Japanese Weevil
Contact: Eric Day, Manager, Insect Identification Laboratory
August 1996
Japanese Weevil
Coleoptera: Curculionidae, Pseudocneorhinus bifasciatus
Plants Attacked
Long list of hosts, but especially on cherry
laurel, broadleaved evergreens, pyracantha, privet, barberry,
euonymus, very many others.
Description of Damage
Foliage is more or less chewed beginning
as marginal notches increasing to large rounded sections of the
leaves being consumed. Never are holes cut in the inner part of
the leaf; always inward from the margin. Larvae feed on roots of
plants in the soil, but their habits are not well known, nor is
the extent of injury produced. Injury is not distinguishable from
that caused by black vine weevil, fullers rose beetle, and other
species.
Identification
The adults are mottled grayish light brown. The
body is more round and stubby than elongate as with many weevils.
Although they feed in daytime, they frequently hide under leaves,
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.
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. One generation per year. Overwintering
stage - larvae in the ground.
Control
Adequate tests for control of this insect have not been
tested. Trees should be sprayed during the second or third week
of June, preferably, but can be treated whenever the weevils are
seen. Spray trunk, branches, and the foliage.
Remarks
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.
Japanese weevil is known to be equally abundant northward to and
including Long Island, New York.
