If your garden is attacked by Japanese beetles, the results can be devastating. Some consider these small but furiously destructive beetles the most invasive pest in the eastern United States. They’re also found in parts of southern Ontario and isolated areas of Quebec. These metallic green and copper insects, which are only about ½ inch long, wreak havoc from Wisconsin south to Alabama and east to the coast. Japanese beetles were accidentally introduced into the United States in 1916 in New Jersey. Previously, the beetles were only found in Japan, where they were not considered a major pest.

Damage
Japanese beetle larvae, or grubs, live in the soil for 10 months. The C-shaped grubs are white with a yellow-brown head, and they feed on vegetable seedlings and the roots of turfgrasses. In June, they begin to emerge from the ground. Adult beetles feed on about 300 species of grass, fruit, and flowers. Although they live for only 30 to 45 days, they can do considerable damage in that time. Japanese beetles are skeletonizers, which means they eat leaf tissue but leave the veins. Attacked leaves often look like pieces of lace, and they eventually wither and die.

Control
There are a few ways to handle Japanese beetles. If they’re a problem in your area, don’t choose plants that the beetles are known to love, like roses, grapes, Japanese maple, rose of Sharon, crabapple, and purple-leaf plum. If you already have Japanese beetles in your garden, try to shake them off plants in the early morning when the beetles are most sluggish and drop them in a bucket of soapy water. You can also apply milky spore bacteria—sprinkle it on the lawn to kill the beetles at the grub stage. Products that contain parasitic nematodes are also effective. (Nematodes are small worms that eat an insect from the inside out.) As a last resort, look for insecticides that kill Japanese beetles in both the grub and adult stages. Check with your local extension service to see which insecticides are recommended in your area.


—text by Elyse Lucas, photo courtesy of the Kemper Center for Home Gardening at the Missouri Botanical Garden