David Owens, Extension Entomologist, owensd@udel.edu
Lima Bean
Scout now for tarnished plant bug, corn earworm, and loopers. Thresholds for tarnished plant bug are 15 in 50 sweeps. Fairly specific options include Beleaf, Transform, and Dimethoate if not hand harvesting. Pyrethroids and Lannate are also labeled and will also have activity against earworm and looper. Earworm are flying heavily now. Thresholds are 1 worm per 6 row feet. Pyrethroids and organophosphates can flare up loopers, so be careful to scout for them if a field later on especially if a field is treated with a broad spectrum insecticide.
Pumpkins
Scout for aphids in pumpkins. Heavy infestations can deposit enough honeydew on the fruit for sooty mold to grow, making the pumpkin unsightly. Our most common species in cucurbits is the melon aphid, Aphis gosypii. Aphids can also transmit mosaic virus. We have numerous aphid products available from 5 mode of action classes. Some of them are aphid specific such as Sivanto, Sefina, PQZ, Fulfill and Beleaf, and others have broader worm or beetle activity, such as Harvanta. Reducing pyrethroid applications will help preserve natural enemies in the field and reduce the likelihood or severity of aphid outbreak.
Sweet Corn
Corn earworm trap counts have spiked over the last 7 days. Most trapping locations in our network and University of Maryland’s network are capturing between 20 and 75 per night. Temperatures remain stubbornly high, and moth resistance in pyrethroid vial tests is fairly high. Taken together, along with wet weather, 2-day spray intervals on fresh silking fresh market sweet corn is probably warranted for most locations to be on the conservative side. Also, if you are growing Bt sweet corn, corn earworm is only susceptible to Attribute II sweet corn. Attribute needs to be treated just like a non-Bt sweet corn. Performance sweet corn slows larvae down but does not prevent their damage. At harvest there may be 3rd and 4th instars at the tips as opposed to multiple 6th instars with extensive damage. To be conservative, it would probably be best to treat Performance more like a non-Bt. It may be more forgiving and require slightly less treatment intensity.
Trap counts from Thursday are as follows:
| Trap Location | BLT – CEW | Pheromone CEW |
| 3 nights total catch | ||
| Dover | 10 | 141 |
| Harrington | 0 | 74 |
| Milford | 7 | 166 |
| Rising Sun | 8 | 85 |
| Wyoming | 5 | 68 |
| Bridgeville | 3 | 74 |
| Concord | 3 | 76 |
| Georgetown | 1 | 78 |
| Greenwood | 1 | 67 |
| Laurel | 3 | 130 |
| Seaford | 5 | — |
| Lewes | — | 133 |
| Millsboro | 4 | 19 |
Watermelons
We may still need a rindworm spray this week or next to prevent rind feeding damage by Leps, including earworm. Moths are attracted to flowers, and while earworms love to eat the blossoms, the can also be aggressive on rinds. As a reminder, earworms are less susceptible to pyrethroid applications. Aphids are also flying right now, and although I have not received any reports of significant aphid populations, be sure to keep them in mind. A good sign of aphids is wet spots on the plastic from honeydew secretions.