San Diego – Silvery thread moss (Bryum argenteum) is the No. 1 problem on many Poa and bentgrass greens largely because many products that control moss also control turf, according to Wendy Gelernter, Ph.D., research director for the PACE Turfgrass Research Institute.
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Lack of turf-safe moss-control products and other turf management topics were discussed June 27 at the ninth annual PACE Turfgrass Research Seminar in San Diego. More than 100 golf course superintendents and turf managers attended the 10-session seminar that also covered the role of reduced phosphorous levels in suppressing Poa annua invasion of bentgrass greens, the activity and recommended use patterns for newly registered pesticides, and wetting agent studies. Presentations and handouts from all the sessions are available to PACE members at www.paceturf.org. Nonmembers may sign up at the site for a free trial membership.
Because of their potential to harm turf, moss-control products need to be selected carefully, Gelernter says. Products that are effective for moss but have the potential to injure turf include iron-based products such as ferrous sulfate, copper hydroxide (Junction) and sodium carbonate peroxyhydrate (Terracyte).
Despite the phytotoxicity potential of these products, however, some superintendents have successfully integrated them into their moss-control programs.
“But remember to test anything new on a small area first and incorporate products into your program gradually,” Gelernter says.
Research trials from around the country confirm that the two most effective moss-control products with the least phyto-potential are chlorothalonil (Echo, Daconil, Manicure) and carfentrazone (QuickSilver). Chlorothalonil has been labeled for moss control on greens for several years, but the Environmental Protection Agency is reviewing an expanded label request for carfentrazone that would include greens. Gelernter says higher application volumes (greater than 2 gallons per 1,000 square feet) and repeat applications are necessary with most products for best results.
“One of the most important, and also most overlooked, aspects of moss control is the follow-up,” she says. “After the moss has died and there is a bare area on the green, it is absolutely critical to encourage turf growth so it wins the race to fill in the bare spot before the moss does. This means providing the turf with enough water and nutrients – basically treating it as though it were growing in for the first time – to give it the edge over moss.”
Larry Stowell, Ph.D., also a PACE research director, discussed the role of several nutrients in pest management, including the role of reduced phosphorous levels in suppressing Poa annua invasion of bentgrass greens. Stowell showed that there are cases in which low phosphorous (below 20 ppm as measured using the Mehlich III extraction) appears to have suppressed Poa invasion, but he cautioned that there’s a risk involved when pushing phosphorous levels so low that turf health is threatened.
Stowell also spoke about the role of nitrogen fertilization in management of anthracnose (Colletotrichum graminicola). Recent research from Rutgers University shows that frequent, low doses of nitrogen are important in helping Poa annua plants fight off fungal infection.
“Based on the research, it appears that application of 0.1 pounds of nitrogen per 1,000 square feet per week during the active growth period for Poa annua can be beneficial,” he says. “The growth regulator, Primo, also has been shown to aid in anthracnose suppression when applied at a rate of 0.125 ounces per 1,000 every 14 days during the same time period.”
Speakers Gelernter and Stowell, as well as Frank Wong of the University of California, reviewed the activity and recommended use patterns for newly registered products, including fungicides such as Endorse and Emerald, insecticides such as Allectus and Arena, and herbicides such as Velocity and Revolver.
Shoumo Mitra, Ph.D. of California Polytechnic Institute in Pomona, reviewed the results of the wetting agent studies he conducted as part of the nationwide Golf Course Superintendents Association of America-U.S. Golf Association wetting agent project. Mitra’s data showed that in both years of the study wetting agents Brilliance, Cascade Plus, Lesco Flor, Primer Select and TriCure significantly reduced hydrophobicity compared with the control. However, Mitra says there was some degree of phytotoxicity associated with most of the products, with Cascade Plus producing the most significant levels of turf damage.
