Possible IPM approaches to pest management under HLB

Lukasz StelinskiUniversity of Florida, Entomology and Nematology Department, CREC, Lake

Alfred, FL

• Regular monitoring

• Combination of control methods

• Minimizing harm to beneficials and theenvironment

• Deciding whether treatment is necessary after assessing the pest populations

Key Features of IPM

The Economic Threshold

InjuryPhysical or physiological lossesof plants caused by pests: Reduced leaf areas or photosynthesis

Feeding

injury

Injury does not always cause damage

DamageEconomic losses of plants caused by pests:Reduced yield or quality

The difference between injury and damage

Economic

Damage

The relationship between injury and damage

Figuring out the economics of pest control

The Economic Injury Level (EIL)

ost

Value Injuryamage

The Economic Injury Level (EIL)

The Economic Injury Level (EIL)

Problems with use of Economic Injury Level (EIL)

EIL under citrus greening (Stansly et al. 2017)

Calendar applications: 100.2 ACP threshold: 40.7 ACP threshold: 2No insecticide: 1

Treatments: # of insecticide sprays:

HLB was 80% and higher

Looked at ACP suppression and yield, calculating cost of ACP management

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Jul-10 Jan-11 Aug-11 Feb-12 Sep-12 Mar-13 Oct-13

ACP

cum

ulat

ives

per

plo

t 0.7 thrsldCalendar0.2 thrsldNo spray

Location 1

0

1000

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7000

Aug-10 Jan-11 Jun-11 Nov-11 Apr-12 Aug-12 Jan-13 Jun-13 Nov-13

ACP

cum

ulat

ive

per p

lot

Calendar

No spray

0.2 thrsld

0.7 thrsld

Location 2

Cumulative ACP Adults in Stem Tap Samples

Highest yield in Monthly spray (Calendar)

0.2/tap—Highest profit

Highest yield in Monthly spray (Calendar)

No difference in profitbetween Calendar and 0.2/tap

What's the best EIL for your situation?

0.2/tap?

Keeping ACP down seems to help yield

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2009 2010 2011 2012 2013 2014 2015

Boxe

s per

Acr

eUntreated

Nutrition

Insecticide

Insecticide + nutrition

b b

a

b aa

b

abb

c

ab a

c

abb

a

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aba a

a

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b ab

Citrus plants cv Valencia

Challenged with:

1) CLas-infectedor

2) Non-infected ACP 1. One-time inoculation

2. Pulsed inoculation

(Periodic invasions)

3. Continuous inoculation

(Constantly reproducing

resident population)

Challenging plants to infestation and pathogen under controlled conditions

Preventing a standing infestation with or without pathogen prolongs tree life

CLas titer CLas-

infectedACP

Poor(several dying)

Intermediate

Good

Poor(some dying)

Good

Good

Plant healthNon-

infectedACP

One time

Constant

Pulsed

pg o

f CLa

s D

NA

per 1

0 ng

of p

lant

DN

A

Date

CLas titer in mature leaves

110264300

Gove 1

Gove 2

Gove 3

Gove 1

Gove 2

Gove 3

2018 Nonreplicated trial: Fewest fruit per tree where psyllid numbers were highest

Treatment

Selection 1 Selection 2 Selection 3 Selection 4

Mar 24, 2019 May 5, 2019 Jun 10, 2019 Jun 22, 2019Apr 22, 2019 May 31,2019 Jun 28, 2019 -----------------

Rotation 1 dimethoate cyantrniliprole fenpropathrin diflubenzuron

Rotation 2 fenpropathrin dimethoate cyantrniliprole imidacloprid

Rotation 3 thiamethoxam clothianidin thiamethoxam imidacloprid

Rotation schedules effectively suppress resistance; consequences of not rotating show up nearly immediately

Applciation timesF0 F1 F2

RR

ratio

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Applciation times F0 F1 F2 F3 F4

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ista

nce

ratio

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Things ‘get real’; fast! Location 1

Location 2

We observed 200-500 fold resistance with 2 back-to backs;~2000 fold after 3 consecutivefailures to rotate

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ACP

adul

t per

tapp

ing

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ACP

adul

t per

tapp

ing

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Location 1

Location 2

Once we start to see > 100 fold resistance in the lab, failures in the field are evident.

Some rotations emerging as superior in terms of population suppression and resistance management interaction

Rotation 1

Rotation 1

3

3

2

2

Does order of the sequence matter?

Treatment May June July September October

Rotation A dimethoate abamectin + thiamethoxam

fenpropathrin diflubenzuron imidacloprid

Rotation B imidacloprid fenpropathrin abamectin + thiamethoxam

dimethoate diflubenzuron

Rotation C thiamethoxam diflubenzuron dimethoate imidacloprid fenpropathrin

No

fenpropathrin dimethoate cyantraniliprole imidacloprid

IGR Oil Kaolin butenolide

Kaolin: Non-toxic particle film; affects ACP ability to grasp/feed on leaves

Studies in FL citrus began around 2005: (Hall, D. G., S. L. Lapointe, and E. J. Wenninger. 2007. Effects of a particle film on biology and behavior of Diaphorina citri (Hemiptera: Psyllidae) and its infestation in citrus. J. Econ. Entomol. 100: 847-854.)

It’s not full proof; as leaves grow surfaces become unprotected; like anything applied to foliage in FL, can wash off; does not prevent HLB. Nonetheless, several studies have indicated efficacy against ACP comparable to toxic poisons.

Reflective mulch to repel ACP

Summary: Ways to Lower ACP Control Costs and Resistance

1. Thresholds can guide spray frequency and reduce sprays2. Target control to reduce ACP in flush

– Preemptive sprays may be best– Don’t let a standing population linger

3. Use border sprays to control psyllids where they congregate and reduce sprays to whole block– Selective products for whole block sprays– Cheap products for border sprays

4. Conserve beneficials by eliminating unnecessary sprays5. Rotate between at least 5 modes of action6. Other techniques (mulches, kaolin, mesh, windbreaks) either

available and more coming (attract-and-kill)