David Owens, Extension Entomologist, owensd@udel.edu
Sweet Corn
Scout pre-tassel push sweet corn for fall armyworm now. Processing thresholds are 15% infested whorls early; mid-late whorl stages 30%, and tassel push thresholds are 15%. New Jersey recommends slightly lower whorl and tassel push thresholds for fresh market sweet corn. This worm feeds deep in whorls, use high water volumes. Pyrethroids will not control this worm completely, and in my opinion, we need to reserve chlorantraniliprole (Coragen, Besiege, Elevest) for silk protection vs earworms, unless you have small armyworm starting on husk leaves just prior to silking. If that is the case, you will see windowpaning on the leaves. This is also a good time to consider taking a survey of insect pest issues and management needs and decision making to help entomologists from across the mid-Atlantic and Northeast justify some proposed insect pest management research to refine regional thresholds for sweet corn. Please take a few minutes to provide us feedback!
https://ume.qualtrics.com/jfe/form/SV_9vRh1xHnDp4KEaa
Earworm trap counts are still fairly low, but a little higher than last week. Our next earworm flight will be starting soon. We also have not captured any European corn borer in pheromone traps this year.
| Trap Location | BLT – CEW | Pheromone CEW |
| 3 nights total catch | ||
| Dover | 2 | 39 |
| Harrington | 1 | 42 |
| Milford | 2 | 49 |
| Rising Sun | 1 | 56 |
| Wyoming | 1 | 2 |
| Bridgeville | 0 | 41 |
| Concord | 1 | 39 |
| Georgetown | 1 | 9 |
| Greenwood | 0 | 28 |
| Laurel | 1 | 28 |
| Seaford | 1 | — |
| Lewes | — | 29 |
| Millsboro | 3 | 11 |
Watermelons
Continue scouting for rind feeding injury from cucumber beetle and from various Lepidopteran worms. Cucumber beetles are best controlled by acetamiprid. In recent trials, we have had good results from carbaryl and cyclaniliprole. Carbaryl can flare mites. While mites are active, in most fields we have been at their populations are fairly low. Diamides like Harvanta and Exirel will stop cucumber beetle feeding, but they are very slow to kill cucumber beetles. They are excellent on worms.
Fall Brassicas
Scout seedlings and recent transplants for worms – our entire brassica pest complex is active. Imported cabbageworm, cabbage looper, and yellow striped armyworm can very quickly defoliate small plants. As we head into the fall season, you need to consider what materials and rotations you are going to use in case of diamondback moth.
Cucurbits
Continue scouting for squash bugs, cucumber beetles on smaller plants, and aphids. Pyrethroid sprays for squash bug and squash vine borer can flare up aphids by removing natural enemies.