David Owens, Extension Entomologist, owensd@udel.edu
Cole Crops
Diamondback moth and imported cabbageworm are the most common pests of cole crops active right now but keep a sharp eye out for three oddballs: cross striped worm, earworm, and beet armyworm. Earworms are especially damaging as they will go to the growing point and destroy it. Both earworm and beet armyworm are resistant to pyrethroids! Beet armyworm can look superficially similar to imported cabbageworm, but is smooth, not hairy, and has a small black spot right above the second true leg. Cross striped worm has been sporadically active in Georgetown. It lays eggs in masses and multiple larvae can quickly cause issues in younger cole crops.
Sweet Corn
Corn earworm continues to remain quite active, but temperatures are starting to moderate. Above 80-82 °F, earworm eggs take 2 days to hatch, but 3 days at lower temperatures. In theory, we shouldn’t need to have a tighter-than-3 day spray schedule until temperatures rise again. Continue scouting for fall armyworm as the last sweet corn tassels.
Join us Tuesday, September 13 at 4:45 to discuss sweet corn production, economics, and pest management!
Pheromone trap counts are down among all of our monitoring sites, but pay attention to the blacklight traps!!! Most of our black light traps are indicate of a 3-day spray schedule despite some low pheromone trap counts. Occasionally we see this pattern, which is why we like to run both. Thursday trap captures are as follows:
| Trap Location | BLT – CEW | Pheromone CEW |
| 3 nights total catch | ||
| Dover | 7 | 24 |
| Harrington | 1 | 7 |
| Milford | 8 | 16 |
| Rising Sun | 7 | 73 |
| Wyoming | 2 | 21 |
| Bridgeville | 1 | 7 |
| Concord | 10 | 18 |
| Georgetown | — | 4 |
| Greenwood | 2 | 11 |
| Laurel | 6 | 8 |
| Seaford | 2 | — |
Spinach
Scout for pigweed leaf tiers, beet webworm, and beet armyworm. There is a bevy of products available for worm control, including spinosyns, emamectin benzoate, Bt, methoxyfenozide, indoxacarb, and the three diamide insecticides.
Legumes
Continue scouting for stink bugs, corn earworm, and soybean looper. Soybean looper can feed directly on lima bean pods which is different from edamame and soybean. Both soybean looper and corn earworm can be difficult to adequately control. Diamides provide only about 40-60% efficacy on loopers, and pyrethroids are very inconsistent with both but should provide stink bug control.