David Owens, Extension Entomologist, owensd@udel.edu
Sweet Corn
Trap captures continue declining, and field corn is beginning to silk. Although black light traps continue to indicate elevated activity at most locations, pheromone trap capture is very low.
| Location | Blacklight trap capture | Pheromone Trap Capture |
| Dover | 9 | 23 |
| Wyoming | 5 | 9 |
| Magnolia | 35 | 20 |
| Milford | 11 | 9 |
| Harrington | 4 | 6 |
| Woodenhawk | 1 | 7 |
| Bridgeville | 4 | 7 |
| Concord | 8 | 2 |
| Georgetown | 0 | 6 |
| Laurel | 8 | 12 |
| Delmar | 27 | |
| Lewes | 31 | |
| Milton | 4 | |
| Whaleyville, MD | 23 |
Last week and this week we captured low numbers of male fall armyworm in a trap in Lewes. Historically, I usually don’t start seeing fall armyworm signs until after July 4th but be cautious. Armyworms consume 80% of all that they are going to eat during the last 3 days of their larval development. It is also this time that they would be very deep in whorls and difficult to reach with any insecticide. The time to treat for them is when they are small. Look for windowpaning lesions extending down into the whorl. Thresholds for mid-whorl stage plants are 30%. I do not recommend using a Besiege or Elevest or Vantacor application on fall armyworm because we need all that active ingredient for silk protection. Instead, consider Intrepid Edge or Avaunt. Intrepid Edge can be used as a tank mix partner with pyrethroids for silk protection. Lannate or a Lannate pyrethroid mix can also be a good option if plants are small and worms are small and exposed.
Cucurbits
In addition to spider mites, squash bug and squash vine borer are very active right now. The good news is that pyrethroids will get both, the bad news is pyrethroids may also flare up aphids a few weeks after application. For squash bug, look for the coppery colored egg masses laid especially on the underside of leaves and clustered around veins. The threshold is 1 mass per plant and to wait until eggs begin hatching, but this may require two applications.
Potatoes
Potato leafhopper is very active right now, but potatoes are also approaching senescence. Leafhopper thresholds are 1 adult per sweep or 1 nymph per 10 leaves. If you feel that a leafhopper spray is needed, they are very susceptible to pyrethroids, neonics, and a couple of other materials. Portal is labeled, but I wouldn’t use it unless mites were your primary pest. Torac is labeled, but it’s probably best used when Colorado potato beetle is more of a threat. There are a few other products labeled in the vegetable guide.
