Vegetable Crop Insect Scouting

David Owens, Extension Entomologist, owensd@udel.edu

Peppers
Some reports of spotty but heavy pepper defoliation came in early this week. The most likely culprits are caterpillar pests and Asiatic Garden beetle. Most of the foliage feeding worms and AGB can be controlled with pyrethroids with beet armyworm being the major exception. If peppers are treated with a pyrethroid for defoliators or stink bugs, keep an eye out later in the season for aphids.

Tomatoes
Scout tomatoes for stink bug damage and for spider mites. Stink bug damage will look like light colored or yellow splotches on the fruit surface. If you see damage, consider treating with a bifenthrin containing product or a dinotefuran product (Venom or Scorpion). Be sure to scout for increased spider mite activity whenever using pyrethroids. Spider mite thresholds in tomatoes are 2-4 on an upper canopy terminal leaflet. You may see stipple marks on these higher canopy populations that would not be evident on lower, older leaves.

Potatoes
Scout later potatoes for the next generation of Colorado potato beetle. Scout for potato leafhoppers, particularly in fields that are close to alfalfa. 

Cucurbits
Spider mites continue to be an important threat with hot, dry weather. I am seeing watermelon damage now that I don’t usually see until well after the first melon harvest. Thresholds are approximately half of terminals that show symptoms of mite infestation.

Cucumber beetles are emerging from the soil now. The threshold developed in Indiana is two beetles per plant. Cucumber beetle feeding on rinds tend to have a darker, more textured appearance than that of other rind feeding pests. This next generation is unlikely to spread bacterial wilt. The pathogen needs to be washed from fecal pellets to open plant wounds. This is most likely when beetles heavily aggregate. In summer, they tend to not respond to the same aggregation pheromone.

Squash vine borer continues to be active.

Sweet Corn
Moth survivorship seems to be edging towards greater pyrethroid resistance. Do not rely on this class of chemistry alone for earworm management. Among the Bt varieties, only those containing the Viptera trait (Attribute II, Attribute Plus) provide excellent worm management. These blocks may still need to receive insecticide for thrips and stink bugs.

Fall armyworm is active. Whorl stage infestation thresholds are 15%. Look for window paning on leaves and small holes. Often there will be many plants in a circular shape that are infested with FAW.

Earworm trap activity fluctuated quite a bit this week, with most trap sites reporting more moths than the previous week, which for this time of year is unusual. Please note that blacklight traps have a much different spray schedule, Sites reporting 2+ may want to consider a tighter spray schedule. Trap captures from Thursday are as follows: