Japanese beetles-a destroyer of plants
By JOAN CROTHERS Sentinel Editor

Stages of development of a Japanese beetle (l-r) egg, larva, pupa, and adult.

Metallic green bodies with bronze outer wings make 1/2" long Japanese beetles hard to miss. But if you don't notice the insect you'll notice the damage as they skeletonize leaves. This beetle eats not just the leaves, but the flowers and fruit of some 300 kinds of trees and shrubs, especially loving roses.

The Japanese beetle is an alien, so has few natural enemies -except the starling, which is itself an alien. Like many other insects, Japanese beetles pass through various stages of development Adult beetles are most common in spring and early summer as they feed. During this time, the females burrow into the ground where they lay eggs.

After the eggs hatch, the larvae do a different kind of damage. The 1" long white grubs often live under turfgrass, feeding on the roots. A heavy infestation can kill sections of lawn, which you can pull back like carpet to see the grubs underneath (if you d this, kill any you see). Moles, raccoons and birds like to feed on the grubs, but apparently don't find enough of them. The larvae overwinters several inches underground. They pupate in the spring and emerge as adults in spring or early summer.

An iridescent Japanese beetle, seen here making lacework of an alder leaf.

Control: You can buy traps at most hardware or garden centers, but they're not the best way to deal with this pest. They often attract more beetles than they actually catch, making the problem worse. In fact, many sources on this subject are emphatic about NOT buying traps.

Insecticides, including imidacloprid and carbaryl, can control the larvae in lawns. But there are more environmentally friendly ways to dispose of the grubs with insecteating nematodes (Steinenema glaseri and Heterorhabditis bacteriophora) that control Japanese beetles in turfgrass. Milky spore, applied anytime the ground isn't frozen, controls the larvae too. It comes in a powder that you mix up and water into the soil.

If you only have a few beetles, or feel so inclined, go out with a pail of soapy water and pick them off your plants and drown them. They are less active in the early morning or late evening which is also a cooler time for you.