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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
Monitoring…..
Second Year FieldFirst Year FieldAdjacent Weeds
Lygus populations in second year fields track like Lygus in the adjacent weeds.
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
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 - 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
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
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)
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