Issue 7, June 16, 2014

May Beetle

True white grubs, also known as 3-year white grubs and May beetles, consist of many species in the genus Phyllophaga in Illinois. Their life cycle varies from 1 to 3 years. At least one 3-year species is present as adults at this time. These 1-inch-long, reddish-brown to dark brown, stocky May beetles are active at night, feeding on the foliage of oak, ash, crabapple, and other deciduous trees. They eat the edges of the leaves, occasionally removing leaf tissue to the mid-vein. Because the feeding occurs at night, no pest is seen during the day: They are hiding in the thatch of the lawn. Scouting the trees after 9 p.m. usually reveals the feeding beetles. Several insecticides are effective in controlling these leaf-feeding beetles, but the damage is usually not heavy enough to warrant treatment.

True white grub adult.

Having a 3-year life cycle, other May beetles are likely to be found as large grubs during tree planting and other soil digging. Large grubs will pupate during the summer, emerge into the soil in early fall, and spend the winter underground as adult beetles before emerging next spring to feed on tree foliage and reproduce. (Phil Nixon)

Phil Nixon

Return to table of contents