Insect of the Week: the Japanese Beetle

Adapted from pages 202-203 of Garden Insects of North America:

Adult Japanese beetles feed on foliage of more than 300 species, including rose, mountain-ash, willow, linden, elm, grape, Virginia creeper, bean, Japanese and Norway maples, birch, pin oak, horse chestnut, rose of Sharon, sycamore, ornamental apple, plum, and cherry. Larvae develop on roots of various grasses. The Japanese beetle is one of the few beetles that is highly damaging in both the adult and larval stages. Adults feed on foliage and flower petals, producing skeletonizing injuries that cause leaves to appear lacelike. In high populations they may completely consume flower petals and more tender foliage. The larva, a type of white grub that feeds on grass roots, is among the most damaging pests of turfgrass in the northeastern quadrant of the U.S. Originally introduced into New Jersey and now important in the northeastern U.S. and parts of southern Canada. This species ranges into Colorado to the west, Arkansas to the south, and is found in parts of northern Alabama, northern Georgia, and South Carolina. Its range continues to expand, with localized infestations present in many other states.

The life stages of a Japanese beetle (Popillia japonica). Photo credit: David Shetlar

Adults are generally metallic green with bronze wing covers. A row of white hair brushes is present along each side. The overall form is broadly oval, and length ranges from about 1/3 to nearly 1/2 inch. Larvae are typical white grubs, C-shaped when at rest and a translucent creamy white, and feed on organic matter in the soil or under turf. Winter is spent in soil as a nearly full-grown grub that moves deeper into the soil for winter. As soils warm, the grubs resume feeding on grass roots and pupate 2–4 inches below the surface, in a tamped earthen cell. Adults emerge in late June and early summer, feed on foliage, and mate, returning to lawn near sunset. The aggregation pheromones these insects produce combined with attractive odors produced by their food plants often result in large numbers feeding together. Females lay eggs in small masses in soil cavities they excavate 2–4 inches deep. Most eggs are usually laid by early August, but some are laid into September. Over most of its range Japanese beetle has a 1-year life cycle, although it may extend to 2 years in the extreme northern areas where it occurs.

Garden Insects of North America: The Ultimate Guide to Backyard Bugs
Second Edition
By Whitney Cranshaw & David Shetlar

This second edition of Garden Insects of North America solidifies its place as the most comprehensive guide to the common insects, mites, and other “bugs” found in the backyards and gardens of the United States and Canada. Featuring 3,300 full-color photos and concise, detailed text, this fully revised book covers the hundreds of species of insects and mites associated with fruits and vegetables, shade trees and shrubs, flowers and ornamental plants, and turfgrass—from aphids and bumble bees to leafhoppers and mealybugs to woollybears and yellowjacket wasps—and much more. This new edition also provides a greatly expanded treatment of common pollinators and flower visitors, the natural enemies of garden pests, and the earthworms, insects, and other arthropods that help with decomposing plant matter in the garden.

Designed to help you easily identify what you find in the garden, the book is organized by where insects are most likely to be seen—on leaves, shoots, flowers, roots, or soil. Photos are included throughout the book, next to detailed descriptions of the insects and their associated plants.

An indispensable guide to the natural microcosm in our backyards, Garden Insects of North America continues to be the definitive resource for amateur gardeners, insect lovers, and professional entomologists.

  • Revised and expanded edition covers most of the insects, mites, and other “bugs” one may find in yards or gardens in the United States and Canada—all in one handy volume
  • Features more than 3,300 full-color photos, more than twice the illustrations of the first edition
  • Concise, informative text organized to help you easily identify insects and the plant injuries that they may cause