0 kg a.i·ha-1 18.1a 8.5 1.7 28.3a 25.9 13.3 2.5 41.8 32.9 21.2 9.3 63.4 2.8 Fluensulfone 4.0 kg a.i·ha-1 12.3b 8.3 2.3 22.9b 20.4 13.6 3.2 37.3 30.7 26.2 13.3 70.2 2.2 P-value 0.03 0.71 0.54 0.03 0.21 0.40 0.48 0.61 0.89 0.06 0.10 0.11 0.54

Significance * NS NS * NS NS NS NS NS NS NS NS NS

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Table 3-4. Fluensulfone treatment effects on tomato fruit firmness (expressed as fruit deformation), exterior fruit color, pH, and total soluble solids at first harvest during the spring and fall seasons of 2016 in Immokalee, FL.

Treatment Deformation

(mm) (8 DAFHa)

Color stage (1–6 scale)b

pH Total soluble solids (°Brix)

Spring Non-treated control 2.83 5.38 4.00 3.95 Fluensulfone 2.0 kg a.i·ha-1 2.68 5.25 3.90 3.96 Fluensulfone 4.0 kg a.i·ha-1 2.79 5.63 3.90 3.89 P-value 0.49 0.11 0.07 0.90 Significancec NS NS NS NS Fall Non-treated control 2.20 5.44 3.90 4.50 Fluensulfone 2.0 kg a.i·ha-1 2.52 5.69 3.80 4.53 Fluensulfone 4.0 kg a.i·ha-1 2.21 5.56 3.95 4.54 P-value 0.19 0.51 0.24 0.56 Significance NS NS NS NS

aDAFH = Days after first harvest b1 = green and 6 = red (USDA, 1997) cNS = Non-significant at P > 0.05.

65

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BIOGRAPHICAL SKETCH

Gilma Castillo was born in Yoro, Honduras in 1992. She graduated from Ave

Maria University, FL in 2013 with a B.A. in biology and a minor in chemistry. In 2014,

she joined the Vegetable Horticulture Program in Immokalee, FL as part of her optional

practical training (OPT). In August 2016, she started her graduate studies at University

of Florida to pursue a master’s degree in horticultural sciences. Her research focuses

on the evaluation of the efficacy of fluensulfone to manage root-knot nematodes on drip-

irrigated fresh-market tomato and on the study of the distribution and movement of pre-

plant-incorporated fluensulfone in sandy soils irrigated via a seepage method.