Grubs

Grubs are the most common insect pests of lawns in the area. White grubs will feed on most species of grass but damage is most likely to appear in bluegrass and tall fescue lawns. Grubs are C-shaped and vary from white to off-white in color. They have a brown head, six legs immediately behind the head and a dark area on the rear end.

Damage from grubs usually appears in late summer, from mid August on. There may be the appearance of an off colored spot in the lawn. Upon closer inspection the off color might be due to wilted grass or dead grass. Grass vigor is reduced as the grubs feed on the root system. Normally with grub damage the grass plants can be easily pulled up. Moles and skunks might tear the sod while searching for tasty grubs. Entire sections of sod might roll back with little effort leaving the C-shaped grubs lying exposed on the soil surface.

There are two main types of grubs that may damage lawns in this area, the Southern Masked Chafer (annual grub) and the May/June Beetle (three year grubs). The Southern Masked Chafer or annual grub is the most common.

Merit (Imidacloprid) and Mach 2 (Halofenozide) are insecticides that have longer residuals than the other products. They should be applied anytime from late June to mid-July for the Southern Masked Chafer, rather than late July or early August. If the three year grubs are of concern, apply the Merit in June. One application should give season-long control for both type of grub. Mach 2 is not as long lasting as Merit and should not be applied before late June if control of the annual grub is desired.

Dylox is recommended if the preventative treatment timing is missed. Apply Dylox in early August for control of the one year grub. Insecticides applied after late August for the Southern Masked Chafer will not be as effective.

Effectiveness of the grub control can be improved by reading and following all label instructions. Most products for the homeowner are in a granular form. Before applying the products make sure there is good soil moisture either from natural rainfall or irrigation. After applying, most products recommend that they be watered into the soil.

Dennis Patton, DPatton@oznet.ksu.edu
County Extension Agent, Horticulture
Johnson County, Kansas
Kansas State University Research and Extension