Wisconsin Field Crop Insect Updates

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


I have had a few more calls coming in since last week’s article. Keep looking. Especially in corn planted into a grass cover crop. I would expect this generation will be finishing soon. High populations during the current generation does not mean a significant problem with the next generation. Keep scouting.


Yes, there are some out there but with good growing conditions I think corn will outgrow most of the injury. Hot spots may exist in soybean which could reduce stands in very late plantings.

Japanese Beetle

No significant reports but………….be patient. The take home message is to assess % defoliation on a “whole plant” basis. Not just the top nodes on soybean. An unneeded insecticide application could flare soybean aphids and two-spotted spider mites.

Potato leafhopper (pictured)

Sweep alfalfa if you haven’t. It is early to predict impact on established stands. However, damage to new seedings is always a concern because of the longer period between harvest.

Soybean Gall Midge

Soybean gall midge has not been found in Wisconsin. However, states with this insect pest have indicated emergence of the overwintering adults. Keep this insect in the back of your mind if you find dead or dying plants on field borders and can’t come up with another cause. Please let me know ASAP if you see damage and find the clear to orange colored maggots at the base of the soybean plant. More information will be coming in the Wisconsin Crop Manager to help with field diagnosis.

European corn borer

DATCP indicates populations are at an all time low. Occasionally I hear of a few corn fields with economic injury. If you are in an area which has had injury in previous years make sure you look at susceptible corn fields (non-Bt hybrids with >18 inches extended leaf height). That isn’t a license to ignore traited hybrids. Resistance has not been documented in Wisconsin. Is it a matter of time?

Soybean Aphid

DATCP has found soybean aphids at low numbers this spring. Although populations have been low in previous growing seasons this insect is capable of rapid population increase. It is not too early to do some spot-checking.