August 22, 2017
During the U.S. Open held this summer in Erin Hills, Wisconsin, some of the world's top golfers competed for a shot at becoming the 2017 champion (won by Brooks Koepka). The course's meticulously groomed putting greens and fairways—like those of so many other golf facilities—are an inspiration to lawn-care enthusiasts near and far.
But professional golf course superintendents and lawn-loving homeowners alike face a common foe: chubby, C-shaped pests called "white grubs," which eat the turf grass roots. Unchecked, they cause brown spots or barren patches that mar the turf's aesthetic value and even playability.
Robert Behle isn't an avid golfer, and you won't find him competing with his neighbors for the best-looking lawn. But he does know a thing or two about insects—and even more about controlling them using their natural enemies. An Agricultural Research Service (ARS) entomologist, Behle specializes in ways to formulate naturally occurring fungi and other microorganisms into bio-based pesticides.
In fact, he and Purdue University colleague Doug Richmond recently finished a three-year project funded by the U.S Golf Association (USGA) to evaluate the potential of the fungus Metarhizium brunneum to kill white grubs, the larval stages of Japanese, June, and other scarab beetles. The practice, known as "biological control," is one that's already found its way onto some golf courses. Indeed, a 2015 survey by the Environmental Institute for Golf found that 42 percent of 27-plus-hole golf facilities sometimes or frequently use biocontrol in their pest management practices.
The researchers used an ARS patent-pending process called "liquid culture fermentation" to mass-produce the fungus and turn it into clay granules, which they applied at different rates to grub-infested turf grass plots at Purdue University.
When they rolled back patches of the turf, a grizzly sight awaited them. Depending on the rates applied, 50 to 70 percent of the grubs lay dead beneath the soil, covered in a fuzzy growth that confirmed the fungus had infected and killed them—typically 7 to 10 days after exposure.
An insecticide applied to different plots worked even faster, killing 95 percent of the grubs. However, when used in the fall, the chemical had lost some of its "punch" against larger-sized grubs compared to the fungus, which worked better with the cooler temperatures.
The findings, which the researchers published in a USGA annual report , could help golf course superintendents identify ways to use the fungus as part of an integrated pest management (IPM) approach, which combines judicious insecticide use with cultural, biological and other controls.
Golfers needn't be distracted by the prospects of this biocontrol fungus quietly working underfoot, though. Its absolute preference for infecting white grubs and other insect turf eaters means people, pets and wildlife won't suffer the same fuzzy fate as these pests.
Posted by Jan Suszkiw, Public Affairs Specialist, Agricultural Research Service