Controlling moss in putting greens - GCSAA

RESEARCHmoss. Since initial screening, we haveconcentrated on one product recentlyregistered as No-Mas, which is a 22percent active formulation of a fatty-acids a l t .Testing soap products differs fromtesting common pesticides becausethe amount of water applied as a carrierprofoundly affects the optimal rateof active ingredient. At a given rate ofactive ingredient, phytotoxicityincreases as the total volume of spraysolution decreases. After much testing,we established a rate of 0.63 gallon ofproduct/1,000 square feet applied in aminimum of 6 gallons of spray solution/1,000square feet. The same rateapplied in 12 gallons of spray solution/1,000square feet is probably optimalfor maximum moss control withoutturf injury, but it is virtually i m p o s s i b l eto achieve with most spray systems.Note: There are many soap productson the market registered for generalmoss control. They vary greatly in concentrationand recommended dilutionrates. Be sure to study specific productlabels carefully to avoid inadvertent turfinjury.Our research indicates that twoapplications applied two weeks apartgenerally achieve a high level of control.Moss kill is rapid and appears asa pronounced bleaching of mossaccompanied by a slight lightening ofturf. Turf lightening increases witheach subsequent application.Alternating soap applications with ironapplications at 0.05 pound iron/1,000square feet maintains turf color anddarkens the dead moss, improving theoverall appearance of the turf. Ironapplications can be made to soaptreatedplots the day following soapapplication. Iron will precipitate outand clog spray nozzles if it is mixedwith the soap solution.Soap treatments have been generallyeffective in western Oregon andWashington. Reports from research inCalifornia indicate poor control with winterapplications in an arid environmentwith high pH water and high pH soils. Inthe Pacific Northwest, we generallyexpect residual control during the growingseason after treatment. Long-termcontrol is not as good as for coppertreatedplots, and it appears annualtreatments will be required.Potential problemsProblems we have encounteredinclude excessive phytotoxicity whensoap applications are followed by frost.Poa annua appears to be more sensitivethan Providence creeping bentgrassunder these conditions. Occasionally turfscorching has occurred even whentreatments have been applied underoptimal conditions of mild rainy weather.Rinsing treated plots within an hour ofsoap application will generally minimizeturf scorching. Turf scorch from soapapplications is similar to a light tip burnfrom soluble fertilizer applications. Tu r frecovery is generally very rapid.Thoroughly test soap products on sitebefore using in wide-scale spray progr a m s .S u m m a r yAt some point assessing the impactof cultural practices on moss encroachmentbecomes important. The starvationtheory of putting green maintenance hasbeen followed to the point where insome cases the turf is gone and only themoss remains. Growing a dense healthystand of turf is still the best way to preventmoss from dominating turf.Superintendents should experiment withways to generate green speed otherthan starving turf to the point of thinningand mowing so low that adequate densitycannot be maintained. As long ascurrent trends in turf management continue,moss problems will persist.Once moss invades putting greens,foolproof control is impossible. T h etreatment approaches described in thispaper have provided acceptable mosscontrol in the environmental conditionsof the Pacific Northwest. According toour results, the most effective productsinclude copper hydroxide productsapplied during cool weather in sequentialapplications. Iron products appliedduring cool weather in sequential applications habeenalmoas effective, and fatty-acid soap products shogreat promise. All treatments have side effects thmust be considered. Treatments discussed in thpaper are not effective in some areas of the cout r y, and regional research is needed to fine-tutreatment programs.AcknowledgmentsPartial funding for this research has been provided by the Northwest Turfgrass Association, thOregon GCSA and Griffin LLC. Thanks to IllaheHills Country Club and superintendent BSwancutt, and Trysting Tree Golf Club and PaDoran, CGCS, for allowing us to use their facilitiefor field testing. Appreciation is also extended tnumerous undergraduate students in horticulturfor assistance in maintaining research plots.References1. Cook, T., and B. McDonald. 2002. Controllinmoss in putting greens. Turfgrass Managemenin the Pacific Northwest 5(1):4-6.2. Happ, K.E. 1998. Moss eradication in puttingreen turf. USGA Green Section Reco36(5):1-5.3. Hummel, N.W., Jr. 1988. Cultural and chemicastrategies for controlling moss (Bryum argenteum) in creeping bentgrass. A g r o n o mAbstracts 80 (Nov./Dec.):152.4. Schofield, W.B. 1992. Some common mosseof British Columbia. Royal British ColumbiMuseum, Victoria, British Columbia, Canada.Tom Cook, M.S.(cookt@mail.science.orst.edu), is an assocate professor of horticulture; BrianMcDonald is a research assistant, in thehorticulture department; and KathyMerrifield, M.S., is a senior research assistant in the department of botany and planp a t h o l o g y, all at Oregon State University,C o r v a l l i s .GCM