David Owens, Extension Entomologist, owensd@udel.edu
Cucurbits
With warmer weather in the forecast, begin scouting for striped cucumber beetle. They usually begin rolling into fields between May 14 and May 21. It is important to look at multiple locations because males release aggregation pheromones that concentrate adults in relatively small areas of fields. Pay attention to transplant wagons as well. A tray drench can be used to kill beetles infesting transplant wagons, but will not provide long residual control once planted. Tray drenches can be used to manage aphid populations.
Snap Beans
Be sure to have an insecticide seed treatment on snap beans being planted in cool, wet soil. Although warmer weather will help get snap beans out of the ground faster, seedcorn maggot activity is high right now. Damage often appears as a plant with expanded cotyledons but a damaged or dead growing point, swollen stems underground, and severe stunting.
Greenhouse Vegetables
Vegetables grown in greenhouses may face injury from aphids, thrips, spider mites, and occasionally other insect pests. The Commercial Vegetable Production Guide has a section (E) that lists insecticides labeled for greenhouse use.
Cole Crops
Diamondback moth activity continues. Scout plants carefully and identify species present. Diamondback moth will have a bit of a bumpy appearance, hold their anal prolegs in a V-pattern, and wriggle violently when prodded. Imported cabbageworm early instars are yellow changing to a fuzzy green. They tend to rest on upper leaf surfaces near the midveins and grow to a sizeable caterpillar. Cole crops with just imported cabbageworm can be treated with a wide range of insecticides, while diamondback moth tends to be resistant to pyrethroids. Remember, there are a lot of natural enemies of all the worm complex. Thus, preserving those natural enemies by limiting use of pyrethroids and other broad spectrum insecticide modes of action is very important for long term worm management.