David Owens, Extension Entomologist, owensd@udel.edu
Cucurbits
Cucumber beetles continue to be very active. Thresholds are 2 beetles per plant. As a general reminder, we have not seen good efficacy from pyrethroids from our MD/DE beetle populations.
On summer squash, begin scouting for squash bug. Thresholds are to spray once an average of 1 egg mass per plant is found, waiting until eggs begin hatching. This may require a follow up spray 7-10 days later as eggs are impervious to insecticide.
Potatoes
Begin scouting for potato leaf hopper. This pest usually makes its way to our area on southern wind and storm events by the beginning of June. Thresholds are 1 adult or nymph per 10 leaves. Nymphs are small, yellow-green and move sideways. Adults are small, have a glossy whitish green wing and take flight quickly if disturbed. Sweep nets can be used to verify their presence but thresholds are based on sampling leaves. Potatoes treated with neonicotinoids at planting may still be protected from leafhopper. Neonics and other group 4 insecticides (all of which have long residual activity) Pyrethroids, carbamates, and Torac and Portal are labeled for leafhopper.
Potato fields in bloom right now may benefit from a wireworm application of Movento. Movento moves down into the root system and will suppress wireworms. I generally do not recommend products that only have suppression on the label, but in this case, we have included it in the Vegetable recommendation guide. Tom Kuhar has seen good results from this application, and at this point, there is nothing else that can be done to mitigate wireworm short of harvesting as early and timely as possible (which doesn’t always happen). It also has nematode suppression on its label.
Sweet Corn
Corn earworm trap counts are beginning to increase. So far, traps capturing moths are indicating a 4 to maybe 5-day spray interval, especially with cool wet weather. Over the last few years, I have noticed higher sap beetle activity in early sweet corn as well. It may be beneficial to consider including a sap beetle material around silk wilt, about 10-14 days after silking.
Traps are being checked today. Trap counts from Tuesday (5 nights) are as follows:
| Location | Blacklight | Pheromone |
| Dover | 0 | 4 |
| Wyoming | 0 | 2 |
| Magnolia | 0 | 10 |
| Milford | 0 | 0 |
| Harrington | 0 | 0 |
| Woodenhawk/Greenwood | 0 | 0 |
| Bridgeville | 0 | 0 |
| Laurel | 61 | 0 |
| Concord | 21 | 0 |
| Georgetown | 13 | 0 |
Legumes
Pay close attention to germinating stands for any legumes planted during the past week. Wednesday and Thursday weather were perfect for seedcorn maggot, and while it would be a bit late in the month for stand loss to occur, it still can. Begin also scouting for bean leaf beetle. Thresholds are pretty high for them. If not treated now, snap beans that have them will need to be treated once pin pods are present.