Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Peppers
Scout peppers for beet armyworm now. Beet armyworm can be a significant defoliator. Eggs are laid in masses, and often a few plants in a row and a few across are damaged most heavily. Look for holes in upper canopy leaves and webbing. The caterpillar is green with a small black spot right above the second pair of true legs (not the abdominal prolegs). Beet armyworm is resistant to pyrethroids but there are a number of other products that will provide good control.

Watermelon
Continue scouting for spider mites on vine leaves. While looking for mites, keep in mind that our next generation of cucumber beetles are due to emerge from the soil very soon. Rindworms of various species are active. In the last couple of days I have been sent pictures of less commonly encountered caterpillars doing a number on the rinds. Look for signs of fresh feeding injury on melon fruit. We have begun catching beet armyworm moths in our pheromone trap, and a report of caterpillars on pigweed came in this week. They can be easily scouted for on pigweeds. We have also seen an uptick in corn earworm moths in pheromone traps this week. They will lay eggs in watermelon and the caterpillars can also be aggressive on the rinds. As a reminder, beet armyworm and corn earworm might not be controlled well with a pyrethroid. Good worm products to consider include diamides, indoxacarb, and spinetoram. Spinetoram and diamides will also control thrips. There is a 2ee recommendation for the use of Verimark on cucumber beetle, and Harvanta has a full section 3 label for them. In a spray trial last year, Harvanta provided some control of cucumber beetles, though not as great as acetamiprid. It did however, result in melons with equal rind protection to acetamiprid. Regarding acetamiprid, there are generics available now.

Sweet Corn
I wrote that we captured a single male fall armyworm in a pheromone trap at the research station last week. This week there have been reports from Cape May, NJ of scattered, below-threshold whorl infestations of FAW. Typically in our area, whorl infestations show up around mid-July. The remnants of Hurricane Elsa may drag up additional moths from the South. If you have whorl infestations greater than 20-30% or tassel-push infestations greater than 15% a treatment is warranted. Scout carefully, often by the time FAW damage is clearly visible, the worms are large and moving out of the corn. If a field is deemed to be above threshold, it would be better not to use a diamide insecticide because we only have a limited amount of the active ingredient that can be used due to label restrictions. We need all of that active ingredient for corn earworm later.

The corn earworm flight has also increased significantly this week at many locations. We have been able to resume vial tests. As of this writing, we completed assays on 30 moths, but have another 40 in vials that will be evaluated after this update. We are seeing signs of decreasing pyrethroid susceptibility, which is a bit earlier than in previous years. Do not rely on pyrethroids alone for earworm management. Premixes with chlorantraniliprole (Besiege and Elevest) are excellent products but only have 3-4 applications with them. Other materials to consider tank-mixing are Lannate and Radiant. Of the pyrethroids, the last two years we have had better efficacy out of beta-cyfluthrin (Baythroid XL) than others evaluated. However, this advantage was not observed in Tom Kuhar’s evaluations last year from the Eastern Shore.

Earworm Trap counts from Thursday are as follows: