This article is part of our Organic Pest Control Series, which includes articles on attracting beneficial insects, controlling specific garden pests, and using organic pesticides.
Japanese Beetles (Popillia japonica)
Since first being found in New Jersey in 191
This article is part of our Organic Pest Control Series, which includes articles on attracting beneficial insects, controlling specific garden pests, and using organic pesticides.
Japanese Beetles (Popillia japonica)
Since first being found in New Jersey in 1916, Japanese beetles have become major garden pests in eastern North America. Appearing in early summer, the coppery beetles feed on leaves of roses, grapes, beans, hops, and more than 300 other plants, including lindens and several other landscape trees. Larvae feed in lawns and weaken the grass by destroying roots.
Organic Japanese beetle controls include repeated handpicking, poultry predation, row cover barriers, and beneficial nematodes or diatomaceous earth applied to lawn areas. Japanese beetle traps require special handling, because they can attract more beetles than would otherwise be present.
What Are Japanese Beetles?
This summer pest feeds for only about six weeks, but its voracious appetite, copper coloring and sexual behavior immediately get gardeners’ attention. Half-inch long beetles with copper backs, green heads, and white dots along their rears are Japanese beetles. They are often first seen on roses, but also love raspberries, grapes, beans, hollyhocks, and a long list of other popular garden plants. In bad years Japanese beetles appear in swarms, typically during the second half of June and especially in areas where they are a recently established pest.
What Japanese Beetle Damage Looks Like
Japanese beetles emerge in early summer and begin feeding on plants they prefer. They rasp away tissues on the top sides of leaves, which often leads to jagged holes. Japanese beetle larvae, or grubs, cause lawns to feel spongy underfoot. Lawns that are badly infested with Japanese beetles show thin growth and dry out quickly. In trees, Japanese beetles often start at the top and work their way down, causing the crown of infested trees to look mottled tan.
Japanese Beetle Life Cycle
Japanese beetles overwinter as almost-mature larvae deep in the soil, often more than 10 inches deep. As the soil warms, the larvae move upward and pupate, and emerge as hungry beetles. They feed constantly for about six weeks. Each afternoon, females visit grassy areas to lay eggs. These eggs hatch into small white grubs that 