← All pests
Twobanded Japanese Weevil

Twobanded Japanese Weevil

Pseudocneorhinus bifasciatus

Insectalso: Japanese weevil, Two-banded Japanese weevil, Callirhopalus bifasciatus

A small, flightless brown weevil with a very broad appetite, chewing notches in the leaf margins of more than a hundred kinds of landscape plants. Every individual in the United States is female and lays viable eggs without mating, so populations build quietly.

🔎 How to spot it

Adults are about a quarter inch long, pear shaped, and mottled light to dark brown with a short, blunt snout and faint banding on the wing covers. Their wing covers are fused, so they cannot fly, and when disturbed they drop to the ground and play dead. The larvae are white, legless, and about a third of an inch long.

🥀 Damage it causes

Adults chew notches and scallops along the leaf margins, sometimes eating leaves back to the midvein, while the larvae feed on roots in the soil. The leaf damage is mostly cosmetic on established shrubs but can be heavy because so many beetles feed at once. Hosts include barberry, privet, lilac, rose, spirea, forsythia, viburnum, euonymus, azalea, and rhododendron.

🛡️ Prevent it

Because the adults cannot fly and play dead when disturbed, place a light cloth under a shrub, shake the branches, and collect and destroy the beetles that drop. Rake up and remove leaf litter and debris beneath host plants, where adults, eggs, and larvae overwinter. Monitor for the first marginal notching in spring.

🧯 If it is already here

Management is often unnecessary on healthy shrubs since the damage is cosmetic, but where control is wanted, treat when overwintered adults resume feeding in spring. Neem and azadirachtin products and entomopathogenic nematodes are options, and acephate has given good control where labeled. The beetles resist some older insecticides such as carbaryl, diazinon, and malathion.

💡 Good to know

There is one generation a year, and because the population is entirely female and parthenogenetic, a single beetle can start an infestation. It was introduced from Japan around 1914 near Philadelphia and is now a common landscape pest across the Northeast and Midwest. Its flightlessness makes hand-collection unusually practical.

🌱 Plants it attacks

45 plants in the library can be attacked by this pest

Alice du Pont MandevillaAmethyst Falls WisteriaAnnabelle Smooth HydrangeaApril Tryst CamelliaAugust Beauty GardeniaBachelor's ButtonBarbara Karst BougainvilleaBlue Bird Rose of SharonBurning BushClimbing HydrangeaClimbing Prairie RoseCoral Drift Groundcover RoseDiabolo NinebarkEarly Amethyst BeautyberryEndless Summer HydrangeaFlowering DogwoodGoldflame SpireaGraham Thomas English RoseHansa Rugosa RoseHummingbird SummersweetIceberg Floribunda RoseJackmanii ClematisJapanese BarberryKaren AzaleaKnock Out RoseLimelight Panicle HydrangeaLynwood Gold ForsythiaMajor Wheeler Trumpet HoneysuckleMiss Kim LilacMiss Molly Butterfly BushMister Lincoln Hybrid Tea RoseMoss RoseNew Dawn Climbing RosePeace Hybrid Tea RosePJM RhododendronPrivetPurple Smoke False IndigoQueen Elizabeth Grandiflora RoseQuinceRoyal Heritage Lenten RoseShasta Doublefile ViburnumSnow Queen Oakleaf HydrangeaSweet Chariot Miniature RoseTexas Scarlet Flowering QuinceWine and Roses Weigela

For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.