May beetles have the general shape of Japanese beetles but come in various shades of brown. They emerge from pastures and turfgrass, feed ravenously at night, and hide during the day. These beetles prefer, and may completely strip, the foliage from oaks, birch, elm, hickory, and walnut. Entire leaves may be eaten or petioles may be cut so leaves drop to the ground. May beetles also will feed on ash, fruit trees, hackberry, locust, Lombardy poplar, maple, plum, and willow. Damage often is heaviest on trees next to pastures or large expanses of turf – the source of these insects. May beetles have 2- to 3-year life cycles. Most of that time is spent as a white grub, feeding on the roots of grasses.
Insecticides labeled for trees and shrubs can provide some protection from feeding by these insects. Small trees, especially those that are relatively new in a landscape, can benefit from treatment but it is impractical to treat large, established trees, and they generally can tolerate moderate defoliation without harm.