Vegetable Crop Insects – May 4, 2012

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Melons
As soon as plants are set in the field, be sure to scout for aphids, cucumber beetles, and spider mites. The first cucumber beetles have been observed and with the predicted warmer weather for the end of week we could see an increase in activity. Since beetles can continue to re-infest fields as well as hide under the plastic, multiple applications are often needed to achieve control.

Potatoes
Low levels of the first emerged adults continue to be found in fields where an at planting insecticide was not used. A treatment should not be needed for adults until you find 25 beetles per 50 plants and defoliation has reached the 10% level.

Snap Beans
Be sure to sample all seedling stage fields for leafhopper and thrips activity. The thrips threshold is 5-6 per leaflet and the leafhopper threshold is 5 per sweep. If both insects are present, the threshold for each should be reduced by one third.

Sweet Corn
Be sure to scout emerged fields for cutworms and flea beetles. As a general guideline, treatments should be applied for cutworms if you find 3% cut plants or 10% leaf feeding. In order to get an accurate estimate of flea beetle populations, fields should be scouted mid-day when beetles are active. A treatment will be needed if 5% of the plants are infested with beetles. In fields that were planted under plastic, begin to scout for corn borers as soon as the plastic is removed.

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