Elm Leaf Beetle Information

Adult Elm Leaf Beetles are yellow to olive green and ¼ inches long. They have a dark stripe down each side of their wing covers and a dark thin strip down the center of their back. Often confused with the western corn root worm and the striped cucumber beetle, the elm leaf beetle is positively identified by the four dark spots behind its head, black eyes and yellow antennae.
(See picture of Adult Elm Leaf Beetle.)
The eggs of the elm leaf beetle are orange and are laid in double rows of five to twenty five on the underside of the leaf. Larvae are black and ½ inches long while the pupas are orange to yellow with black bristles.
(See picture of egg and larvae of Elm Leaf Beetle.)
At the beginning of winter, elm leaf beetles are attracted to the warmth coming off of nearby buildings. They make their way into cracks in the exterior walls of buildings, through vents and loose fitting screen doors. As months begin to get warmer, they have been known to move inside the building making themselves a nuisance when they congregate in large numbers. When inside buildings, they are often confused with carpet beetles.
The adult Elm Leaf Beetle survives the winters in woodpiles, under debris and in the cracks of homes. During this time, they do not feed or reproduce but rather become active when the weather turns warm. In early spring, these beetles fly to elm trees full of foliage and feed on the leaves producing small holes.
After feeding, adult elm leaf beetles lay a double row of eggs on top of the leaf. After a week, black worm like larvae emerge and feed on the underside of the leaf and “skeletonize” it leaving the upper parts and larger veins. The skeletonized damage can be seen in the picture of Elm Leaf Beetle Larvae damage.
This skeletonized damage gives the foliage a net like appearance. Areas around where the larvae feed dry up and die, and sometimes make the leaf fall off the tree.
As the larvae grow, they repeatedly shed their skins and are full grown after a few weeks. They then stop feeding and pupate in a curled position, either at the base of the tree or within the folds of the bark. (See picture of Elm Leaf Beetle Pupae)
After two weeks of pupating, they emerge as an adult. This cycle begins all over again in mid summer. The adult female elm leaf beetle may produce 600 to 800 eggs during her lifetime. Due to this vast number, larvae are much more destructive to the elm leaves than adults.
Enemies of the elm leaf beetle are stink bugs and plant bugs, fungus disease, and the weather. Long winters or late spring freeze kill the beetle as well as storms during which they can be blown off the trees. Two types of wasps were introduced into the United States to help maintain control by killing the elm leaf beetle eggs, but over the years have failed to survive.
Due to the elm leaf beetle, leaves that are infested die and give elm trees a general brown color. Repeated infestations weaken the trees and make them prone to branch dieback and wind injury. Elm leaf beetles favor Siberian elms and American elms, but will feed on all types of elms. Contrary to popular belief, the elm leaf beetle does not transmit Dutch elm disease. This disease of the American elm is spread by the elm bark beetle.

Information and research on Elm Leaf Beetle article provided by Lani Powell.