Not all insects damaging turf are visible from surface scouting. We must dig into the soil to find them. White grubs, the larvae of several species of beetles (May, June, Japanese, masked chafers, etc.) and billbug larvae can be very destructive to turf without ever being seen as they feed on grass roots about an inch deep into the soil. White grubs when fully grown are whitish or grayish in color, about one and a half inches long, with brownish heads, three pairs of legs, and characteristically rest in a C-shaped position. Billbug larvae are about one-third this size and are legless. These larvae are the immature stage of a tiny weevil rather than of a beetle. Under the most severe infestations the turf can be literally lifted by hand from the soil as most all roots have been completely eaten. Often a tale-tale sign of grub damage is digging by skunks, raccoons, armadillos, and moles as they forage for the grubs.
Now is a good time to scout for grub damage and control them as there is still time for the turf to recover from their injury before winter. To determine if you have a grub problem cut several 1 x 1 foot square samples of turf 1-2 inches deep from your lawn and crumble the soil from the turf examining for active grubs. If you find and average of three to five grubs per square then you should seriously consider treating with an appropriate insecticide. When treating with insecticides if the soil is dry water before applying and again after treating. For more information on white grubs and billbug larvae and insecticides recommended for their control refer to extension publication #2331 “Control Insect Pests in and around the Home Lawn”. This publication can be downloaded or a copy can be obtained from your local extension office.
Dr. Wayne Wells is an Extension Professor and Turfgrass Specialist. His mailing address is Department of Plant and Soil Sciences, Mail Stop 9555, Mississippi State, MS 39762. firstname.lastname@example.org