Insect Updates

Bryan Jensen, UW Department of Entomology and Division of Extension

The following are a few thoughts regarding insects and potential short-term problems.

Potato leafhopper (alfalfa). From what I am hearing, reading and seeing, leafhopper adult number are there and if we get some warmer/drier weather those populations could really increase in a hurry. Time will tell. Start (or continue) to look at both established stands and new seedings. Pay special attention to the new seedings especially because nymphs are hatching now.

Armyworm (corn, wheat, pastures). Significant number of adults of have been noted in black light traps, yard lights and grassy areas. I have received a few reports of small armyworm larvae which suggests scouts need to look very close for damage or it can be easily overlooked. In wheat and pastures, look for feeding damage and larvae on the soil surface. In corn, certainly look for the feeding damage but often plentiful amounts of frass in the whorl is hard to miss.

Cereal leaf beetles (wheat). So far this insect may fall into the curiosity category, but larvae are active, and you may notice some feeding damage (striping) on the upper leaves in small grains. Time will tell how much defoliation or how widespread the problem is. Typically, however, they are controlled by natural enemies.

Cereal leaf beetle feeding on wheat

Seedcorn Maggot (corn and soybean). Now would be a good time to monitor stands to determine if seedcorn maggots may have had an impact on germination and emergence. We had (in southern WI) a peak flight of adults a few weeks back impact on stands can be noticed now. If seedcorn maggots impacted plant populations I would expect to see above ground symptoms not just skips within the row. In soybean those “other” symptoms would include “snakeheads” (which is a symptom we use to describe when the cotyledons are chewed off and only the hypocotyl exists) and feeding damage or scarring to cotyledons. In both corn I would also expect to see holes in the cotyledons as well as holes in the unifoliate leaves of soybean.

European corn borer (corn). Parts of southern Wisconsin are entering the period when damage may be noticed in corn that is taller than 18 inches extended leaf height. I don’t expect many problems again this year, but those very early planted fields may be attractive to the adults.