Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Cucurbits
Striped cucumber beetles continue to roll into fields. We are beginning another pyrethroid resistance monitoring effort this year and need beetles from all over Delmarva. If you have a location in which the entomology lab could collect 200-300 beetles fairly easily from Virginia, Maryland, or Delaware, please let us know!

The most common method for striped cucumber beetle control is a drip chemigation treatment of a neonicotinoid. Over the years, we have observed a little bit longer residual from thiamethoxam as compared to imidacloprid, but have not tested clothianidin or dinotefuran. Make sure that you are applying the proper amount per 1,000 ft of drip tape. Be especially aggressive on cantaloupe, as they are susceptible to bacterial wilt. Do NOT rely on pyrethroids in our area.

Spider mites are beginning to show up. Scout field edges and any other in-field obstacle such as a pivot point, irrigation gun, ditch, old tree, or cemetery. This early, if spider mites begin to show up, they will most likely be in small spots near the edge and could be spot treated if necessary.

Cole Crops
Continue scouting for worms – imported cabbageworm and diamondback moth are the most active right now. For diamondback moth, look for windowpaning on the leaves where the larvae have chewed the bottom surface close, but not quite all the way through. Aphids are active, and harlequin bugs may begin moving into fields. Remember, thresholds decrease as we approach heading.

Eggplant and Tomato
Flea beetles and Colorado potato beetles are the primary pests of seedling eggplant. 1-2 flea beetles per plant can result in significant defoliation and set the seedling back. Their feeding results in small, round shot holes. The most common flea beetles on eggplant right now are small bluish beetles that are extremely active.

Different species of flea beetles tend to affect tomato. Colorado potato beetle may also feed and reproduce on tomato. They will even scar up developing fruit. With small grains beginning to senesce, be sure to scout for thrips on tomato.

Potato
Continue scouting for Colorado potato beetle, their egg masses, and larvae. Thresholds are 1 adult per stem or 4 small larva per stem or 10% defoliation.

Legumes
Scout for signs of stand loss due to seedcorn maggot. Affected plants will have etched cotyledons, the plumule may have been killed resulting in cotyledons without unifoliates, wilting plants, and swollen stems underground.

Scout for bean leaf beetle and consider a treatment if 1-2 beetles per plant or 20% defoliation is observed.

Sweet Corn
Many thanks to Victoria Smith for maintaining traps this year. Earworm catches right now are low, but not non-existent. Trap counts typically rise until the 2^nd or 3^rd week in June.

Trap counts from Tuesday to Thursday are as follows: