Origin:
This is a native beetle in North America, and is found from Alaska south to California and east into much of the rest of the U.S. and Canada.
Biology:
This is one of several species of leaf beetles in this genus. Willow is the favored host plant, but they also feed on cottonwood, alder, and other trees. The adult beetles overwinter on the bark or under materials on the ground and emerge in early spring. Eggs are laid and the larvae feed through the spring months, usually in clusters of many young larvae and on the undersides of the leaves, moving apart as they get older. Heavy feeding will cause the leaf to be skeletonized and to fall off the tree. Adult beetles also feed on the leaves. The larvae can emit a foul smelling fluid from glands along the sides of the body when they are disturbed, and this appears to repel most predators. There may be 4 generations each year, with the first generation causing the most damage to ornamental trees.
Identification:
This colorful beetle is about ΒΌ to 3/8 inch long and varies from dark metallic green on the elytra to a red ground color, with 7 large black spots on each elytron that often merge to form bands across the wings. The underside is black. Yellow bands are along each side of the thorax and the middle segment of each leg (the tibia) is also dark yellow. The larvae are elongate and tapering more narrow toward the back end. They are solid dark brown to black, but often with 2 pairs of yellowish spots on the first two segments of the thorax.
Characteristicts Important to Control:
Leaf beetles can be killed with applications of residual insecticides made when the larvae or adults are present on the foliage. Systemic insecticides applied to the soil are also very effective by moving the active ingredient up the tree and into the foliage to be eaten by the feeding beetle larvae. This application needs to be done well in advance of the presence of the larvae to give the active ingredient time to move up from the soil.
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