Field Crops Insect Pest Updates

David Owens, Extension EntomologyUD Carvel REC, 16483 County Seat Highway, Georgetown

owensd@udel.edu(302) 698-7125@OhBuggers

Excessive Rain is Good For Something…

Critical Crop Protection Periods

• Emergence• Mid-season canopy development• Reproductive stages

• Corn – Emergence and R-stage corn• Sorghum – R-stage sorghum• Soybean – Emergence, Mid-season, R-stage

2019 Corn Preparation

• Sample wireworms and white grubs, especially in weedy fields

• Wire trap – 25% SCM, 10% WW, 5% WG, 5% Unknown

• Solar bait trap: Purdue extension video: https://www.youtube.com/watch?v=t3VUKw_TfKc

• Digging for grubs: 8 inch square 6 inches deep in fall or spring

• 1 whitegrub/ sample in spring. 1.6 in fall.

What’s In The Corn Seed?

• Handy Bt Trait Table• ECB regional suppression• CEW not an issue in timely corn;

only Vip3A or a triple pyramid • CRW – not needed for rotated

corn• BCW – Vip3A, Cry1F

• https://cropwatch.unl.edu/2018/which-bt-traits-do-you-need-buy

ECB Still Present, Be Vigilant

Late Planted CEW in Corn

Late Planted Field Corn

• Agrisure 3122 – Cry1ab and Cry1F, mCry3A and mCrya34/35Ab1• Besiege 10 oz 5 DAS

05

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Besiege UTC

Mean # Clean Ears and Worms Per 25# Clean Ears # of worms

*

Sorghum – R-stage period

• 1 larva per head = 5% yield loss ~ $12.60 assuming 80 bu/a, $3.15/bu(https://extension2.missouri.edu/g7110)

• Spots of sorghum in SW Delaware exceeded threshold

Sorghum Aphids

• Examined 4 sorghum fields for white sugarcane aphid, found aphids in 2 fields. • Sorghum acreage has declined in VA and throughout the country• Evolving picture. Is it going to cause problems here?

John C. French Sr., Retired, Universities:Auburn, GA, Clemson and U of MO, Bugwood.org

Yellow Sugarcane Aphid, Sipha flava. Hairy body

White Sugarcane Aphid, Melanaphis sachari.Not hairy; short, black cornicles, black feet

Bottom line with sorghum: It’s not a ‘plant and forget’ crop, particularly when flowering – milk corresponds to earworm flight. Be on the lookout of aphids. If they are going to cause problems, they will be easy to find

Soybean Survey

• Top Pests: Bean Leaf Beetle, Soybean Looper, Corn Earworm, Stink Bugs• Critical Times For Scouting: Emergence, mid-season canopy, R1-R6

• Between 2 – 5% yield impact, 50% automatic insecticides

Stand Establishment

A Highly Unusual Stand Reducer

A Potential Stand Reducer

Seedling threshold 40% with 2-3 beetles/plant

Soybean Defoliation

• Full season bean threshold: 40% pre bloom, 15-20% R1-R6, 35+% R6• Double crop fields with small canopies cannot tolerate nearly as

much.

How Much Does Vegetative Defoliation Influence Yield?– Angus Catchot, Mississippi State

V3 D

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V6 Defoliation0 33% 66% 100%

0 100% 97% 96% 77%33% 105% 93% 88% 83%66% 100% 95% 101% 92%

100% 86% 75% 79% 75%

Yield (% of UTC)

Rain Rain Go Away – uh oh.• Cant neglect field interiors, but – most mites show up on edges first• Cool temperatures, high humidity, heavy dew in field crops can lead

to mite declines – August crash, but – collected large numbers out of a corn maze in October

July 19

R-stage Soybean

Impact of Drought – Corn Earworm• Fields in SW Delaware experienced heavy (for us) corn earworm

pressure• Non-irrigated fields, dry corners, double crop fields at greatest risk.

Irrigated fields less pressure

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https://www.ces.ncsu.edu/wp-content/uploads/2017/08/CEW-calculator-v0.006.html

CEW Resistance

• Management becoming increasingly frustrating

• 20-40% survivorship in DE worms 2018

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Mean % H. zea moth survival, 5 µg cypermethrin—2003-2018

137 moths treated, 126 untreated

21.40%26.80%

32.30%

68.40%

42.80%

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10.00%

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50.00%

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June July August September Overall

Mean % H. zea moth survival, 5 µg cypermethrin—DE 2018

CEW in Soybean• Drought/nematode stressed, open canopy, R1-R4/5 fields or portions

of fields most attractive

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Baythroid XL@ 2.8

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Data from Dr. Sally Taylor, Virginia Tech Tidewater AREC, Suffolk

CEW in Soybean

• Pyrethroid alone may or may not be satisfactory. • Natural enemy reduction following pyrethroids

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Sussex worms per 100 sweeps

CEW

Loopers

Texas A&M Horticulture

Soybean Looper vs Green Cloverworm• GCW – very active worm, present June – September,

easy to kill• Count prolegs – 3 abdominal vs 2. Loopers present

August – October, difficult to kill A. Herbert - Newsletter

Video showing green cloverwormviolent wiggling when prodded. Soybean looper does not respond the same way. Courtesy of Nick Seiter, Univ. Illinois

Loopers in Soybean

• Grasshopper + Looper• Paired 2 ‘heavy defoliation’ with ‘lighter

defol.’• 29 vs 40 bu/a

Loopers in Soybean

• Estimate entire canopy defol. (BLB)

• Loopers tend to start from the lower canopy

• What stage are the beans?• What stage are the worms?

• Eat 80% in the last 3 days

Soybean Looper Damage 2010

42. 9 Bu/ A 9.8 Bu/ A

•Grower challenged consultant’s recommendation to treat•Beans were early R5•Left the strip out to show that worms wouldn’t hurt his yield…

Photo: Gus Lorenz/University of Arkansas

Delaware in 2010

Cory Whaley

Soybean late-season: soybean loopers

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30-Aug 8-Sep

2017 2018

Treated 24-Aug

Soybean Summary

• Scouting is key, especially after a previous pyrethroid• Coverage is key• ID is key• Judicious insecticide selection is key

Calling For Dove Plots

Insecticide Update

• As of right now, EPA is appealing 9th Circuit panel decision on Lorsban removal to the full bench. We expect Lorsban to be available through the 2019 season

• Torac (tolfenpyrad, G21a) now has supplemental labels for brassicas, fruiting vegetables, cucurbits, potatoes. Broad spectrum contact only.

• Vydate usage restrictions proposed lengthening REI’s to 3 days for all cucurbits, 4 days for potato, and 5 days for onion. Maximum application rates would be 1 lba.i./acre. Remove celery, eggplant, peanut, tobacco, tomato, and orchard uses

• Inscalis (Afidopyropen) Sefina and Versys now labeled on tree fruit, vegetable fruit, and soybean. Translaminar aphid, scale and whitefly product.

• Neonic interim decisions to be released this quarter• Pyrethroid interim decisions in Q2

Acknowledgements

• Sussex County Council• Delaware Soybean Board – insect survey• Bill Cissel, Joe Deidesheimer, Samantha Cotton,

Kevin Troyer, Joe Wheeler, Carolina May, AgostinaArmondo

• Area Consultants