May 2, 2008

Although earthworms are beneficial in most agricultural systems, they can wreak havoc on meticulously managed, closely-mowed sports turf. Large numbers of earthworm castings deposited on the surface can render golf putting greens and croquet courts virtually unplayable, and excessive earthworm burrowing activity can cause root desiccation and turf thinning on athletic fields. The castings interfere with turf maintenance by dulling mower blades, preventing a clean cut. When compacted by foot traffic, carts, or mowing equipment, castings can create silver-dollar sized mud spots that can critically damage the turf underneath.

Casting occurs when earthworms ingest soil and leaf tissue, then emerge from their burrows to deposit the fecal matter, or casts, as mounds of soil on the turf surface.

“Earthworms are extremely beneficial, especially in our lawns, and we’ve shown how important they are in aerating the soil and breaking down thatch,” said Daniel Potter, University of Kentucky College of Agriculture entomology professor. “But earthworms can be a real burden to turf managers and players. You don’t want to see Tiger Woods having to putt his golf ball at the Master’s through a big series of muddy castings all over the surface.”

Potter and collaborators including Carl Redmond, UK entomology research analyst and David Williams UK turf grass specialist are trying to find an ecologically responsible way to manage earthworms and castings in fine turf. Last year, he was a keynote speaker at an international symposium on science of sport turf management in China held in advance of the 2008 Beijing Olympic Games. Potter talked to researchers at the symposium about the earthworm dilemma because it’s also an issue on some Olympic event sites.

“I asked how they deal with this earthworm issue on golf courses and other sites in China,” Potter said. “They told me about use of a natural by-product made from a plant related to tea. They make oil from the seeds of this plant, much like we would do with canola oil and soybean oil. What’s left over after the seeds are squeezed is a husk that contains a natural substance that’s irritating to earthworms.”

Potter said the Chinese turf managers apply the substance to the turf and then water it into the soil. In response, the earthworms come out of the ground and then turf managers rake them or hose them off of the playing surface, thus eliminating the casting problem.

“It sounded interesting, and I asked them to send me a sample, and that’s what we are evaluating out here at Spindletop (Research Farm),” he said. “It’s a natural, botanical product from the seeds of a food product, and it’s working extremely well. When we apply this product in a small amount and then apply a little bit of irrigation to the putting green, the earthworms come boiling out of the ground.”

Potter and his associates are trying to determine the earthworms’ survival rate and decide whether or not they can transplant them to out-of-play areas where their activities are beneficial. He said they are also counting the castings to see how long the benefit lasts.

“We’ve had our people who mow the putting greens out here at Spindletop comment on how they wish they had this stuff,” Potter remarked. “They say the castings are greatly reduced and the quality of the turf is improved. I think the benefit here is that we have a natural product that we may be able to use to manage earthworms in an environmentally responsible way.”

Potter said earthworm management is a problem on golf courses worldwide. Currently no pesticides are approved to manage the problem in the United States. For the most part, turf managers are currently dealing with it by brushing the castings off the course with brooms or similar tools, which is labor intensive and not really a long-term solution. But, there are no published studies on this management approach.

Although the natural product is not yet commercially available, Potter said since it’s a byproduct of food manufacturing, he doesn’t think it will be very expensive at all.

“I would expect a superintendent could buy some 50-pound sacks of this and not have to pay much more than he or she pays for mulch,” he said. “We just use a very small amount. It looks like rabbit food and the pellets decompose in a day or two.”

Potter believes that golf course managers will be the primary users of the product and it would also be useful for sport fields where earthworm castings can muddy and smother the turf.

“We certainly wouldn’t use this product where we want to conserve earthworms like home lawns, where they are so beneficial,” Potter emphasized.

The research phase of the project has shown success, so Potter is currently interacting with researchers in China as well as a commercial company dealing with specialty turf products. Since the product is natural, Potter said he expects the registration process to be accelerated. This study is a small part of ongoing research efforts by Potter, Williams and other UK turfgrass scientists to develop environmentally safe solutions for insect pests, weeds and diseases of lawns, golf courses and sport fields.

An upcoming UK College of Agriculture Field Day at Spindletop Research Farm on June 12 will highlight a variety of ongoing turf research projects, as well as equine, forage and crop research. The field day is titled “Agriculture in a New Bioeconomy.” The event begins with registration and exhibits at 2 p.m. Field clinics/workshops begin at 3 p.m. and continue through 5:30 p.m. Field tours will take place from 6 to 8 p.m. Contact your local county extension office for more information or Field Day Chairman J.D. Green, at 859-257-4898, e-mail: jdgreen@uky.edu.

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