Vegetable Crop Insect Scouting

David Owens, Extension Entomologist;

Sweet Corn
Sweet corn pheromone and blacklight traps are checked twice weekly on Mondays and Thursdays. By Tuesday and Friday morning, data is uploaded to our website: For reference, action thresholds based off of blacklight and pheromone trap can be found here: Moth counts are now very low. This week, we have not been able to test many moths for pyrethroid resistance. The few that we have tested have been mostly susceptible. I suspect this will change later in the season when southern migrants reach our area. Thursday’s trap capture is as follows:

Trap Location BLT – CEW Pheromone CEW
3 nights total catch
Dover 1 0
Harrington 1 1
Milford 0 3
Rising Sun 1 0
Wyoming 1 3
Bridgeville 0 2
Concord 1 2
Georgetown 0 6
Greenwood 0 0
Laurel 1 4
Seaford 1 0
Harbeson 0
Trap Pond 0 0
Lewes 0 7


Be on the lookout for caterpillar pests, in addition to squash bug. Caterpillars similar in appearance to melonworm were observed earlier this week. Although primarily a leaf feeder, they can feed on the surface of fruit. Melonworms are a green color with white stripes, whereas the pickleworm has black spots and is a much more aggressive worm that will tunnel into fruit.

Be on guard against spider mites, caterpillar pests, and first generation cucumber beetles emerging from the soil. Spider mite activity is increasing, and with the hot weather, mite populations can increase up to 10x in a week. If mite webbing is present or thick, as would be the case with an ‘exploded’ mite population (hasn’t been observed yet), a miticide with translaminar or systemic activity should be used. The webbing interferes with contact miticides making effective contact on the mites. Caterpillar pests include many species of moth, including loopers, leaf tiers, possible melonworm, and armyworm (yellow striped and beet). Beet armyworm has been reported in field crops in the area. Later instar worms can feed on rinds. Finally, first generation cucumber beetle adults have just begun emerging from the soil.