Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Sweet Corn
This will be the hardest crop to keep clean that we will have all year. Pheromone and blacklight trap captures continue to increase. We have not experienced such large blacklight trap counts in a while. Spray interval thresholds can be found at our website: https://www.udel.edu/academics/colleges/canr/cooperative-extension/sustainable-production/pest-management/insect-trapping/silk-stage-sweet-corn/. Several of these locations are exceeding the 38 moths, in 7 days blacklight interval for indicating a 2-day spray schedule. Pheromone trap counts are extremely high right now. There are a few locations where counts are low, one is a trap next to silking sweet corn but be advised that silking sweet corn is the most attractive to moths and we do not move our traps. If you have a trap or you know a consultant has a trap next to silking sweet corn and is closer to your location, use the more conservative spray interval. Vial test results from earlier this month resulted in 38% survivorship in cypermethrin. We are starting to test individual pyrethroid active ingredients, and the trend that we have seen is close to the last several years’ spray trials which suggested that among pyrethroids, Hero (high rate)> Baythroid >= Brigade >= Warrior. If using Elevest, Hero or Brigade (or other generic bifenthrin) be aware that there are active ingredient restrictions on bifenthrin and that only a couple of applications can be made. Even if you treat with a high rate, tank mixtures with another active ingredient such as methomyl (ex Lannate), spinosad (Blackhawk), or spinetoram (ex-Radiant and Intrepid Edge) is recommended. Besiege or Elevest are premixes with chlorantraniliprole and are our most effective worm materials. Looking back on 14 years’ worth of spray trials, there have been 6 years in which Besiege, or its equivalent was applied three times in a row versus alternating treatments. In 2 of those years, up front application was slightly better, in 2 years alternation was better, and in 2 years they were equivalent.

Thursday trap counts are as follows:

Peppers
Beet armyworm activity has been increasing. Scout for defoliation and caterpillars in webbing near the plant terminals. If a treatment is warranted, please note that pyrethroids will not control them.

Cucurbits
Beet armyworm is active in fields. Scout pigweeds and pay attention to terminal areas. Beet armyworm makes webbing and multiple caterpillars will be found feeding in the leaf webbing. Treatment before they move off pigweed and onto rinds may be advisable. Our best beet armyworm product is Harvanta as it also has cucumber beetle activity.

Pumpkins
A report came in from Pennsylvania this week of possible pickleworm damage to pumpkins in Pennsylvania. Scout fruit for signs of caterpillar entry holes on the rinds. Moths are triangular in shape with white wings bordered by brown. If pickleworm activity is detected, begin weekly insecticide application. There are many labeled products, and all should provide good control.

Cole Crops
Whiteflies causing significant damage to backyard vegetable garden cabbage and Brussels sprouts were reported this week. We have been seeing high whitefly activity in other crops in Sussex and last year New Jersey reported significant whitefly injury to cole crops. Whiteflies should be controllable with neonicotinoid insecticides which will also control aphids and harlequin bugs, cyantraniliprole (Exirel) which should also do a good job on the worm complex and aphids, Rimon (novaluron), effective on small populations and will do a good job on small worms), and a few much more specific insecticides like Movento, Versys, PQZ, Knack, Sivanto and Closer.

Be sure to identify your green worm complex. Diamondback moth is favored by the dry weather we have had recently. Caterpillars are small, bumpy, and green; wriggle violently, and hold their anal prolegs out in a V shape. Imported cabbageworm is smooth and velvety. Cabbage looper only has 2 abdominal prolegs and makes large looping movements. The abdomen is wider than the head and thoracic region. Beet armyworm has a small black spot above the 2^nd pair of legs behind the head. Pay special attention for this one, particularly if pigweeds are present, as they are resistant to pyrethroids. Don’t be like Bob and ask me why Warrior didn’t kill the ‘cabbageworm’ in his field.