David Owens, Extension Entomologist, owensd@udel.edu
Sweet Corn
Corn earworm trap counts are high. During the first 10 days of silking with temperatures above 82 degrees, a 2 day spray schedule following a pyrethroid and a 3 day spray schedule following a chlorantraniliprole application is advisable, especially at sights with very high moth activity. Next week our temperatures might dip a bit which could allow us to relax a little bit on the 2 day spray interval.
Trap counts can be found at http://agdev.anr.udel.edu/trap/trap.php, and thresholds can be found at: https://www.udel.edu/academics/colleges/canr/cooperative-extension/sustainable-production/pest-management/insect-trapping/silk-stage-sweet-corn/.
Thursday trap counts are below:
| Location | Blacklight Trap | Pheromone Trap |
| Dover | 3 | 210 |
| Harrington | 2 | 159 |
| Milford | 42 | 134 |
| Rising Sun | 20 | 411 |
| Wyoming | 27 | 211 |
| Bridgeville | 1 | 72 |
| Concord | 7 | 40 (1 night) |
| Georgetown | 5 | 42 (1 night) |
| Greenwood | 5 | 130 |
| Laurel | 13 | 136 |
| Lewes | — | 113 |
| Milton | 118 (4 nights) | |
| Whaleyville | — | — |
| Newark | — | 106 (7 nights) |
Cucurbits
Squash bug continues to increase population. Use high pressure to get spray droplets to where adults are hiding under leaves, near the base of the plant, and remember, if you are targeting mostly adults and egg masses are present, a follow-up spray about 7-10 days later may be necessary.
Squash vine borer are active, weekly applications of pyrethroids to the stem should keep them out. Coragen applied for loopers is also effective.
Our second generation of cucumber beetle has begun emerging from the soil. This time of year, we have overlapping generations. It takes larvae about 30 days to complete their life cycle underground. Numbers of adults generally start going up around July 4-10, and we are now squarely in that 30-day window. The two best options for cucumber beetle are Assail (longer residual) and carbaryl (extremely toxic to pollinators, short residual). The next best options may be Lannate (no residual) and Harvanta (decent, great for worms). I do not recommend pyrethroids, but if a pyrethroid were to be used, I suspect Hero at its high rates would probably be the best of that class.
Tomatoes
Brown stink bugs are still active in tomatoes and can be controlled with either a bifenthrin application or a dinotefuran application. Begin incorporating worm materials in a spray program. Earworms and tobacco budworms are actively laying eggs in flowering tomatoes.
Snap Beans and Lima Beans
Scout beans for worms (corn earworm and soybean looper) or consider a treatment if a lot of earworms are observed in the crop. Unlike sweet corn and unlike European corn borer, no threshold is available for timing sprays on either crop for this pest, except a black light threshold that, to be honest, we have not reached or exceeded in years upon years. In lima bean fields, a beat sheet or shaking plants and counting earworms on the ground can be used to estimate populations. Thresholds in lima beans are 1 earworm per 6 row feet. Labeled insecticides include IPM and bee friendly materials such as Avaunt, Vantacor, Coragen, Blackhawk, Bt, and high rates of Intrepid. Of these, Coragen and Vantacor are going to provide the longest residual control.
Stink bugs may also require treatment and complicate matters a bit. Stink bugs are tanks. The best pyrethroid is bifenthrin. Elevest is a chlorantraniliprole and bifenthrin premix which may be handy.