NC State Extension Publications

General Information

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Twobanded Japanese weevils, Pseudocneorhinus bifasciatus, are about 1/4 inch long and are light or dark brown to gray with a short, blunt snout. The wing covers (elytra) have indistinct white stripes in grooves, white spots toward the back, and two darkbrown or black transverse bands. Eggs are small, elongate, and cream colored. Fully-grown larvae are white, legless, and just over 1/4 inch long. The pupa is white with yellow-brown setae, and is about 1/4 inch long.

Twobanded Japanese weevil

Twobanded Japanese weevils are about the size of a pencil eraser.

Twobanded Japanese weevils feed

Twobanded Japanese weevils feed on the edges of leaves, making plants look tattered.

Twobanded Japanese weevils hide their eggs

Twobanded Japanese weevils hide their eggs inside a folded leaf.

Twobanded Japanese weevil grub

Twobanded Japanese weevil grubs have a brown head and lack legs.

Biology

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We assume Japanese weevils are parthenogenetic because no males have been recorded in the United States (Males have been collected in China). Eggs are deposited in small batches protected by folds along leaf margins that form a pod around the eggs. Females can lay over 350 eggs each when feeding on rose. As the eggs hatch, the larvae burrow into the ground and feed on the roots. These weevils lack flight wings, have fused wing covers, and are unable to fly. They feed during the day, but if disturbed, twobanded Japanese weevils drop to the ground and remain motionless. In autumn, the weevils hibernate in leaf litter and resume feeding the following spring. One generation occurs each year although there is some overlap of overwintering and new adults during the growing season.

The twobanded Japanese weevil was first found in the United States in 1914 near Philadelphia. It is now established in the eastern United States. Some of the plants attacked by the twobanded Japanese weevil are ash, azalea, barberry, burr marigold, camellia, dogwood, lilac, mountain laurel, privet, rhododendron, rose, spirea, strawberry, and weigela. Twobanded Japanese weevil larvae feed on plant roots, but the adults do serious and apparent damage. The weevils feed extensively on new leaves, shoots, and inner foliage. As a result, infested plants are tattered and unhealthy in appearance.

Control

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Because twobanded Japanese weevils feed during the day but drop from infested shrubs when disturbed, many can be trapped and destroyed. Taking care not to jar the plant, place a white cloth or large sheet of paper under the shrub and then tap or shake the plant vigorously. Many weevils will fall off and can be easily collected. Destroy the weevils by dropping them into a can of water with a small amount of solvent or by freezing them or some other method.

Twobanded Japanese weevils are apparently resistant to carbaryl (Sevin), diazinon, and malathion. Commercial growers and landscapers can use a pyrethroid (Astro, Mavrik, Talstar or Tempo 2) for control. Homeowners may find BioNeem and formulations of bifenthrin,cyfluthrin or permethrin at lawn and garden centers.

Tests on the similar black vine weevil show pesticides may be applied to the media or soil surface as a drench to control black vine weevil larvae. Imidacloprid (Merit, Marathon) can be used as a soil injection or drench against larvae. Scimitar & Demand (Oregon study) and Talstar (Ohio study) are effective when adults are present. Aloft may also be an effective product.

Pesticide (Trade Name) Formulation Amount
acephate (Orthene) 75% soluble powder 1 tablespoon per gallon for tree and ornamental. 1 pound per 100 gallons of water. (Not labeled for twobanded Japanese weevil but labeled for black vine weevil, strawberry root weevil, root weevil, and numerous other pests on many ornamental plants.)
acephate (Orthene) 9.4% emulsifiable concentrate 3 tablespoons per gallon of water. (Not labeled for the twobanded Japanese weevil but labeled for black vine weevil, obscure root weevil, and numerous other pests on many ornamental plants.)
azadirachtin (Azatin EC, BioNeem) 3% emulsifiable concentrate Azatin EC is federally labeled for twobanded Japanese weevil but the pests and rates of application are not listed.

Other Resources

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For assistance with a specific problem, contact your local Cooperative Extension center.

Authors

Professor and Extension Specialist
Entomology & Plant Pathology
Professor Emeritus
Entomology & Plant Pathology

Publication date: Aug. 1, 1994
Revised: Oct. 17, 2019

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