Elm leaf beetles can defoliate elm trees; repeated defoliation over several years severely stresses trees. The beetles and their larvae skeletonize elm leaves, leaving lacy brown holes in leaves and causing leaf drop. Elm leaf beetle populations fluctuate from year to year and therefore do not need to be managed every year.
American elms, English elms, Scotch elms, and some hybrid elms
Healthy elm trees can tolerate substantial defoliation by elm leaf beetles, so chemical treatment methods should be used sparingly. Insecticide sprays can control outbreaks of the beetle but should be conducted under the supervision of a certified arborist. Since elm leaf beetles can fly, spraying treatments are most effective when the entire neighborhood is treated.