An adult viburnum leaf beetle (Pyrrhalta viburni), a dangerous pest for viburnum shrubs.
Photographer: Ettore BalocchiThe viburnum leaf beetle (Pyrrhalta viburni) is a serious pest of viburnum plants in Canada and the northeastern U.S.

This Eurasian beetle arrived in the United States in the early 1990s. By 2008, it had been documented in New England, New York, New Jersey, Pennsylvania, Ohio, Michigan as well as Ontario and the Canadian Maritime Provinces.

The adult is a tiny brown adult beetle the size of a matchstick head. It lays eggs in imperfect rows of chewed holes underneath younger twigs in summer and until the first frost.

A late stage viburnum leaf beetle larva on a skeletonized viburnum leaf.
Photographer: Flickr user dogtooth77In spring, tiny pale larvae emerge to feast on viburnum leaves, eating their way through three stages of change, and leaving behind skeletons of leaf veins. Then they crawl down the plant to build a cocoon in moist soil.

Later in the summer, the adults emerge, find undamaged leaves, and eat little oblong bullet-holes through them. Repeated infestation can kill the plants.

The most effective control of this pest is to prune and destroy egg-infested twigs from late fall to early spring. Beneficial insects like ladybug larvae and adults and even certain stinkbugs feed on the viburnum leaf beetle or its larvae.