Scientist advises greenkeepers to protect golf courses against bermudagrass stunt mites
FLORENCE – Double, double toil and – a witch’s brew of troubles.
This take on the witches’ chants found in William Shakespeare’s Macbeth may be the cry of greenkeepers throughout the southern United States if their golf courses fall prey to bermudagrass mites. Juang-Horng “JC” Chong, an entomologist at the Clemson University Pee Dee Research and Education Center in Florence, said the mites, also known as bermudagrass stunt mites, are becoming an “increasing problem” on golf courses from Texas to South Carolina.
“I usually have recommendations, if not solutions, to most insect problems,” Chong said. “But for the past few years, the bermudagrass stunt mite is one insect that has made me have to stop and think of the best method to use to control it.”
Bermudagrass stunt mites are very small and are whitish cream or translucent in color. A large number of mites feed under the leaf sheath, causing stunted internodes and a typical “witch’s broom,” or rosetting. Because of their small size, color and habit of feeding on the underside of a leaf, Chong said the mites are extremely difficult to see even with magnifiers.
“The witch’s broom damage is a more reliable means of diagnosing a bermudagrass stunt mite infestation,” he said. “But, it may take a few years before witch’s brooms are detected and by that time a lot of damage may already have been done.”
Witches’ brooms are formed from shoots with short internodes that can look like a bundle of twigs or a witch’s brooms. Formation of witches’ brooms is permanent and infestation of mites in turfgrass causes the grass to die, leaving unacceptable bare spots on golf courses. The costs for repairing severly damaged golf courses can run in the hundreds of thousands of dollars, Chong said.
“The damage appears to be most severe on slopes and at the edges of bunkers, indicating a correlation between severity of the damage and soil dryness,” Chong said.
In the past, the bermudagrass stunt mites have just been an occasional pest of bermudagrass. Now, however, the insect seems to have become an increasing turfgrass problem. Chong credits the recent gain in the insect’s notoriety to several reasons. The first reason could be that golf course superintendents could be better educated now as to the damages caused by the mites. Other reasons could be the reduced amount of rainfall in recent years and changes in irrigation practices, as well as changes in mowing, pesticide use or pest-management practices.
Cultivar selection is another factor to consider when it comes to managing bermudagrass mites. For instance, the popular fairway cultivar Tifway is very susceptible, Chong said.
The recent flare-up of bermudagrass mites could be a combination of any of these factors, he said.
Because so little is known about this pest, Chong said there are no effective management programs for use in controlling the pest at this time. As with any management program, the first step to take is determining the cause of any detected damage. If witches’ brooms are found, Chong said to collect live samples, seal them in plastic bags and send or bring the bags to the local Clemson Cooperative Extension Service offices for identification by Extension specialists.
Currently, there is no effective pesticide to use against the bermudagrass mite, Chong said. Diazinon is the most effective active insecticide to use against the bermudagrass mite, but its uses have been banned by U.S. Environmental Protection Agency due to its high toxicity. Use of two other pesticides, chlorpyrifos and dicofol, are restricted on golf courses. The pesticide abamectin can just be used to control nematodes on putting greens, Chong said.
Although there are no effective chemicals to use in controlling the bermudagrass mite, using cultural management practices to control the mite may be an option, Chong said. Because damage from the bermudagrass mites is most noticeable on longer stems, lowering mowing height, as well as vacuuming clippings may help remove infested stems. Because the mites can “hitch” a ride on clippings, it is important to sanitize mowing equipment after working in an infested area, Chong said.
While these cultural practices may help control bermudagrass mites, more research is needed to determine just how effective these practices are and on developing bermudagrass cultivars that are resistant to bermudagrass mites, Chong said.
“We have not made much progress in managing the bermudagrass mite in the past 30 years,” Chong said. “In fact, we may have taken a few steps backward by phasing out several effective pesticides. Our actions, or lack of actions, have created a witch’s brew of problems that demand more attention and more resources. I am a firm believer that, regardless of how great the challenge may be, our drive and ingenuity can help us find a solution that will benefit all.”
For more information on this and other insect pests, go to www.clemson.edu/extension/.