Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001767
11/12/99
Japanese Beetle
The Japanese beetle is native to Japan and was introduced
into the United States before 1916. It now occurs
throughout much of the Eastern United States from Maine to
Georgia and west to the Missouri River. In Michigan, it
occurs in scattered locations in the Lower Peninsula south
of a line from Saginaw to Muskegon.
Descriptions:
The adult beetles are about 1/2 inch long and broadly oval
with a shiny metallic green forebody and copper-colored wing
covers. There are six small patches of white hairs on the
side of the abdomen. The larvae are typical C-shaped white
grubs. The grubs are 1 inch long when mature.
Life History:
The insect overwinters as a partially grown larva. In the
spring they move closer to the soil surface and feed on
grass roots. The grubs mature in late May or June and
pupate in the soil. The adults begin to emerge late June to
mid August. Peak adult activity, including mating and
egg-laying, occurs over the following 4-6 weeks. The
beetles begin to die off during the late summer. After
mating, the female beetles deposit 40-60 eggs in the soil.
The emerging grubs feed on grass roots until fall, when they
move downward in the soil. There is only one generation per
year.
Damage:
Both adults and larvae may cause economic damage. Adults
have been reported to feed on the foliage, flowers, or
fruit of over 275 plant species. The white grubs favor the
roots of grass plants and can cause serious damage to turf
grasses by eating the roots.
Control:
Lawns infested with Japanese Beetle larvae should be
irrigated at optimum levels. Frequently irrigated turf will
tolerate the grubs more readily than poorly maintained turf.
Traps can help to determine when Japanese Beetle populations
are high. However, the traps also attract additional beetles
into the area and should not be considered as control
measures.
Control measures for adult Japanese beetles should be
initiated as soon as beetles appear, but before serious
damage occurs. Where populations are high it may not be
possible to achieve satisfactory results.
Japanese beetle larvae can be controlled by applications of
pesticides. Applications should be made between August 15
and October 30 or March 12 to May 15.
Milky spore disease (Bacillus popilliae) is a biological
control of Japanese beetle grubs. However, it may require
a number of years to become firmly established in the soil
(at which time it becomes self-inoculating).
Summarized from MSU Extension Publication E-2655.
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This file was generated from data base ZZ on 01/19/00.
Data base ZZ was last revised on 11/12/99.
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