David Owens, Extension Entomologist, owensd@udel.edu
Sweet Corn
Courtesy of Monday being a holiday, traps were checked on Tuesday and are currently being checked. Next week we will return to a Monday/Thursday trap checking schedule. Be sure to deploy traps adjacent to silking sweet corn for the best idea of what the moth population is doing. Some of our locations are indicating a need to tighten spray intervals to 3 days (based on pheromone or blacklight trap capture). Our typical moderate flight has begun and usually lasts until about the third week of June. This flight sometimes catches people off guard. Trap captures are now being uploaded to our website. You can find them at https://www.udel.edu/academics/colleges/canr/cooperative-extension/sustainable-production/pest-management/insect-trapping/#:~:text=The%20University%20of%20Delaware’s%20Extension,are%20posted%20on%20this%20website.
Tuesday trap captures are as follows (4 nights)
| Location | Pheromone |
| Dover | 18 |
| Wyoming | 5 |
| Magnolia | — |
| Milford | 2 |
| Harrington | 0 |
| Woodenhawk/Greenwood | 28 |
| Bridgeville | 16 |
| Laurel | 57 |
| Concord | 54 (8 in blacklight) |
| Georgetown | 6 |
| Milton | 18 (5 nights) |
| Lewes | 75 (6 nights) |
Cucurbits
Cucumber beetles continue to be very active. Thresholds are 2 beetles per plant. We are getting near the time for bee placement in watermelon. Some insecticides specify a minimum time frame between application and pollinator placement, others do not. (Platinum specifies a minimum of 5 days). The longer the interval the better. If bees are already placed and cucumber beetle populations are high throughout the field, consider using a material like Assail which is far less toxic to honeybees. If bees are about to be placed but have not yet, carbaryl might have a fit.
Any melons that have not received a neonicotinoid treatment need to be scouted for aphids. Look for ant activity on plants and curling and cupping leaves. High aphid populations can stunt plants so severely that their fruiting will be d and they will not be as productive as unaffected plants.
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.
Tomato
Important tomato pests active right now include Colorado potato beetle, flea beetle, and soon, stink bug. Stink bugs usually begin flying in large numbers around the time of small grain harvest, and they can be very damaging.
Asparagus
It did not take long for asparagus beetles to heavily damage untreated ferns in my home garden. Consider a treatment if 10% of plants have adults or if 50% of plants have larvae present.
Snap Bean
Hopefully this is the last week of advising stand counts for seedcorn maggot. Once warm weather returns, seedcorn maggot activity will lessen. Scout for bean leaf beetle. If they were observed previously, they will require treatment during pin-pod stages. They can scar pods.
Potato
Potato leafhopper has been reported in low numbers. Pyrethroids, Organophosphates, Neonics, and a couple of other materials like Portal, Torac, Transform and Sivanto are all labeled. A few of those have CPB activity; only Sivanto and Portal have lower bee toxicity. If a treatment is required, make applications late in the day when pollinator activity lessens.