Dollar spot is one of the top turfgrass disease threats on golf courses in the Midwest and Northeast. “And it’s not going away,” said Todd Hicks, a plant pathologist at The Ohio State University.
Considering the threat of fungicide resistance among the available active ingredients on the market to control dollar spot, what golf course superintendents need is a new mode of action to help control the disease and avoid resistance, Hicks added, noting that a new fungicide from Nufarm and Valent U.S.A. will help fill that void.
The fungicide, Pinpoint, is scheduled to be approved for use on golf courses by the U.S. Environmental Protection Agency (EPA) this month. Its active ingredient, mandestrobin, acts as a mitochondrial respiration inhibitor and disrupts the energy cycle in the dollar spot pathogen, known as Sclerotinia homoeocarpa. Mandestrobin exhibits preventive and early curative activity.
Pinpoint, which features low use rates, is the only strobilurin on the market for dollar spot control. While other classes of strobilurins have proven to delay dollar spot and show a minor reduction of the disease, no strobilurin has shown the control that mandestrobin offers, Hicks said during a roundtable discussion held recently at Ohio State that focused on Pinpoint and dollar spot control.
Jason Fausey, director of technical services for Nufarm’s turf and ornamental division, said researchers discovered that mandestrobin has “a unique property for a strobilurin fungicide in that it provides strong control of dollar spot.”
“We happened to find a strobilurin that targeted this pathogen,” Fausey said. “We were fortunate.”
Hicks said “it was incredible to see” a strobilurin that acted alone to control dollar spot. He noted that some combo products contain a strobilurin and are labeled for dollar spot control, but it is not the strobilurin in the combo products that is controlling dollar spot.
Pinpoint can be used in the spring, summer and fall. It can also be used in the heat of the summer, when superintendents are forced to back off using DMIs (demethylation inhibitors) because they can damage turf in such conditions.
Hicks said Pinpoint is good news for superintendents looking for “another product in the toolbox” to control dollar spot as well as reduce fungicide resistance. It can be used in rotation with sterol biosynthesis inhibiting (SI) products, chlorothalonil and other contact fungicides.
Because of use-rate limitations, which Hicks said could increase, superintendents should find Pinpoint a welcome addition to their fungicide programs. More chemistries are being looked at by the EPA, which Hicks said could lead to some of them being reduced as far as use rate or even eliminated. So having another mode of action to control dollar spot is vital for superintendents to avoid resistance issues.
Hicks noted that some superintendents aim to control resistance by using reduced rates, which is not a good idea. “I’m not a believer in reduced rates,” he added. “If I’m going to fight you, and I have the chance to give you a left hook and knock you out, that’s what I’m going to do.”
With Pinpoint’s new mode of action, superintendents don’t have to reduce rates of other active ingredients, such as DMIs, SIs and chlorothalonil, Hicks added.
Joe Rimelspach, a plant pathologist at Ohio State University, said dollar spot has become a threat throughout the season, which wasn’t the case a decade ago. “It’s very widespread,” he added. “We don’t understand the pathogen very well yet, which is amazing for all the years we have been studying it.”
Rimelspach said some superintendents claim that they have “a new pitted dollar spot” on fairways, but that’s not the case. “It’s just that they have never controlled it,” he said. “The [dollar spot] has been slowly chewing the turf away. With a long-term infection, there’s a slow and long process to recovery.”
Pinpoint’s label states that superintendents can make up to five applications a year. While Pinpoint controls other diseases, Fausey said Nufarm and Valent U.S.A. will mainly promote Pinpoint’s ability to control dollar spot.