All About Lygus Management in Strawberry Production

Frank ZalomFrank ZalomDepartment of EntomologyDepartment of Entomology

UC DavisUC Davis

UCCE Strawberry Lygus Bug SeminarWatsonville, CA - April 18, 2013

Six steps of IPM

• Identify the pest - identification and biology• Assess the threat - sampling and thresholds• Assess the management options and select

tactics - IPM strategies and tactics• Apply the tactics• Evaluate results - did it work? more sampling• Record the results for future planning - for

next year; prevention and other strategies

From ENT 110, Arthropod Pest Management

Biology and hostsSamplingCultural controlsBiological controlsChemical controls

April 18, 2013

Lygus bug seminarLygus bug seminar

• Evaluate results - did it work?• Record results for future planning -

prevention and other strategies?

Infested second year plantings Weedy hosts around fields Alternate crops and cover crops (snow peas, fava beans, etc.)

PepperweedMustards & wild radish

Blackie Rd. near CastrovilleSpence Rd. near Salinas

Lygus - sourcesLygus - sources

Lygus weed and crop hosts in central coast areasW E E D H O S T F E B M A R A P R M A Y J U N J U L A U G

W i l d r a d i s h

M u s t a r d s

C h i c k w e e d

F i l a r e e

R e d m a i d s

S h e p h e r d ' s - p u r s e

L u p i n e s

C a l i f o r n i a b u r c l o v e r

C o m m o n g r o u n d s e l

P i n e a p p l e w e e d

M i l k t h i s t l e

S p i n y c o c k l e b u r

C o m m o n c o c k l e b u r

S o w t h i s t l e

M a l l o w ( c h e e s e w e e d )

C a l i f o r n i a p o p p y

C u r l y d o c k

S m a r t w e e d

K n o t w e e d

L a m b s q u a r t e r s

P i g w e e d

C O V E R C R O P S

C l o v e r

F a v a b e a n s

V e t c h

medium

low high

• Flowering plants attract Lygus, but they can also serve as a source of adults in fields

• Control weeds or trap crops in Spring while Lygus are still nymphs

Monterey County

Remember - only Lygus adults Remember - only Lygus adults can move to strawberry fields can move to strawberry fields

Monitoring, Monitoring, Monitoring…..Monitoring, Monitoring, Monitoring…..Determine when to make a control action….

• Monitor alternate hosts (including infested older strawberry plantings) to determine when adults are present that may move into strawberries

• Treat or destroy the alternate hosts, if possible, before nymphs become adults

• Monitor Fall-planted strawberries to determine when the first adults appear to establish the biofix

• Treat with appropriate products depending on the age structure of a population (e.g. Rimon is a growth regulator, so will only be effective on nymphs), save the products that will also kill adults for later

Spread out samples over a 200 foot section of strawberry bed.

A-vac

Beating hoop or tray

Sweep net - for weeds, trap crops, and other crops Beating hoop - treatment level is 1 Lygus nymph or adult in 20 plants A-vac - treatment level is 1 Lygus nymph or adult in 10 plants

Monitoring guidelinesMonitoring guidelines

Using the Lygus DD model

Biofix 2

Biofix 1

Monitoring…..

Second Year FieldFirst Year FieldAdjacent Weeds

Lygus populations in second year fields track like Lygus in the adjacent weeds.

InsecticidesInsecticides

Pesticide Chemical Subgroup IRAC # Malathi o n malathi o n organophosphate 1 B Dibrom nale d organophosphate 1 B Diazinon diazin o n organophosphate 1 B Brigade, Bifenture, Athen a

bifenthrin

pyrethroid

3

Danit o l fempropathr in pyrethroid 3

Registered insecticides

• Nerve poisons• Kill nymphs and adults• Problems with resistance• May be valuable as synergists in tank mixes

Registered insecticides

• Nerve poisons• Feeding blocker• Insect growth regulator• Contact poison with little residual activity

1 Treatment dates, May 13, May 20

Lygus Field Evaluation, Watsonville, 2005

Yet to be registered insecticides

• Nerve poison• Nerve poison• Affects insect’s energy metabolism

RimonInsect growth regulator - Chitin synthesis inhibitor

• blocks the production of chitin• insect poisoned cannot make chitin and so cannot molt• Nymphs must molt in order to grow• insect remains in same life stage and eventually dies

First year ‘Albion’Rimon treatment dates: June 11, 2010 June 18, 2010 (Rimon treatments only)Treatments: Untreated Rimon @ 12 oz (2 applications) Rimon @ 12 oz + Dibrom @ 16 oz (2 applications) Bifenture 10DF @ 16 oz (1 application) Assail 30SG @ 6.4 oz + Bifenture @ 16 oz (1 application)Plot size - 6 rows wide x 67’ longFruit > 0.75” were removed prior to treatmentSampled 80 plants per plot for Lygus and fruit damage

Timed to nymphal hatch of first generation

Lygus Control, Watsonville, 2010

Lygus Control - 2010Results

Rimon affects molting

Lygus Control - 2010

Application dates - all treatments 6/11/10 and 2nd Rimon treatment 6/18/10* plus DyneAmic at 0.25% v/v

Mean number of fruit damaged at 27 and 35 days after first treatment, Watsonville, 2010

Second year ‘Albion’ withhigh infestation levelsRimon treatment dates: March 23, 2010 April 5, 2010Treatments: Untreated control Rimon 0.83EC @ 12 oz per acre (2 applications) Diazinon AG500 @ 16 oz per acre (1 application)Plot size - 12 rows wide x 175’ longSampled 80 plants per plot

Timed to first nymphs

Rimon spring spray, Watsonville, 2010

Problem with second year fields - they already have a resident Lygus population from the previous year, and because they have been sprayed the Lygus are more resistant to older insecticides like organophosphates (diazinon, malathion, Dibrom) and pyrethroids (Brigade and Danitol)

Rimon spring spray, Watsonville, 2010

pretreatment

Monitoring for small nymphs to time treatments is very important

Rimon spring spray, Watsonville, 2010• Rimon is best used

early season as it only affects Lygus nymphs and there is more synchronization of the Lygus generations at that time

• Later application is best when tank mixed with another product

• Timing is critical

Pre-treat count = 0.61Lygus per plant; F=0.6700, df=12,36, P=0.7636

Beleaf - Total Lygus (Nymphs + Adults)

* Means are significantly different from control at P<0.05 using Student-t test following arcsine transformation.

Belay is not registered for use on strawberries

Lygus Resistance Monitoring

Santa Maria - 2 sites

Lygus Resistance Monitoring

Watsonville - 2 sites

Blackie Rd.

Salinas

UC Davis - alfalfa

Fruit evaluated at 20 d post treatment were damaged following treatment

Lygus/plant % dama g e Insecticide

1 d before applicati o n

1 d after applicati o n

20 d after applicati o n

@ 20 d after applicati o n

Malathi o n 0.10±0.0 4 0.03±0.0 2 0.70±0.3 3 19.30±3.90 Lanna t e 0.07±0.0 2 0.03±0.0 2 0.53±0.2 8 14.10±1.99 Danit o l 0.15±0.0 7 0 0.06±0.0 6 8.40±2.20 untreate d 0.08±0.0 3 0.09±0.0 7 1.09±0.4 8 29.40±6.67

Effect of insecticide application on total Lygus per plant and % fruit damage (mean±SE of 5 fields), 1996

This study was conducted when Brigade and Danitol were first registered for use on strawberries in 1996.

Lygus Susceptibility - 1996

Lygus bioassaysField collect Lygus adultsAspirate into tubesTreat with field dose of insecticideAdd a treated green bean and determine mortality at 24 hrs

Lygus Resistance

WeedsFirst Year FieldSecond Year Field

Watsonville, July 17, 2008

Lygus collected from -

Danitol

Weeds

First Year

Second Year

10.67 oz in 100 gal2007 sprays - 2 Brigade + 2 Danitol2008 sprays - 2 Danitol

Lygus Resistance

WeedsFirst Year FieldSecond Year Field

Prunedale, July 18, 2008

Lygus collected from -

Danitol

2007 sprays - 1 Brigade + 2 Danitol2008 sprays - 3 Brigade + 1 Danitol

Weeds

First Year

Second Year

10.67 oz in 100 gal

Bug Vacs - 1990

Three row bug vac

Two row bug vac

One row bug vac

Three row bug vac evaluation, 1989

Location - Watsonville, CAVariety - Winter planted 'Selva'Treatments:

• Vacuum weekly• Vacuum twice weekly after reaching

threshold• Bifenthrin applied twice (timed to nymphal

hatch)• Untreated

Three row bug vac evaluation, 1990

Location - Watsonville, CAVariety - Winter planted 'Selva'Treatments:

• Vacuum weekly• Vacuum twice weekly• Vacuum weekly with malathion applied twice

(timed to nymphal hatch)• Malathion applied twice (at nymphal hatch)• Bifenthrin applied twice (at nymphal hatch)• Untreated

Mean (+SD) Lygus per 10 beat sampl e

Treatment Nymphs Adult s Damaged frui t Vacuum weekly 3.9+1.7b 0.5+0.2b 14.7+2.0b Vacuum at threshold

4.9+0.9ab 0.7+0.3ab 18.1+3.5ab

Bifenthrin1 0.4+0 .3c 0.1+0.1b 5.8+0.9c Untreated 6.8+1.9a 1.9+0.6a 23.3+0.3a

Mean (+SD) number of Lygus and number of cat-faced fruit per 50 large green fruit in a field using a three row bug vac, 1989.

Means followed by the same letter do not differ significantly at P<0.05 by Fisher’s Protected LSD following Log (x+1) transformation.1 Brigade applied at 0.1 lb. a.i./acre on May 19, 1989 and July 10, 1989

Mean (+SD) number of Lygus and number of cat-faced fruit per 50 large green fruit in a field using a three row bug vac, 1990.

Means followed by the same letter do not differ significantly at P<0.05 by Fisher’s Protected LSD following Log (x+1) transformation.1 Malathion applied at 1.25 lb. a.i./acre on May 6, 1990 and July 10, 19902 Brigade applied at 0.1 lb. a.i./acre on May 6, 1990 and July 10, 1990

Mean (+SD) Lygus per 10 beat sampl e

Treatment Nymphs Adult s Damaged frui t Vacuum weekly 24.2+5.9b 6.0+1.6ab 17.2+3.3b Vacuum 2X weekly

26.0+3.7b 7.5+1.3a 18.1+3.7b

Vacuum + malathion

20.7+7.6b 3.7+0.9ab 17.5+4.0b

Malathion1 24.7+3.3b 4.3+0.9ab 16.0+2.0b Bifenthrin2 0.8+0.5c 2.0+0.8b 5.3+2.1c Untreated 52.5+18.4a 9.5+2.1a 27.3+3.0a

F r u i t d a m a g e r e d u c t i o n

0

1 0

2 0

3 0

4 0

5 0

6 0

0 5 1 0 1 5 2 0 2 5

A i r f l o w ( k m / h )

Dam

age

red

uct

ion

Percent reduction of cat-faced fruit in plots vacuumed weekly in relation to vacuum machine air flow.

Another look at bug-vacs

Mean ± SE Lygus per 20 plants Date Treatment Small Large Adult 7/20/10 Pre Vacuum 4.65 ± 0.70 0.95 ± 0.22a 3.10 ± 0.33a 7/20/10 Post Vacuum 2.80 ± 0.68 0.25 ± 0.10b 0.55 ± 0.21b 8/12/10 Pre Vacuum 4.35 ± 0.56 0.75 ± 0.18 3.85 ± 0.47a 8/12/10 Post Vacuum 3.80 ± 0.67 0.35 ± 0.13 1.15 ± 0.25b

Watsonville - windspeed, 39 mph; tractor speed 2 mph

Mean ± SE Lygus per 20 plants Date Treatment Small Large Adult 8/12/10 Pre Vacuum 6.15 ± 0.93 0.55 ± 0.15 1.65 ± 0.28a 8/12/10 Post Vacuum 5.15 ± 0.56 0.25 ± 0.12 0.75 ± 0.26b

Salinas - windspeed, 20 mph; tractor speed 2 mph

Measuring bug vac windspeed

Sampled plots before bug vac and in plots further down the same rows after bug vac

Observations?

Another look at bug-vacs, 2010

Mean ± SE Lygus per 20 plants Date Treatment Small Large Adult 7/20/10 Pre Vacuum 4.65 ± 0.70 0.95 ± 0.22a 3.10 ± 0.33a 7/20/10 Post Vacuum 2.80 ± 0.68 0.25 ± 0.10b 0.55 ± 0.21b 8/12/10 Pre Vacuum 4.35 ± 0.56 0.75 ± 0.18 3.85 ± 0.47a 8/12/10 Post Vacuum 3.80 ± 0.67 0.35 ± 0.13 1.15 ± 0.25b

Watsonville - windspeed, 39 mph; tractor speed 2 mph

Mean ± SE Lygus per 20 plants Date Treatment Small Large Adult 8/12/10 Pre Vacuum 6.15 ± 0.93 0.55 ± 0.15 1.65 ± 0.28a 8/12/10 Post Vacuum 5.15 ± 0.56 0.25 ± 0.12 0.75 ± 0.26b

Salinas - windspeed, 20 mph; tractor speed 2 mph

Measuring bug vac windspeed

Sampled plots before bug vac and plots further down the same rows after bug vac

Tend to remove insects that are not so closely associated with the plant and more motile (including larger predators)

Alfalfa strip planted adjacent to strawberries, Monterey Co.

Thanks to Jianlong Bi, 2009

Alfalfa strip planted adjacent to strawberries, Monterey Co.

Lygus Damage - Reflective Mulch

Lygus Damage - Reflective Mulch

Thrips Control - Reflective Mulch

Yields - Reflective Mulch Fruit per plant for our 6 samples

ANOVA statistics F=17.9608; df=2, 8; P=0.0029* Mean significantly different than control at P=0.05 by Students t-test.

*

Lygus ManagementIdentify Lygus and Lygus damageMonitoring - determine when nymphs are present in nearby weeds and in the fieldPrevention - keep Lygus out of the field Eliminate or avoid sources - second year fields harbor Lygus destroy weeds in spring before nymphs become adultsReduce Lygus density mechanically - vacuums? reflective mulch?

Lygus ManagementTreat at the most effective time based on type of chemical Rimon - against early season nymphs; tank mix later season Beleaf - use this after first two applications of Rimon in rotation Pyrethroids - later season and in a tank mixResistance monitoring - bioassaysDon’t overuse the same type of chemical

All About Lygus Management in Strawberry Production

Frank ZalomFrank ZalomDepartment of EntomologyDepartment of Entomology

UC DavisUC Davis

UCCE Strawberry Lygus Bug SeminarWatsonville, CA April 18, 2013