Many gardeners use beneficial nematodes to control turf-chomping white grubs, but the nematode species in this microscopic posse has little effect on another bane of lawns: mole crickets. Three species of mole crickets were introduced from South America around 1900, and ever since they have been happily chewing on lawns in the southern United States.
Infested lawns have historically been treated with broad-spectrum chemical pesticides. Now, thanks to years of research at the University of Florida, there's an organic alternative: Steinernema scapterisci, a nematode that's a natural enemy of one of these introduced species. Once the nematodes infect mole crickets, the pests die within 10 days, and a new generation of nematodes is released into the soil to infect other mole crickets.
Nematodes work best when applied in late September and/or October, when adult mole crickets are abundant. March and April, before the adults mate and lay eggs, is the next best application time. This species attacks only mole crickets of the genus Scapteriscus, so applications do not affect native mole crickets. Although S. scapterisci did kill small numbers of non-target insects in tests, it causes far less damage to non-pest insects, and none to earthworms and microbes, as compared to chemical controls. It also remains in the soil as long as there are mole crickets present. And because infected pests fly from place to place, they carry the nematode with them, dispersing it to new areas.
Since 1985 the University of Florida and the State of Florida have been testing S. scapterisci by introducing it throughout the state in pastures, where mole cricket populations are greatest. The nematode has remained in the soil in these areas for at least 5 years at a stretch. This bodes well that eventually it will be an established resident and will cut down on mole cricket numbers throughout the region.