Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Cole Crops
Cabbage looper and diamondback moth are extremely more active in Georgetown right now than they have since 2020. Bt is a good worm material early on when plants are small, rotate among modes of action. Save broad spectrum materials such as pyrethroids, organophosphates, and Lannate to the end of the season if possible. A couple of years ago we planted cabbage at a large producer’s field, I got excited when diamondback started coming in, we put out our first spray only for parasitoid wasps to destroy every single caterpillar in the field. I got nothing out of the trial and the farmer asked me what my secret recipe was. Be sure to also match up what is present in the field with product selection. Beet armyworm and corn earworm are resistant to pyrethroids. Torac does not get cabbage looper. And Diamondback moths can be a wild card. Harlequin bug can throw a wrench in softer chemistry IPM plan. Good materials for harlequin bugs include pyrethroids and neonics. The advantage of the neonics is that they will pick up aphids.

Cucurbits
Scout for aphids on pumpkins, particularly if pyrethroids have been used for squash bug or squash vine borer control. There are numerous good aphid materials available, including Harvanta, Minecto Pro, and Exirel which should also provide some protection from late worms and borers. Harvanta will also provide decent cucumber beetle protection. Continue scouting for squash vine borer and their coppery colored egg masses.

Tomatoes
Our late tomatoes are about 1/3^rd inch in diameter and with full flowers. This is the stage that is most attractive to corn earworm and worm sprays should be initiated.

Spinach
Beet webworm is active, though numbers do not seem as noticeable at the research station in flowering crops as they were last year. Please note that pyrethroids are not recommended for Hawaiian beet webworm. There are many labeled products for worm management, be sure to match up the right product with other pests that may be present such as aphids.

Sweet Corn
Moth activity over the last few days has been considerably lower, but I expect that will change as warm weather moves back into the region this weekend. Under warm to hot weather conditions, consider moving back onto a 2-day pyrethroid 3-day diamide (Besiege/Eleevest/Vantacor) rotation. Over the last week, we have tested 161 moths in vial tests. Moth survivorship has averaged 50% in cypermethrin (the old standard), 36% with lambda cyhalothrin, 26% with bifenthrin, and 19% with cyfluthrin. This work has been funded by a multi-state USDA SCRI grant no. 2023-51181-41157/project accession no. 1031455. 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 as follows: