Viburnum leaf beetle

Disease Information

Viburnum leaf beetle

Pyrrhaltaviburni (Paykull)

Viburnum leaf beetle, Pyrrhaltaviburni (Paykull), is a chrysomelid beetle, aptly named, as it feeds on leaves of viburnum. The damage potential from the beetle is quite extensive, if not managed.

DESCRIPTION OF THE PEST

Viburnum leaf beetle overwinters in the egg stage. Eggs are inserted into pits chewed into the stems, generally in a straight line. Larvae hatch from the eggs in the spring mid-late April. There are three larval stages (instars). Larvae eventually drop or crawl down the trunk of the plant to pupate in the soil. Pupae remain in the soil for about 10 days. Adults are found in the summer in July. Both larvae and adults feed on leaves. Adult females begin laying eggs in the late summer and fall. She can lay up to 500 eggs during her lifetime. There is only one generation per year.

 

Symptoms and damage

Look for oviposition scars on current year`s growth. Look for holes in leaves in the spring by the larvae. They usually feed on the leaf undersides. Like many leaf beetle larvae, they superficially resemble a caterpillar but lack crochets (hooked appendages) on the prolegs. The newly hatched larvae are very small, around 1/8" long and are light yellow to tan. Their feeding damage tends to be leaf skeletonization. Larger larvae are light to dark green with black spots.The adult beetles are bronze-brown color and similar in size to an elm leaf beetle. Feeding by the adults tend to show up as larger holes in the leaves. Dieback from oviposition can also lead to terminal dieback on stems.

Management

The most effective means of control for small scale plantings is pruning and destroying infested twigs after egg laying has ceased in the fall, anytime from October to April. When pruning is not practical, a number of pesticides may be effective in controlling VLB.

Home gardeners may use acephate, carbaryl, cyfluthrin, imidacloprid, or malathion. Spray when larvae first appear in early May for best results. If damage from adults is excessive, a second application in mid- to late-summer may be helpful.



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