Field Crop Insect Updates

Bryan Jensen, UW-Madison Dept. of Entomology and Integrated Pest Management Program

Potato leafhoppers. By most reports are still going strong. Continue to sweep until there is a consistent drop in populations over a couple weeks. Be especially concerned with new seedings. When will leafhopper populations decline? It is very hard to predict. Usually by mid August, sometimes not until early September.

Armyworms. There have been few reports regarding the summer generation. But now is the time when significant damage can be spotted in corn.

Corn Rootworm Adults. Monitor late planted fields for silk clipping. Adults are mobile and will move around the landscape looking for pollinating fields. We will soon approach the best time to scout beetles to determine the need for and/or the most appropriate control decision in next year’s corn.

Two-spotted spider mites. Droughty areas should be monitored for damage and signs of live mites.

Soybean aphids. Scout. We still have time for populations to increase but economic control decisions get more difficult.

Soybean Defoliators. Grasshoppers have been reported in some areas. Dry weather tends to increase grasshopper populations both for the current year and the following year. Especially when populations peak late season. Japanese beetles are still active but potential for damage is diminished as the growing season progress. Other caterpillars have been reported but remember the economic threshold for defoliating insect is 20% defoliation. Those decisions should be made based on the leaf area of the whole plant, not just the upper leaves.