It was hard to get sleepy driving through Illinois this week. Japanese beetles thudded against the windshield with sickening regularity. I might have felt better about the situation if they had splatted rather than plinked—at least it would have given me the illusion I was helping to control the population.
“Growers need to be scouting because peak densities of Japanese beetle and corn rootworm adults may coincide with the period of silking and pollination this year,” says Kevin Steffey, University of Illinois extension entomologist.
Late planting and slow development the corn crop puts it at risk. Steffey says insecticide applications may be warranted when there are three or more beetles per ear and pollination is not complete.
“Place an emphasis on the amount of silk clipping,” he says. “Over the years experienced agronomists have observed that some corn hybrids escape the ravages of silk-clipping insects, either by rapid silk growth or the fact they don’t like the taste of that hybrid.”
Soybeans require careful scouting too. Traditional defoliation levels suggest economic thresholds are 30% before bloom and 20% between bloom and pod fill. Because the soybean crop is so valuable this year, growers may want consider lower thresholds.
For More Information
Japanese beetles
Managing Adult Japanese Beetles, University of Kentucky
Ohio State University Extension Fact Sheet: Japanese Beetle
Approved Insecticides
Illinois Agricultural Pest Management Handbook
You can email Pamela Henderson Smith at psmith@farmjournal.com.
