Be watchful on golf courses for high populations of black turfgrass ataenius, Ataenius spretulus. They appear as small white grubs feeding in the root zone of the wettest portions of the course: greens, tees, around the aprons of greens where water collects after irrigation and in swales of fairways where water tends to puddle. The grubs are white and C-shaped, with six legs and a brown head. They appear more slender than other white grubs and are about 1/4 inch long when full grown. Although small numbers of these white grubs are common in lawns, there are unlikely to be enough to cause damage unless the turf is very highly maintained and watered heavily.
We are nearing the end of the first generation of this insect, meaning that the grubs are close to 1/4 inch long and are eating more turf roots than when they were younger. Populations of 50 or more per square foot will cause turf to wilt and turn brown. The turf will pull up easily to reveal the grubs in the root zone.
These larvae pupate to emerge later in July as 1/4-inch long, black to brownish, cylindrical beetles. The beetles are easily seen in clippings baskets of greens mowers. They mate and lay eggs, which hatch into another generation of larvae that feed through the rest of the summer. By fall, they pupate and emerge as adults who fly to wooded areas, where they overwinter under fallen leaves. The adults fly to the greens in the spring to produce another generation of white grubs.
Applications of trichlorfon (Dylox) at this time will provide control of the white grubs in about 3 days. The second generation of black turfgrass ataenius coincides with the larger white grubs, including Japanese beetle, southern masked chafer, and northern masked chafer. Applications of imidacloprid (Merit) or halofenozide (Mach 2) during July will provide control of all four species. Neither Merit nor Mach 2 is likely to provide quick control of mature ataenius grubs, nor will Dylox applied at this time provide control of white grubs that hatch later.