Description: The elm leaf beetle, Pyrrhalta luteola, is an insect pest of elm (Ulmus spp.) trees in landscapes. Elm species susceptible to elm leaf beetle feeding include Siberian (Ulmus pumila), English (Ulmus minor), Scotch (Ulmus glabra), and American (Ulmus americana). The larvae and adults feed on leaves and may be present simultaneously. This publication provides information on the biology, damage, and management strategies that can be implemented to mitigate problems with elm leaf beetles.

Biology: The elm leaf beetle has four life stages: egg, larva, pupa, and adult. Elm leaf beetle adults are approximately 1/5 to ¼ inches (5 to 7 mm) in length, yellow to dull-green, with a black stripe on each side of the wing cover and one in the middle that extends the length of the body. In addition, there are two black spots on both sides of the thorax (middle portion), and two distinct short black lines just behind the thorax (Figures 1 and 2). Females lay clusters of five to 25 eggs on the underside of leaves along the veins. Eggs are yellow-orange and pointed at the tip. Each female can lay up to 800 eggs during her lifetime.

Larvae hatch (eclose) from eggs and are ⅓ to ½ inches (8.5 to 12.7 mm) long when mature. The larvae are dullyellow with two rows of tubercles extending down the side of the body that look like two black stripes. There are three larval instars (stages between each molt). Larvae are the most damaging life stage, feeding for approximately three weeks. Eventually, the larvae crawl down the trunk of a tree and pupate on the soil surfaceor underneath soil debris. Larvae may also remain on the tree and pupate in the cracks and crevices of the bark or large branches. Pupae are initially bright-yellow and turn yellow-brown during development.

Adults emerge (eclose) from the puparium after seven to 15 days and migrate upward on the tree trunk or fly to elm trees and feed on leaves. In late summer through fall adults depart trees and seek suitable sites to overwinter. Adults will overwinter in buildings, homes, and in protected places outdoors such as the bark of trees. Adults can be a nuisance pest inside homes when they enter in the fall or depart in the spring. There are two generations per year in Kansas.