Regulated chemicals, such as carbaryl, pyrethroid and permethrin, offer immediate knockdown of Japanese beetles. Commercial pesticides that contain pyrethroid include Bayer Advanced Lawn and Garden Multi-Insect Killer and Tempo. Both pyrethroid and carbaryl not only kill adult beetles, but also provide about two weeks of protection to plants.
Spraying dissolved insecticidal soaps directly at Japanese beetles is also an effective method to eliminate adult beetles. Unlike stronger insecticides, however, it does not have residual effects, allowing other beetles that have not been hit directly by the sprayer to survive.
While eliminating the adult Japanese beetles may reduce damage to plants and crops, getting rid of grubs under the ground prevents further infestation. Timing of pesticide treatment is important because insecticides do not work for grubs in pupal stage. The best time to apply insecticides for grubs is from mid-July to early September when adult Japanese beetles fly to the grass to lay their eggs. Some effective grub insecticides are imidacloprid, trichlorfon and halofenozide.
A Japanese beetle is a highly destructive pest. Both the larvae and adult forms of the Japanese beetle incur damage to fruit trees, shrubs, ornamental vines and vegetable and field crops. Adult Japanese beetles feed on and leave skeletonized leaves, while the grubs remain underground and feed on the roots of the plants. They are more prevalent in golf courses and lawns, causing widespread turf damages.