Host: Elms, especially Chinese elm.
Importance: The elm leaf beetle (Pyrrhalta luteola) can strip an entire tree of leaves, causing growth loss, and limb or tree mortality.
Identification: Adult beetles are approximately ¼ inch long, and yellowish or greenish with black outer margins on the wingcovers. Legs and antennae are yellowish-green in color. Larvae are about ½ inch long and yellowish-green with two black stripes along the back. The head and legs are black. The pupae are about ¼ inch long and yellow-orange with a few black hairs. Eggs are small, spindle shaped, and yellowish-orange.
Signs of Attack: Skeletonized or shriveled brownish leaves are usually the first indication of an attack by this beetle. Examination of the leaves may reveal beetles, larvae or eggs.
Life Cycle: Adult beetles overwinter near the host tree, especially around buildings. In spring, they fly to the trees and begin feeding on new leaves. Mating and egg laying take place shortly and each female lays up to 25 yellow eggs in a mass on the underside of a leaf. A female beetle can lay several hundred eggs during her lifetime. Eggs hatch and larvae feed voraciously on leaves for two to four weeks. The larvae then crawl to some sheltered place on the tree or ground to pupate. In approximately two weeks, adults emerge to begin the cycle again. There are approximately three generations per year.
Control: No chemical controls are recommended for this insect under forest conditions. If populations build up on valuable ornamental or shade trees, the homeowner may wish to use insecticides to control the pest. Adult beetles and larvae are easily killed when sprayed with the recommended insecticide. (Use 80% SP sevin. Mix three Tbsp. sevin in one gallon of water. Cover foliage well with spray).
Photo Credits: Clemson University - USDA Cooperative Extension Slide Series; James Solomon, USDA Forest Service