We are receiving reports of white grub damage to turf in east-central Illinois. We have been surprised that damage has not been reported earlier considering the size of the grub adult flight and turf moisture conditions during egg laying. Realize that the grubs are getting larger, resulting in each grub eating more. Typically, fall rainfall helps the turf roots grow faster than the grubs can eat them, but a dry spell can make the turf susceptible to damage.
One acceptable strategy to avoid grub damage at this time of year is irrigation during dry periods. This keeps the grass roots growing fast enough to feed both the plants and a marginally damaging grub population.
Insecticides applied should be those that act quickly. Trichlorfon (Dylox, Proxol) kills grubs in 3 days but may break down in 5 to 7 days. Bendiocarb (Turcam) and diazinon are also effective. Remember that diazinon canít be applied to golf courses and sod farms. Diazinon also takes up to 3 weeks to kill the grubs, although apparently the grubs donít feed during that time. At this time of year, the grubs move vertically through the soil in relation to moisture. If the turf area is dry, irrigate a day or two before insecticide treatment to bring the grubs up into the root zone where they can be controlled.