David Owens, Extension Entomologist, owensd@udel.edu
Cucurbits
Striped cucumber beetles continue to emerge out of the soil leading to staggered generations and frustration among some folks who are battling them. The most consistent products in recent spray trials have been Assail, Harvanta, and Carbaryl. Lannate is also registered but has little to no residual activity.
Begin looking for aphids in vining cucurbits. August is typically when they begin building up in high number, especially if a field had been treated earlier with pyrethroids.
Squash bug are very active right now. The threshold is 1 egg mass per plant, you may need to hit them twice though, roughly 7-10 days after an application to kill nymphs hatching eggs.
Lima Beans
Scout for tarnished plant bug and stink bug. Thresholds for tarnished plant bug adults (small mottled brown insects about the size of a small finger nail) and nymphs (small, round, green with black spots, about the size of an aphid) is 15 per 50 sweeps. Stink bug thresholds are 7 per 50 sweeps. With stink bug, pyrethroids are recommended. With plant bugs, a couple of other products do a good job including Transform and Beleaf. Of all the bug materials, Beleaf is the only one that will not impact pollinators or beneficials, but it will not control stink bugs.
Sweet Corn
Continue scouting for Fall Armyworm in whorl stage sweet corn. As a reminder, sweet corn thresholds are 15% early and late whorl infestation. New Jersey is reporting elevated fall armyworm activity in the southern and central counties.
Corn earworm moth counts have unexpectedly continued to decrease from last week, with two exceptions where the blacklight traps caught enough moths to indicate a more conservative spray schedule. Generally, I think of the pheromone traps as being our best moth monitoring tool but there are times during the year in which blacklights do a bit of a better job. Trap counts from Thursday are as follows:
| Trap Location | BLT – CEW | Pheromone CEW |
| 3 nights total catch | ||
| Dover | 1 | 12 |
| Harrington | 1 | 27 |
| Milford/Canterbury | 4 | 54 |
| Rising Sun | 1 | 10 |
| Wyoming | 0 | 3 |
| Bridgeville/Redden | 0 | 2 |
| Concord | 3 | 3 |
| Georgetown | 0 | 23 |
| Woodenhawk | 0 | 0 |
| Laurel | 1 | 49 |
| Lewes | — | 4 |
Tomatoes and Eggplant
We will soon be transitioning from stink bugs and spider mites to spider mites and fruitworm. Begin examining fruit for worm holes. Worms are the most important tomato insect pests, in August and September. We have numerous modes of action available. Coverage is very important, use high gallonage.
Continue scouting eggplant for Colorado potato beetle defoliation, Japanese beetle defoliation, and spider mites.