Twobanded Japanese Weevil

Introduction

Twobanded Japanese weevil (Figs. 1 & 2; Pseudocneorhinus bifasciatus) attacks a wide range of trees and shrubs in the landscape, including cherry laurel, broad-leaved evergreens, pyracantha, privet, barberry, euonymus, and others. This weevil is an occasional pest of soybeans and vegetables in Virginia.

Identification

Adult twobanded Japanese weevils are small, measuring about 0.25” long (6 mm). They are a mottled, grayish, light brown, often with a broad gray band outlined in dark brown across the width of the wing covers (Fig. 1). Their bodies are stout and pear-shaped, with bristly hairs on the head, legs, and wing covers (Fig. 2). The snout is relatively blunt and short for a weevil. Twobanded Japanese weevils feed during the day, but they frequently hide under leaves or in crotches of limbs, so light infestations are not easily detected. When disturbed, they quickly drop to the ground and act as if they were dead. The wing covers of adult twobanded Japanese weevils are fused together so they cannot fly. Movement of infested nursery stock is thought to transport this pest into new areas.

Larvae of the twobanded Japanese weevil are small, legless, C-shaped grubs. Their bodies are whitish with a brown head capsule. They are seldom noticed living underground.

Life History

The life history of the twobanded Japanese weevil has not been thoroughly studied. Populations in the United States appear to be parthenogenetic, as males are rarely found. Females hide their eggs in leaf folds made by folding over the edges of leaves on the host plant. Larvae hatch and drop to the soil to feed on the roots of adult-infested plants.

Twobanded Japanese weevil overwinters in the soil, and adults emerge in mid to late June. Adults feed and lay eggs until cooler weather in the fall; some adults may overwinter in leaf debris. There is one generation per year.

Damage

Adult twobanded Japanese weevils defoliate leaves by notching leaf margins (Fig. 3). Damage begins as marginal notches and increases to large, rounded sections of the leaves being consumed. Holes are always cut inward from the margin and never in the inner part of the leaf. These characteristic notches can be used as an early indicator of larval populations in nearby soil. Marginal leaf notching on broad-leaved evergreens resembles damage caused by similar root weevils such as the black vine weevil (https://www.pubs.ext.vt.edu/444/444- 210/444-210.html), Fuller rose beetle, and other similar species of root weevils. Twobanded Japanese weevil larvae feed on plant roots in the soil, but their habits and the extent of their feeding damage are not well known.

Management

Scouting: Monitor host plants for the distinctive leaf notches made by feeding adults. Adults are diurnal feeders. They can be collected by placing a white sheet under the host plant and gently tapping the foliage to dislodge any adults present. Drown adults in soapy water, put them in a freezer for several days, or destroy them in another manner.

Chemical Control: Spray the trunks, branches, and foliage of plants infested with twobanded Japanese weevils during the second or third week of June, when adults have emerged from the soil but have not laid many eggs yet. Host trees and shrubs can be treated as soon as the weevils are observed. See the Virginia Pest Management Guide for Home Grounds and Animals (https://www.pubs.ext.vt.edu/456/456- 018/456-018.html) or Horticulture and Forest Crops (https://www.pubs.ext.vt.edu/456/456-017/456- 017.htmls.html) for specific insecticide recommendations depending on homeowner or commercial production use. Products containing imidacloprid should provide effective control if applied as a soil drench just as fresh plant growth starts in the spring.

Cultural Control: Purchase pest-free nursery stock whenever possible. Leaves should not have any notched leaves, which may indicate twobanded Japanese weevil larvae are present in the container’s soil.

Note

There are reports in the literature that populations of twobanded Japanese weevil occasionally built up into the thousands. There are no recent records of such outbreaks, although light infestations are relatively common in the southeastern part of Virginia.

A closely related species, Pseudocneorhinus obesus, has recently been recognized in the eastern United States and is thought to have a life history similar to the twobanded Japanese weevil.

Revision

Theresa A. Dellinger, 2020, and August 11, 2025.