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Identification

Adult beetles are shiny, jet black, 1/5 inch (0.5 cm) long, with club-end antennae and parallel grooves on the wing covers. They may be seen walking across turf. Larvae are very small, C-shaped grubs with a scattered pattern of bristles on the last abdominal segment and a pair of pads at the tip of the abdomen. These characteristics help distinguish larvae from other turfgrass pests.

Hosts

Annual bluegrass (a common weed in turf), creeping bentgrass, Kentucky bluegrass, perennial ryegrass

Damage

Larvae feed on roots, causing irregular patches of brown or dead turf. Damaged turf can appear drought stressed, and the problem may be confused with damage due to turf root diseases such as summer patch. Turf with extensive root damage can be easily peeled off the soil. This pest is primarily a concern in golf courses, but occasionally invades home lawns.

Monitoring information

Look for ataenius grubs when you observe damage or about 2 weeks after adults are seen. Dig around roots for very small, whitish, C-shaped grubs up to 1/3 inch (0.8 cm) long with 6 legs and reddish heads. Inspect outdoor lights around dawn for shiny black adults, 1/5 inch (0.5 cm) long. Don’t confuse ataenius adults with similar looking predaceous ground beetles or Aphodius beetles.

Management

Black turfgrass ataenius grubs cause damage mostly in turf that is stressed by overwatering, high temperatures, heavy traffic, or too-low mowing height. Improve root growth as much as possible to allow turfgrass to withstand grub feeding by aerating, raising your mowing height, and following recommended irrigation practices for your turf species. If you find more than 40 grubs per square foot, you may need to treat with an insecticide. Beneficial nematodes are effective when grubs are active.

For more information on lawn insects, refer to:
Pest Notes: Lawn Insects