Of Moss and MenResearch trials from across the u.s. have identified control options forthis invasive weed of putting green turf Field observations indicatemanagement is an important component of successful eradication.

BY MATT NELSON

MOSsinvasion of putting greenturf has become an increasingproblem at golf courses across

the United States over the past tenyears. Moss encroachment into puttinggreens has progressed from a regionalconcern a few decades ago to a morewidespread problem on creeping bent-grass greens with sand rootzones dur-ing the late 1990s, to an even widerproblem today on greens with mixedstands of creeping bentgrass and annualbluegrass growing in a variety of root-zone compositions. As a result, researchconducted at various sites across thecountry has identified control methodsand probable causes of moss invasion.

WHERE DID IT COME FROM?Silvery thread moss (Bryum argenteum),the moss species that invades puttinggreen turf, is a primitive plant adaptedto a variety of climates around theworld.1.3.6.11Moss is a non-vascular plantthat must be in contact with free waterto establish. Moss also can toleratenearly 80% dehydration, however,which makes it extremely well adaptedto and competitive in putting greens.It reproduces sexually via spores thatcan be disseminated over great distancesby wind. Moss also can reproduceasexually from displaced fragments,which is a likely means of spreadingacross golf course putting greens.Water, wind, maintenance equipment,or foot traffic can effectively spreadmoss.

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Research agronomists speculate thatincreased moss encroachment problemscan be correlated to discontinued useof mercury fungicides and perhaps achange in pesticide formulations.3.9.11.12.13A more likely explanation is continuedreductions in mowing height andinsufficient nitrogen fertilization ofputting green turf with the intent ofpromoting faster green speed.3.6.7.8.9.12.13Lower mowing heights and reducedfertility compromise the competitiveability of turf and increase opportunityfor weed invasion. This claim is sup-ported by the progression of moss inva-sion from select regions of the countryto more widespread observation oncreeping bentgrass turf growing insand rootzones, to greens of all mixesof annual bluegrass and creeping bent-grass in a wide variety of soil media.Sand retains less nutrients and waterthan soil, and bentgrass typically hasless density (shoots per unit area) thanperennial biotypes of Poa annua atmowing heights below ~ inch. Mossinvasion problems in collars, tees, andfairways are undocumented.

As a result of more widespread mossproblems, golf course superintendentsand researchers have experimentedwith a plethora of potential controlagents, including liquid soaps, fattyacids, baking soda, mouthwash, fabricsoftener, various metals, fungicides,herbicides, peroxides, various combi-nations of these materials, and whoknows what else. Fortunately, con-

trolled research efforts have yieldedsome positive results.

CALL IT ... HEAVY METAL!In the past, heavy metal fungicideswere a one-way ticket to moss-freegreens. For good reasons, these productsare no longer available for use in theturf industry. Weber and McAvoydemonstrated effective moss controlwith silver nitrate by electromotivedestruction of chlorophyll, wherebythe magnesium ion at the core of thechlorophyll molecule is oxidized bythe metal ionY A silver nitrate pesti-cide has not been registered for useon golf turf

Iron sulfate has long been recog-nized as a viable control tool, althoughrepeated application at high rates isnecessary to provide good control. 3.7.12High rates of iron sulfate applied re-peatedly with very high water volumehave demonstrated effective eradicationof moss at several golf courses in thewestern U.S., although some research-ers have questioned the long-termconsequences of such a program.2

Copper hydroxide fungicideshave been shown to provide effectivemoss suppression through researchconducted at Oregon State University,Cornell University, and Penn StateUniversity.3.7.9 Four to six applicationsof copper hydroxide fungicides atweekly intervals in the fall have pro-vided the best results. Water pH iscritical to control and additives are

necessary to be sure that water in thespray tank is adjusted to a pH of 5-6.5prior to adding the copper hydroxideproduct. Repeated copper applicationscan inhibit iron metabolism in theplant and result in toxicity problems inthe soil. Observation in the RockyMountain region of the U.S. indicatescopper hydroxide can effectively con-trol moss, but this approach has notbeen widely practiced.

ANOTHER "CIDE"OF CONTROLResearchers have discovered thatanother fungicide (chlorothalonil) andone herbicide (carfentrazone) can pro-vide selective control of moss in putt-ing green tur£tO,12,13Results indicatethat sequential applications of chloro-thalonil can provide good control ofmoss without turfgrass phytotoxicitywhen daytime temperatures are above80 degrees F.12Use of this productwhen temperatures are cool exhibitslimited efficacy on moss, so using thisproduct in a disease management pro-gram will provide moss suppression.Label limitations on annual chloro-thalonil use on greens must be con-sidered when using this product formoss control.

Carfentrazone (Quicksilver, FMCCorp., Philadelphia, Pa.) has recentlygained registration for silvery threadmoss control on putting greens, andresearch trials have shown good toexcellent control.tO,13 Carfentrazoneappears to provide good control ofmoss over a broad temperature range.Field observation in the western U.S.has shown excellent moss controlresults when applications are madebetween daytime temperatures of 55and 85 degrees F. Two or three appli-cations 7 to 14 days apart at the labelrate in 100 gallons of water per acrewith a non-ionic surfactant at a rate of0.25% volume/volume have demon-strated the best results. Since moss lacksroots and vascular tissue and has anextremely high biomass surface relativeto volume, spray volume and surfactant

Moss invasion has been linked to low mowing, and invasion is often first noticed on ridges or crowns inputting greens where scalping is more likely.

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Copper products, desiccation control agents, and carfentrazone typically cause moss to turn a bronzeor brownish color, indicating efficacy. Repeated applications are usually required with any product toprovide acceptable moss eradication.

Iron tends to blacken moss when used as a selective control. In this case spot applications fail tocontrol smaller moss plants evident in the turf canopy, and they seldom provide acceptable control.

Sodium carbonate peroxyhydrate(Terracyte, Biosafe Systems, Glaston-bury, Conn.) is currently marketed forselective control of silvery thread mosson golf courses, and field observationshave demonstrated poor to excellentmoss control. This product uses grounddolomitic limestone as a carrier andcan be difficult to apply accurately.Terracyte may cause some turf injuryto annual bluegrass and creeping bent-grass during high temperatures and lor

. humidity, especially if consecutive daytreatments are used? At PSU, 4 to 5applications of Terracyte at 8 lb. per1,000 sq. ft. every two weeks providedgood control, although it did not eradi-cate moss. As with copper products,Cornell University researchers havefound better control with this productin fall vs. spring.9 They speculate thatmoss is either more susceptible to con-trol or has less recuperative potential inthe fall. Best results with this productin field observations from the westernU.S. occur when turfis lightly irrigatedimmediately before and after applica-tion at an 8 lb. per 1,000 sq. ft. ratewith a drop spreader. Spot applicationsdo not typically provide acceptablemoss control.

demonstrate effective controP Spotapplications of Dawn Ultra at a 4 oz. Igal. of water dilution rate seem toprovide better moss desiccation thanbroadcast applications in field observa-tions. Again, this product is not aregistered pesticide.

use are important for maximumcoverage, absorption of product, andcontrol. To date, carfentrazone hasprovided the best selective control ofmoss in putting greens across thewestern U. S.

OTHER OPTIONSAs mentioned previously, many differ-ent materials have been evaluated formoss control in the field. Researchersin Illinois have shown that baking soda,when spot applied in a solution of 6 oz.baking sodal gallon of water, is capableof providing season-long control,although significant turf injury isprobable with baking soda use.1O Also,broad application of this product maybe difficult, and spot treatment withany product rarely provides acceptablemoss control. Visible moss coloniesoften indicate a more widespread mossinvasion when close analysis of theturf grass canopy is conducted. Bakingsoda is not registered as a pesticide.

Dawn Ultra dishwashing liquidhas provided variable moss suppressionin the field, although researchers atPenn State University were unable to

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Thatch and/or layering in the upper soil profile can predispose turf to moss invasion. Notice the lack ofmoss in the perimeter of this green where mowing imparts more wear injury and limits productivityand thatch production.

THE CULTURE OFMOSS CONTROLWhile research continues to identifyselective controls of silvery thread mossin putting green turf, adjustments incultural management programs are thereal key to achieving long-term mosssuppression. Without question, lowmowing and insufficient fertilizationare the primary causes of moss infesta-tion. Ridges, crowns, and other areasprone to scalping injury are typicallythose that moss first invades. Increasingthe height of cut and fertility whenapplying products to selectively controlmoss will improve success. Utilizerolling or double mowing to achievethe desired green speed in lieu ofmowing too low.5 Field observationindicates moss infestation problems areabsent or much less severe when nitro-gen fertilizer is applied at 0.4-0.5 lbs.N per 1,000 sq. ft. per month of activegrowth.

Since moss must be in contact withfree water to establish, even micro-scopic layers in the upper soil profilemay be sufficient to effectively perchwater and favor moss. Controllingorganic matter in the upper soil profilewith aeration and topdressing isintegral to good moss control. Otherfactors that affect turf grass vigor,including the growing environment,irrigation practices, traffic manage-ment, and drainage, should be evalu-ated if moss infestation is noticed orhas become a serious problem. Minoramounts of moss can quickly become amajor problem if left unchecked, soreview the research and implement acomplete control strategy early.Ultimately, the best advice whenbattling moss is to evaluate all factorsand grow grass, not moss.

LITERATURECITED1. Burnell, K. D., F. H. Yelverton,). C. Neal,T. W. Gannon, and). S. McElroy. 2004. Con-trol of silvery-thread moss (Byrum argenteumHedw.) in creeping bentgrass (Agrostis palustrisHuds.) putting greens. Weed Technology. July-Sept. 18(3):560-565.

2. Cook, T. 2005. Ironing out your fertilizerprogram. USGA Green Section Record. MarchiApril. 43(2):19-21.

3. Cook, T., B. McDonald, and K. Merrifield.2002. Controlling moss in putting greens. GolfCourse Management. Sept. 70(9):103-106.4. Dudones, D., and F. Rossi. 2001. Silverythread moss research at Cornell University.Cornell University Tuifgrass Times. Summer.12(2):6-9.5. Gilhuly, L. 2006. Green speed: Trick ortreat? USGA Green Section Record. July IAugust.44(4):17-19.

6. Happ, K. A. 1998. Moss eradication inputting green turf USGA Green Section Record.Sept./Oct.36(5):1-5.7. Landschoot, P.,). Cook, and B. Park. 2004.Moss control- new products and strategies.USGA Green Section Record. July IAugust.42(4):7-9.

8. Nelson, M., and L. Gilhuly. 2005. Where isgreen speed taking the game? USGA GreenSection Record. May/June. 43(3):8-10.9. Rossi, F. 2002. Cornell researchers tacklemoss control. Cornell University Tuifgrass Times.Spring. 13(1):10-11.

10. Settle, D. M., R. T. Kane, and G. L.Miller. 2006. Evaluation of newer products forselective control of moss on creeping bentgrassgreens. USGA Tuifgrass and EnvironmentalResearch Summary. p. 64.

11. Weber, A. P., and T. O. McAvoy. 2003.Moss infestations in putting greens. USGAGreen Section Record. July IAugust.41(4):32-36.

12. Yelverton, F. H. 2005. Managing silverythread moss in creeping bentgrass greens.Golf Course Management. March.73(3):103-107.

13. Yelverton, F. H. 2005. Moss on bentgrassgreens - why do we have it and how do youget rid of it? Presented at USGA regional confer-ence. Pinehurst, N.C.

MATT NELSON has observed moss acrossawide range of climates, management pro-grams, and construction types as senioragronomist in the Green Section'sNorthwest Region.

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