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By Wayne Flanary, Extension Agronomist
Japanese beetles emerge from the soil from June to August. We have received several calls from producers asking questions regarding this pest.
Japanese beetles continue to expand on the area where they have been found. This is quite alarming to growers as they find a pest they are not familiar with in their fields.
The Japanese beetle lives as a grub in the soil and feeds on roots of plants. As they emerge as beetles, they are metallic-green with bronze-colored wing covers. Just beneath the wing covers, along each side of the abdomen, are six tufts of white hair.
To scout for beetles in corn and soybeans, check plants during the adult stage of the insect. Beetles tend to aggregate in large numbers so feeding damage appears worse than it is.
Soybean economic thresholds are based on the percentage of defoliation, not the actual numbers of beetles. Feeding often begins at the top of the crop canopy. Thresholds for insecticide application are 30% defoliation before flowering and 20% between flowering and mid pod fill.
Corn economic thresholds are — three or more beetles present on green silk, silks eaten to one-half inch or less in length, and pollination less than 50%.
Japanese beetles feed on a wide variety of vegetables, tree fruits and ornamental plants and trees. If you do not have them now, you will probably have them in the future.
For more information, contact Wayne Flanary at 660-446-3724 located in Oregon or Andy Luke at 816-425-6434 located in Bethany, Extension Agronomists, University of Missouri Extension.