David Owens, Extension Entomologist, owensd@udel.edu
Cucurbits
Continue scouting for cucumber beetle, especially in recently planted fields with small plants where defoliation can cause more significant injury. Also scout for melon aphids on any fields that have not been previously treated with a neonicotinoid, either in the drip or as a transplant tray treatment. Occasionally melon aphids build up to such large numbers that they cause leaf cupping and severe stunting, to mention nothing of viruses.
Begin scouting for two spotted spider mites, particularly along field edges that border weedy areas such as field ditches, center pivot points, old cemeteries etc.
Eggplant and Tomato
Be on the lookout for both flea beetle damage on young plants and Colorado potato beetle damage on older plants. Eggplant is particularly susceptible to flea beetle defoliation, fortunately they are fairly easy to manage. Flea beetle thresholds are 2 beetles per plant on small plants <3”, going up to 8 beetles per plant when plants are larger than 6”. Take weather patterns into consideration, as cooler, cloudy weather is going to slow the plants down.
Snap Beans
Scout any snap beans that did not have an insecticide seed treatment and were planted during last week’s cool, overcast weather for signs of seedcorn maggot damage. Compromised plants will be stunted, have small unifoliate leaves, may be missing their unifoliate giving the plant a ‘snake head’ appearance, or plants may be wilting.
Potato
Scout potato for Colorado potato beetle, particularly with the recent warm weather which allows beetles to fly from overwintering sites into new plantings. Thresholds are 1 adult or 4 small larvae per stem. Examine 50 stems throughout the field. Small but heavy infestations may occur near field edges which could be spot treated if necessary.
Begin sweeping for potato leafhopper.