Chemical and Cultural Controls for Moss, Bryum argenteum on Putting Greens

March 16, 2005

Summary: In two trials conducted at Friendly Hills Country Club, Whittier, CA, a variety of herbicides, fungicides, surfactants, algaecides and fertilizers were tested for their ability to decrease infestations of Bryum argenteum (silver thread moss) on a heavily moss infested poa/bent putting green. Key findings include:

• Moss was positively identified as Bryum argenteum on the basis of leaf cell architecture (upper leaves with rhomboid-hexagonal cells) and the silvery-white color of the plants. A blue-green algae was consistently found in association with the moss.
• The most effective treatments contained chlorothalonil (Daconil 2787 and Daconil Ultrex) or quaternary ammonia (RD-20), with up to 80% moss control achieved by the end of the 3 month trial. No phytotoxicity was observed with these treatments. The efficacy of these products may be related to their algaecidal activity.
• Treatments which injured turfgrass (Lesco Iron Plus fertilizer, Ronstar 2G and Dimension) resulted in an overall increase in moss by the end of the study. Although these treatments initially injured the moss plants, lack of competition of from injured turf appeared to allow the moss to expand its invasion into areas of thinning and/or damaged turf.
• Some treatments which were reported to control moss at other locations (Ferrous sulfate, Ultra Dawn, Subdue 2E mixtures) had no effect on moss populations in this trial. This may be due to the fact that all treatments were made using broadcast applications (2 - 4 gallons spray solution/1000 sq ft), rather than spot treatments. In a follow up trial investigating the use of Ultra Dawn applied as a spot treatment, drench-type applications (4 oz/gallon UltraDawn, applied in 80 gallons spray solution/1000 sq ft) were found to be extremely effective for control of moss.
• If moss infestations are heavy, gradual removal of moss, as was observed using chlorothalonil or quaternary ammonia, is the most desirable strategy, since it avoids the appearance of large areas of dead or dying moss. However, if moss infestations are light, spot treatments with products that rapidly kill the moss may be the most effective strategy.

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Principal Investigators: Wendy Gelernter, Ph.D. and Larry J. Stowell, Ph.D., CPPP, CPAg

Cooperator: David Michael, Friendly Hills Country Club

Sponsor: Rohm and Haas, Zeneca, PACE Consulting