True white grub adults continue to be numerous. Although there is only one species of Japanese beetle and two species of annual white grub, there are several species of true white grub. The adults, called May beetles, typically emerge from April through June. Our most common species first appear as adults in April and May. These beetles are 1 inch long, heavy-bodied, reddish brown and dark brown. These species are still present, spending their nights feeding on tree leaves and laying eggs. These larger species typically have a three-year life cycle.
Another species of true white grub started appearing as adults in central Illinois around May 20. Some people are confusing these grubs with adult annual white grubs. These beetles are tan and about 1/2 inch long. They are slightly darker in color than annual white grub adults, but otherwise look very similar.
Unlike annual white grub adults, true white grub adults feed. They feed at night on the leaf margins of oak, ash, crab apple, and other trees, and sometimes the damage can be very noticeable. During the day, when you are seeing the damage, these beetles are hiding in the thatch of turf areas. To discover the culprits, check the trees at night at about 10 p.m. A flashlight may reveal more May beetles than you ever thought were around.
Control adult May beetles with sprays of carbaryl (Sevin) or other labeled insecticides. The larvae that hatch from the eggs being laid this spring will be controlled with insecticide applications that are ap-plied later to turf areas to control annual white grub and Japanese beetle grubs.