Imported willow leaf beetle (Plagiodera versicolor) adults are metallic blue. This time of
year adults and larvae are feeding on willows. The adult beetles overwinter outdoors under bark or in leaf litter. They and emerge from hibernation sites in spring around the time willows start getting leaves since adults prefer new leaves. Females lay pale yellow eggs that hatch into voracious larvae. Adults and larvae skeletonize leaves which can give trees a brown cast as damaged leaves crisp in the sun. In some cases though they can eventually defoliate trees like the one I saw walking to work today. Insecticides labeled for leaf feeding beetles such as spinosad, imidacloprid, and chlorantraniliprole can be used if needed. Unfortunately, these beetles are here to stay so efforts to prevent any
damage to willows is in vain. High populations that cause complete defoliation pose a risk to tree health and may warrant management. Otherwise some damage is inevitable so go out and look at the beautiful beetles.