Controlling moss in putting greens - GCSAA

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RESEARCHputting greens probably reflects recenttrends in putting green culture, includingextremely low mowing, minimal nitrogenf e r t i l i z e r, increased use of sand growingmediums, intense sand topdressing andloss of mercury fungicides, which werehighly toxic to moss. It occurs on bothbentgrass and Poa annua greens but isby far a bigger problem on sand-basedbentgrass greens. We have found significantpopulations on first-year greenson new golf courses. It often shows upfirst in weak areas such as ridges andmounds where grass is thin because ofscalping or drought stress. It aggressivelycolonizes low, wet areas andthrives on soil-based greens with shallowlayers of sand built up by topdressing.Research strategiesOur research, conducted at OregonState University, primarily concerns mossgrowing in creeping bentgrass greens,and the following results are from workdone entirely on Providence creepingbentgrass in sand-based growing mediumsand SR 7200 velvet bentgrass growingon soil and topdressed with sand. Todate we have concentrated on large-scalebroadcast treatments rather than spottreatments directed at localized infestations.Most of the chemical treatmentshave been applied during fall and winterwhen temperatures range from 40 to 65 Fand moisture from precipitation is common.Soil pH in the area is typically 5.5 to6.5, and salt levels are very low.Early screening trialsAfter unsuccessful attempts by superintendentsto try iron products at normalputting green rates, we screened a widerange of products by applying each at avariety of rates from low to very high.Products included in our experimentswere selected because reports in the literatureindicated that they controlled moss orthat they were being applied on puttinggreens in an attempt to control moss. Weeliminated products that caused turf damageand others that had no effect on themoss. The following products were testedand eliminated from consideration.Copper sulfate. Copper sulfate is notlabeled for moss control. In our tests, itRelative residual moss control in plots treated the previous winter with junction ( Copper Hydroxide + Mancozeb),No-Mas(fatty acid soas),daconil fungicide,and an untreated check plot.caused severe turf injury at rates necessaryfor moss kill. Caused root stunting int u r f .Copper soaps. Copper soaps are notlabeled for moss control. We found themto be highly effective moss killers but toxicto turf, even at moderate rates.Zinc sulfate. These products are notlabeled for moss control in putting greens,although some retail products are labeledfor moss control in lawns. A c c e p t a b l emoss control but caused significant turfinjury at marginally high rates.Daconil Zn and Daconil Ultrex. Bothproducts are labeled as fungicides andnot for moss control. They were ineff e c-tive in controlling moss under low-temperatureconditions. Some reportsindicate control at higher summer temperatures.No undesirable side effects onturf even after 15 repeat treatments.Dawn Ultra. Dawn Ultra was ineff e c-tive on moss at rates ranging from 2 to 8ounces of product/1,000 square feetwhen applied during cool, wet conditions.Dawn Ultra is marketed as a dishwashingliquid, and certified commercial pesticideapplicatorscannotlegally apply Dawn Ultra for moss control.Doing so would be the same as applyingan unregistered pesticide.Advanced screeningThe next phase involved further testingof products that showed promise formoss control and caused little or no turfi n j u r y. Products included ferrous and ferricsulfate, fatty acid soaps and copperhydroxide products. All of these havebeen tested repeatedly at several ratesand with varying numbers of repeat applications.Research results for these productsare summarized below.Iron productsNormal rates of iron for turf colorenhancement are about 0.03 poundiron/1,000 square feet. Under cool, wetconditions, rates of 0.15 to 0.20 poundiron/1,000 square feet controlled mossmarginally without injury or blackening ofProvidence creeping bentgrass turf.Ferric sulfate is more effective at killingmoss than ferrous sulfate, but bothrequire a series of five to seven treatmentsapplied at two-week intervals. Tu r fis exceptionally dark green during treatment.We achieved up to 90 percentmoss control with both ferrous and ferricsulfate, which is encouraging but not aseffective as we would like. Annual applicationsmay be necessary, and control isnot always consistent. Field test resultshave been mixed, with most tests usingferrous sulfate and reporting fair to goodGCM
RESEARCHcontrol.Copper hydroxide productsMost of our research has used Kocide2000, which is straight copper hydroxide,and Junction, which contains both copperhydroxide and mancozeb fungicide. Bothproducts show similar activity and areregistered for moss control.In western Oregon, we achieved eff e c-tive moss control with five to seven treatmentsapplied at two-week intervals atrates of 0.1 to 0.15 pound copper/1,000square feet during cool wet weatherbetween October and March. Moss injuryoccurs gradually and is progressivelygreater with each application. Am i n i m u mof five treatments is needed to prevent themoss from growing back. We normallyplan on six to seven treatments. Duringtreatment turf darkens slightly but not asdramatically as with iron products.Darkening continues into the spring evenafter treatments have been completed. Asingle treatment series of seven applicationshas provided one to two years ofacceptable moss control in our locala r e a .Potential problemsUsing copper hydroxide for mosscontrol raises several concerns. One isthe potential buildup of copper in the rootzone, which may stunt root growth. Inearly screening trials, applying the equivalentof 6 pounds of copper/1,000square feet over a one-year periodstunted root growth. Although this is fourto seven times the amount that would beapplied in a normal treatment sequence,it is still cause for concern. We nowadvise applying copper treatments nomore than two years in a row at a totalrate of 1.0 pound copper/1,000 squaref e e t / y e a r. However, surface soil levels ofcopper as high as 42 ppm have beennoted without any apparent root stuntingunder our climate conditions.Copper-induced iron chlorosis isanother concern with copper hydroxideproducts. The problem was firstobserved where copper treatments hadbeen applied on golf courses for twoconsecutive years. No problemsoccurred the first year, but severe chlorosisdeveloped the second year.Symptoms were worse on weak orshaded greens. Greens in full sun werenot affected. We concluded that thesymptoms were not phytotoxicity but ironchlorosis. Further experiments in whichwe alternated copper treatments with0.05 pound iron/1,000 square feet duringa sequence eliminated signs of chlorosis.Current recommendationsCurrent recommendations are toapply copper hydroxide products duringcool weather at 0.10-0.15 pound copper/1,000square feet at two-week intervalsfor a total of five to sevenapplications. If signs of iron chlorosisoccur during or after treatment with copperhydroxide, apply iron at 0.05 poundiron/1,000 square feet as needed toeliminate chlorosis. Iron can be tankmixedwith copper hydroxide if constantagitation is maintained in the spray solution.A minimum spray volume of 2 gallons/1,000square feet is suggested.Please note: In areas with hot, stressfulsummers where summer root loss iscommon, conduct thorough on-site testingon nursery turf to make sure coppertreatments do not cause root stuntingand thus increase the chance of turfloss during the summer.Superintendents who have usedcopper hydroxide products havereported mixed field results. In westernOregon and Washington and parts ofCalifornia, superintendents havereported excellent and fairly long-lastingcontrol without deleterious effects toturf. Other superintendents havereported short-term or partial control,and in parts of California, some havereported no control at all. Factors thatmay affect control are lack of extendedperiods of cool temperatures, lowhumidityenvironments, high soil andwater pH, and elevated salt levels in irrigationand/or spray solutions. Coppermay not be effective in these situations,but further research is clearly needed.Fatty-acid soapsSoap products have been used formany years for lawn moss control, andanecdotal reports of control with productssuch as Dawn Ultra detergent,which is not labeled as a pesticide,prompted evaluation of soap productsfor use on putting greens. We screenedseveral products based on fatty acids,all of which were effective in killingCopper-induced Iron ChlorosisRelative residual moss control in plots treated the previous winter with Junction ( Copper Hydroxide + Mancozeb),No-Mas (fatty acid soap),Daconil fungicide,and an untreated check plot.GCM 105
Page 1: This work was partly funded by the

Controlling moss in putting greens - GCSAA

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