The presence of many eggs indicates a high probability of severe defoliation. Both larvae and adults skeletonize elm leaves, leaving nothing but the leaf veins if the attack is severe. Most trees will not be killed unless the defoliation is nearly complete for two or three consecutive years. Two generations of spotted black and yellow larvae are produced each year in Nebraska. The first usually occurs from May to June and the second from July through August.
Adults emerge one to two weeks later.
In the home Preventing invasion of elm leaf beetles into the home in the fall will forestall nuisance problems in the winter. Migration from host trees to sheltered areas is gradual and may not be noticed. Seal all cracks and crevices that could allow entry, and make certain that window and vent screens are intact. If elm leaf beetles enter the home, remove them with a vacuum cleaner. Follow label instructions.