Japanese Beetles are in Full Force – Turfgrass Science at Purdue University

Japanese Beetles are in Full Force

The first Japanese beetles of the year were observed in central Indiana on June 22 and have since come out in full force. They are being reported in large numbers from many places throughout the state feeding on their favorite plants. Plants particularly at risk include those that have been recently transplanted or those that are stressed for one reason or another. Favorites for Japanese beetle include linden, crab apple, plum, and other fruit trees, rose bushes, grapes, and several garden variety vegetables. Physical (netting or picking off the beetles each day) or chemical controls (Sevin, Orthene, Malathion or any of several pyrethroids) may be required to protect plants from Japanese beetle defoliation. After adult beetles mate they will lay eggs in turfgrass areas. The resulting larvae, called white grubs, can also be very devastating as they prune the roots off of the grass. If the current drought continues, egg laying may be concentrated in irrigated turf areas. Insecticides available for grub control only work AFTER the grubs have hatched – usually the end of July or the first part of August. Two very effective grub control products include imidacloprid (Merit) and halofenozide (Mach 2). A more recent addition to the professional market is Clothianidin (Arena) and we expect it to be as efficacious as imidacloprid and halofenozide, but more testing and experience will be needed to confirm this. These products are long-lasting but must be applied as preventative treatments. They are most effective if applied from late June through July. As with all insecticides, it is critical to follow the label directions exactly when making applications. For grub control products it is recommended that 1/2 inch of irrigation be applied immediately after treatment. In cases where irrigation is not possible, timing the application to just before a significant rainfall event is recommended.

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