Black turfgrass ataenius is a turf-attacking grub that overwinters as adult beetles in debris in low-lying areas. On golf courses, this habitat is commonly provided by tree plantings between fairways. Because the fairways are elevated to provide drainage, the runoff water tends to accumulate between fairways. Trees are typically planted between fairways to provide visual screening from golfers on adjacent fairways and to deflect balls. Fallen tree leaves are frequently allowed to remain in these areas or in nearby natural areas, providing excellent overwintering locations for the beetles.
The black turfgrass ataenius adult beetles fly in the spring to the most heavily irrigated portions of the golf course, primarily the greens, tees, and low-lying areas of fairways. They are about 1/4 inch long, shiny black, cylindrical beetles and are noticeable in the clippings baskets of greens mowers. Eggs hatch about 2 weeks after the beetles migrate to turf areas, which is when insecticidal control should be applied. This is typically when bridalwreath spirea, vanhoutte spirea, is in full bloom.
The resulting larvae are white grubs that appear similar to other turf-feeding white grubs except that they stay small, with fully grown grubs being only about 1/4 inch long. They also appear to be more slender than other white grubs. They have no raster pattern, arrangement of heavy hairs or light spines, on the underside of the end of the abdomen. Instead, they have two large pads in that area.
Feeding by the first generation continues through the spring, with pupation occurring in late June to early July. A second generation of beetles emerges shortly thereafter to lay eggs for a second generation of larvae. These larvae feed through the late summer into early fall and then pupate. Adults emerge from these pupae in the fall and fly to damp leaf litter to overwinter.
Damage is most likely to occur in the wettest areas of the golf course, where the adults are attracted. Greens, tees, and swales in fairways are likey to have wilted, brownish turf that can easily be pulled up. The small, black turfgrass ataenius grubs are located in the root zone and are easily seen when the turf is pulled back. If scouting for ataenius grubs, 50 or more grubs per foot square are enough to cause damage.
Keep an eye on the clippings baskets of greens mowers to determine when the adult beetles fly onto the course and to determine, in relative terms, the size of the population. Mark the date when the beetles were numerous and apply imidacloprid (Merit) or halofenozide (Mach 2) about 2 weeks later, which should be when vanhoutte spirea is in full bloom. This is occurring in southern and will soon occur in central Illinois. Treatment should occur in late May in northern Illinois. If beetle numbers were small, scout for the grubs late in vanhoutte spirea bloom by cutting through the turf and pulling it back. In irrigated turf, the grubs should be in the upper root zone.
Imidacloprid and halofenozide are persistent enough that this spring application will control not only first-generation black turfgrass ataenius but also second-generation black turfgrass ataenius, Japanese beetle, and masked chafer grubs in August. About 15 percent of the time, control will not be achieved in August, so scout for grubs at that time. If damaging numbers of grubs are found, apply trichlorfon (Dylox) as a rescue treatment. Trichlorfon is also recommended as a rescue treatment if damaging numbers of first-generation black turfgrass ataenius grubs are found in June.