Overview
The black turfgrass ataenius is a small white grub that causes sporadic, severe damage to golf courses in cool-season turfgrass zones. Fairways, approaches, tees and greens all may be infested. Damage to home lawns is uncommon. The grubs commonly damage bentgrass, annual bluegrass and Kentucky bluegrass on golf courses, feeding on living plant roots as well as decaying organic matter. The black turfgrass ataenius is native to North America, where it occurs in all states east of the Rocky Mountains as well as in California, Oregon and Washington. Damage to golf courses occurs mainly in the Northeastern segment of the U.S., from New England and the mid-Atlantic states and from Kentucky and Missouri north to the Great Lakes, and along the Western Coast.
Biology
The black turfgrass ataenius has two generations per growing season in Ohio and further south, and one generation in the Great Lakes states, northern New York and New England. In the latitude of southern Ohio, injury appears around mid-June and mid-August, coinciding with the first and Black Turfgrass Ataenius second annual broods of grubs. In more northern regions where there is only one generation per year, damage shows up in July and August. Adults are small, shiny, black, 0.2-inch-long beetles with distinct longitudinal grooves on the wing covers. Newly emerged adults are reddish brown but darken in a few days. Eggs are pearly white and tiny, less than 1/32 inch. Newly hatched grubs are 1/10 inch long and hard to see. Second instars are 3/16 inch and mature third instars are 3/8 inch. Mature grubs are often mistaken for young grubs of Japanese beetles or masked chafers but the black turfgrass ataenius grub has two distinctive, pad like structures at the tip of the abdomen just in front of the anal slit. When mature, the grubs burrow down 1/2 to 3 inches into the soil and excavate a cavity in which to pupate. The pupae are small, about 3/16 inch long, with the wings and legs folded close to the body. Adults overwinter along the edges of wooded roughs or in wood lots taking shelter under leaves, pine needles, piles of grass clippings or other debris. In areas where 2 generations occur each year, adults usually begin to emerge after several warm days in late March through early May. Usually, their appearance coincides with the blooming of crocus and eastern redbud. Egg-laying begins in early May and may continue through mid-June. The beetles land on the turf and quickly burrow down. Clusters of 11 to 12 eggs are laid within small cavities near the soil-thatch interface. Eggs hatch in about a week and the grubs take about 4 weeks to mature.
Damage
Damage caused by grub feeding or predators feeding on grubs typically shows up in June. The second generation of adults emerges in late June to early July. Adults mate and lay eggs in July and early August, producing a second generation of grubs which damages turf in late August and September. In northern regions, where only one generation occurs, adults lay eggs in late June, and damage occurs in July and August. Injury appears as wilting and thinning of the turf despite adequate watering. This is a result of stunted and damaged root systems. While black turfgrass ataenius grubs are small they are often found in concentrations of 200 to 300 grubs per square foot. Birds, skunks and moles will tear up the turf to eat the grubs.
Control
Triple Crown ® Golf Insecticide applied at 35 oz. per acre using an appropriate volume of water (100+ gallons per acre) will help ensure penetration of the material down to the soil where grubs are active. Watering with ~0.25 inch of water immediately after treatment is recommended. Using lower water volumes is likely to inhibit control.