Agronomic Crop Insect Scouting

David Owens, Extension Entomologist,

Field Corn
Continue scouting for Japanese beetle silk clipping and for pollination progress. If beetles have clipped silks back to less than a half inch and corn is less than 50% pollinated, a spray may be needed. However, it usually takes an extremely high number of beetles to do this. Beetles will concentrate along pivot tracks and the edges of fields, as will stink bug.

Recent rains over much of the state have helped the bug situation in soybeans. Continue scouting for spider mites. While rain helps plants compensate for mite injury, rain is not a cure for mites. Now that full season beans are flowering, defoliation thresholds decrease to 15-20% defoliation. Worms, Japanese beetles, and bean leaf beetles are all active right now. The good news is that, should a spray be necessary, all of the current active defoliators are susceptible to pyrethroids. But pay careful attention to any sprayed fields once earworm flight picks back up, as pyrethroids will remove a lot of beneficial insects.

Potato leafhopper are very active right now. A dynamic threshold developed by Penn State was incorporated into the alfalfa recommendation guide earlier this year and can be found here: