David Owens, Extension Entomologist, owensd@udel.edu
Spinach and Beets
Beet webworm activity is unusually high this year. In Georgetown, they have stripped a lot of foliage off pigweeds. In addition, beet armyworm activity is also getting into oddball places, just like earworm will this time of year. Pyrethroids are not recommended for beet armyworm, and I have heard that they are not reliable against beet webworm. We saw an earlier uptick in green peach aphid in August and the first part of September, but recent rains seem to have helped suppress them. If you need to control both aphids and worms, Durivo, Exirel, Verimark, Harvanta, and Torac are all effective on both.
Cole Crops
All major worm pests are active, imported cabbageworm, diamondback moth, cabbage looper, and cross striped worm. Cross striped worm thresholds are 5% infested plants. They can cause heavy damage to a developing cabbage head. For the other three, it is not uncommon for parasitoid wasps to destroy large numbers of them in all life stages, including eggs. Thus, preserve your beneficials as much as possible! Do not use pyrethroids or organophosphates until the very end of the season. Even the spinosyns such as Radiant can be a bit hard on them. Beet armyworm and corn earworm both get into cole crops as well, and when they do, they destroy the growing points resulting in hollow, head-less cabbage. For these, it is probably well to use the threshold for cross striped worms. Once heading begins, thresholds decrease to 5% regardless of worm species.
Tomatoes
Continue scouting late tomatoes and treating accordingly. Although stink bugs tend to be an earlier summer pest, recent tomato harvesting in Georgetown has turned up quite a few damaged tomatoes and brown stink bug nymphs. Corn earworm is still active and protective measures for worms are highly recommended.
Legumes
Continue scouting for earworm and loopers. Recent nighttime temperatures in the 50’s tend to result in sickly, unthrifty loopers, but remember, in lima beans they can damage pods unlike other legume vegetables.