Watch Out for Late Season Grub Activity

By Pat Gross, Director
Octber 22, 2004

A number of courses have experienced turf damage in recent weeks due to late season grub activity. Various species of adult beetles have been very active on greens and fairways including black turfgrass ataenius, aphodius, chafer, and a relatively new species in our area, billbugs. The adult beetles typically lay eggs in the late spring and early summer, but this year, the activity has been more prominent in the early fall. Birds, skunks, and fox have torn up large areas of turf to feed on the grubs causing significant damage to greens and fairways. Healthy turf can tolerate a moderate to low threshold of grub feeding without impacting playing conditions. The question then becomes how much is too much? If the damage caused by the animal feeding is extensive, it may be necessary to make a spot application of an approved insecticide to the affected fairways or greens.

It is important to note that grub damage on greens often displays symptoms similar to localized dry spots. Maintenance personnel should check potential dry areas for grubs before assuming that the symptoms are due to a lack of water. To scout for grubs, it is best to make an "H" shaped slice, peel back the flaps of turf and look for the small grubs in the top ¾" of the soil and thatch. The person in charge of changing holes in the morning also should be on the look out for grubs in the hole plugs. Frequent monitoring during this time of the year can help reduce the damage caused by grubs and the larger animals that feed on the grubs.

Pat Gross is the Director of the Southwest Region of the Green Section.