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Japanese Weevil



Authors as Published

Eric R. Day, Director, Insect Identification Laboratory, Virginia Tech

Coleoptera: Curculionidae, Pseudocneorhinus bifasciatus

Plants Attacked

The Japanese weevil has a long list of hosts, but is especially found on cherry laurel, broad-leaved evergreens, pyracantha, privet, barberry, euonymus, and many others.

Description of Damage

Foliage is more or less chewed, beginning as marginal notches and increasing to large rounded sections of the leaves being consumed. Holes are always cut inward from the margin, never in the inner part of the leaf. Larvae feed on roots of plants in the soil, but their habits are not well known, nor is the extent of the injury they produce. Injury is not distinguishable from that caused by black vine weevil, fullers rose beetle, and other species.


The adults are a mottled, grayish, light brown. The bodies are more round and stubby than elongate as with many weevils. Although they feed in daytime, Japanese weevils frequently hide under leaves or in crotches and are not easily detected in light infestations. Larvae are legless, more or less C-shaped grubs in the soil, seldom seen or found. Japanese weevils, Pseudocneorhinus bifasciatu, are in the order Coleoptera and the family Curculionidae.




Life History

Little is known about the life history of this weevil. Adults are most frequently found first during mid to late June and continue to inhabit host plants and feed over several weeks or more. Presumably, they lay their eggs in the soil during midsummer and the larvae feed on plant roots until late the following spring. Adults cannot fly since the wing covers are fused together. There is one generation per year. Overwintering isdone by larvae in the ground.


It is best to spray tree trunks, branches, and foliage during the second or third week of June, but trees can be treated whenever the weevils are seen. Products containing imidacloprid should provide effective control if applied as a soil drench just as growth starts in the spring.


There are reports in the literature that populations have built up into the thousands on occasion. There are no recent records of such outbreaks, although light infestations are relatively common in the southeastern part of the state. The Japanese weevil is known to be equally abundant northward to and including Long Island, New York.


Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.


Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Alan L. Grant, Dean, College of Agriculture and Life Sciences; Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.


May 1, 2009

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