David Owens, Extension Entomologist, owensd@udel.edu
Asparagus
Continue scouting for asparagus beetle oviposition. Michigan State recommends; 5% of spears with adults and 2% of spears with eggs. Labeled materials include carbaryl, (pay attention to rates pre-harvest) malathion, PyGanic (OMRI) and permethrin. Check multiple locations in the field, adults tend to be more heavily concentrated around field edges.
Snap Bean
Bean leaf beetle are active. Scout for defoliation to seedlings and keep note of any fields that have activity, even if below threshold now. Bean leaf beetle feeding will look like circular to rectangular holes in leaves. Adults exhibit quite a bit of color variation, with a light tan, orange, and red being the most common. They may or may not have black spots on the wings but always have a black triangular mark where the wings join together and just behind the prothorax. If bean leaf beetle remain active at bloom, consider treating for them, they can scar pods. They are very susceptible to pyrethroids.
Cucurbits
Continue scouting for aphids and mites on greenhouse transplants and plants on wagons waiting to be placed. Also begin scouting for cucumber beetles. They typically show up around the middle of May, but recent unusually warm weather may have gotten them out a little bit early. Pay special attention to early season cantaloupe transplants, as this crop is susceptible to bacterial wilt and a lower threshold than 2 per plant is justified.
Cole Crops
Continue scouting for worm infestation among young transplants. Seedlings and early transplant thresholds are 20%, this rises to 30% as the plants grow. Be careful to identify species present, diamondback moth larvae are small, tend to windowpane, have a bumpy appearance, hold their back prolegs out in a V shape, and wriggle violently when disturbed. Imported cabbageworm is a fuzzy green, just hatched larvae tend to be a bit yellower. Cabbage looper loop. While plants are small, this is good time to use Bt. If using Bt, coverage is especially important. Aziawai strains tend to be a bit more effective than kurstaki strains.
Also, harlequin bugs and flea beetles are active and need to be monitored. Flea beetles can be controlled with diamides and spinosyns which also provide very good worm control.
Peas
It may be worth examining peas for aphid outbreaks. Such outbreaks are not too common, but with the dry weather we have had, they will put additional stress on the crop. Aphids are controlled by wasps and by fungal pathogens, and we haven’t had the weather for fungal pathogens. This week the entomology program swept many alfalfa fields and noted significant pea aphid populations.