People living along the east coast of the United States have become all too familiar with voracious Japanese beetles chewing the leaves of trees, shrubs, and garden plants. This introduced pest was first found in Riverton, NJ in 1916 and has slowly spread across the eastern US moving just a few miles each year. This year we've spotted quite a few clusters of Japanese beetles feeding on pecan leaves in Cherokee Co. KS (home of the Pecan Experiment Field).
The Japanese beetle spends most of the year as a C-shaped grub-worm feeding in the soil on the roots of ground cover plants. Adults start emerging in mid-June and aggregate in large numbers on a single plant. The adults feed on over 300 species of plants including pecans. The beetles feed on leaf tissue but only remove tissue between leaf veins. This feeding behavior results in leaves with a skeletonized appearance (photo above).
Adult beetles have bright metallic coloration. The head and thorax are metallic green while the wing covers are copper colored (photo above). Upon emerging from the soil, adults release a strong pheromone that attracts other adults to the same location on the tree. Once aggregated, they feed on leaf tissue then shorty thereafter begin mating. Mated females will then drop to the ground to lay 30-40 eggs in the turf. Adult Japanese beetles are present for about a month's time, starting in mid-June and continuing until early July.
In our pecan orchard we have found Japanese beetles only on trees that did not receive the insecticide treatment we made in mid-June.