Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Sweet Corn
Much of the sweet corn crop is in, what is left though still faces high pressure. For the most part, daytime temperatures are forecast to be in the low 80s to upper 70s, thus, adjusting spray schedules for temperature is not necessary. Thursday trap results are as follows:

Cole Crops
Continue scouting all cole crops. All cabbage pests are active, including some oddballs such as beet armyworm and the webworm complex, particularly in fields with a lot of pigweed. Cabbage looper is very active. Recent heavy rains should help suppress diamondback moth, however their populations were ticking upwards. Thresholds for early stage plants prior to cupping or head formation are 20% infested plants. Remember to rotate modes of action from one spray to another and to rotate modes of action out every 30 days. Good coverage is essential, and in many cases, use of an adjuvant will help improve control on the waxy leaves. Do not use binder or sticker adjuvants when using diamides or Radiant, these products try to get across the leaf membrane into the tissue, while stickers try to keep the product on the surface.

Harlequin bugs have also been unusually active, especially in locales where cole crops were either present throughout the summer or an earlier crop was left in the field instead of removed. Harlequin bugs are tanks, the only products that do a good job on them are pyrethroids and neonicotinoids. The neonics by themselves have poor efficacy on worm pests. Pyrethroids generally do a great job at controlling imported cabbageworm and cabbage looper, but diamondback moth, beet armyworm and corn earworm, if present, can be much more difficult to kill. Besiege is labeled on all crops but kale; pay attention to your rotations and to the amount of chlorantraniliprole applied.

In Georgetown, aphids have been more active than last year, as have whitefly. Last year whiteflies were present through the month of September and then declined, and did not cause any injury to the plants. In addition to numerous excellent aphicides (Group 4A, C, and D, group 9B, 23, and 29), Exirel, a diamide insecticide, is also labeled for aphids and whiteflies and is an excellent worm product. Orthene is labeled for Brussels sprouts and cauliflower and does a good job on worms. Torac is labeled and has worm activity, but not for cabbage looper. Rimon has worm activity and is also active on whiteflies but not aphids. Movento is good on aphids and whiteflies, and has some worm activity but should be supplemented.

Lima Beans
Soybean looper activity in southern Delaware is increasing. Soybean looper will attack and destroy immature pods. Diamides (Coragen, Besiege) will take out between half and ¾ of the loopers. Intrepid is labeled but will not be effective on corn earworm. What is interesting is that Intrepid Edge is not labeled for lima beans although both Intrepid and Radiant are. Lannate is not labeled for looper, but is for the other worm pests, pre harvest intervals are 1 to 3 days, depending on rates. The Vegetable Production Guide suggests a threshold of 1 worm per 6 ft. If using a sweep net, this probably will come out to about 1.5 per 15 sweeps.

Spinach
Beet webworm is active. Up until now it has largely been feeding on pigweeds. Spinach is in the same plant family and moths find it just as attractive for oviposition. The same goes for beet armyworm. Bt products can be used if worms are small. Keep in mind they have very short residual activity. Radiant, Proclaim, Avaunt, Intrepid and diamides like Coragen, Exirel and Harvanta are all labeled for the worm complex. Intrepid is a growth regulator and should target small worms. Diamides will cause rapid feeding cessation. Diamides and Radiant may also help with leafminers, while the diamides (except Coragen) are also labeled for aphids.