Elm Leaf Beetle
About Elm Leaf Beetle
Lives on American and Siberian (Chinese) elms.
Small larvae are black and hairy; large larvae are yellow with two longitudinal dark stripes. Adults are 5 to 7 mm long, yellowish-green, and have a black stripe on the outer margin of each wing cover. Three black spots are present behind the head.
Elm leaf beetles overwinter as adults in sheltered dry areas, especially in and around buildings and in litter and bark crevices. They emerge when buds begin to expand in the spring and feed on leaves before laying clusters of yellow eggs on foliage in late spring.
Larvae skeletonize leaves for 2 to 3 weeks before pupating. There are two or three generations per year. Shade trees are often heavily defoliated, making them weak and unsightly.
To Control
Spray elm leaves with carbaryl or methoxychlor to kill larvae and adults. Do not spray when the weather is hot and dry. Inject systemics recommended by your extension service (see our Links section) into the trunk or apply them to the soil. Spray pupae larvae clustered at the base of the tree with carbaryl or methoxychlor, or pour boiling water or a light oil on them.