Forest Pests: Insects, Diseases & Other Damage Agents

Japanese Beetle
Popillia japonica Newman

Hanson, T., and E. B. Walker. [n.d.] Field guide to common insect pests of urban trees in the Northeast. Waterbury, VT: Department of Forests, Parks and Recreation.

Coleoptera: Scarabaeidae Hosts: Apple, cherry, maple (especially Norway), littleleaf linden, birch, elm and many other hardwood species of trees; foliage and flowers of many shrubs are also attacked Evidence: From early July through September, the adults, with metallic green bodies (a), can be found on leaves, sometimes several per leaf (b). Young tender leaves are preferred and may be completely skeletonized by adults (c). The C-shaped larvae (grubs) can seriously damage grass roots and can be found under dead patches of lawn. Life Cycle: There is one generation per year. Most of the year is spent as larvae in the soil. Larvae overwinter in earthen cells 4-12 inches below the surface. From early spring until June, they continue to feed on roots. Then the insects pupate near the soil surface. Adults fly in the daytime and are active on sunny, warm days over 6-12 weeks, beginning the first week of July. Eggs are laid in the soil, and larvae feed on roots into the fall.	a. Adult Japanese beetles feed on leaves and fruit of more than 200 plants.
	b. Japanese Beetles may be found on foliage from July through September.
	c. Feeding gregariously, Japanese Beetles may skeletonize leaves completely.

Management: Feeding on underground stems and roots of grasses may go unnoticed until plants fail to grow or die. Eggs and newly-hatched larvae are killed by extremely dry weather, while wet summers are usually followed by seasons of increased numbers of beetles. Predators of grubs include birds, moles, skunks, and occasionally raccoons. Beetles can be hand-picked and destroyed if there are not too many. Chemical insecticides, in the form of granules or sprays, can be effective in controlling larvae in soil and turf. If there are more than 8 to 15 larvae per square foot in tall fescue, or 6 to 8 per square foot in blue grass, treatment is suggested. Chemical treatments can also be made to foliage of susceptible trees and shrubs.

Photo Credits: Figure a: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.

Figure c: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.

References:

Johnson, W.T. and Lyon, H.H. 1991. Insects That Feed on Trees and Shrubs. 2nd edition. Cornell University Press. p 236-237.

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