Pest description and damage The adult poplar-and-willow borer is a black and pink to cream-colored weevil (a flightless snout beetle) about 0.375 inch long. The larvae are white, legless, and about 0.25 inch long at maturity. Larvae feed by mining beneath the bark of trunk and branches. In late summer, feeding larvae expel large quantities of sawdust-like frass (excrement) through holes in the bark accompanied by flow of a thin sap. Larval feeding may girdle branches, resulting in breakage, leaf wilt or eventual branch death. Severe infestations cause lumpy, swollen bark, with cracks and bark scars with exposed wood. Old wood may produce large numbers of new shoots. Willows are the preferred host, but the poplar-and-willow borer also attacks poplars. The adults chew small holes in the bark of twigs and shoots, introducing a fungus which may cause shoots to wilt. This insect has become a serious problem in hybrid poplar plantations, and in willows grown for the cut flower industry and restoration plantings. In landscapes, damage is most common on native willows.
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