Spore production perpetuates the existence of moss. Great quantities of spores are produced during the life cycle of the plant.

Moss EradicationIn Putting Green TurfWith persistence it can be selectively removed.by KEITH A. HAPP

WITH ever-increasing demandsplaced on putting green turf,fueled primarily by the need

for speed, is it any wonder that sur-face management problems develop?Today's golf course superintendent isfaced with many turf managementdecisions, most of which are centeredon providing the best possible playingconditions. At times during this quest,plant health is compromised in orderto deliver the desired playing effect.While pursuing the ultimate ball rolland surface performance, bentgrassvigor can decline and the potential forweed development increases. Oneweed that can easily invade and fillavailable voids is moss. A small mosscolony can proliferate and turn into abigger problem that is more difficult toovercome. If conditions remain favor-able, moss can spread across a puttingsurface.

It has been reported that thousandsof species of moss exist. This is no

surprise, since moss has been aroundfor some 350 million years. Moss candevelop and thrive in many differentenvironments. Four mosses that ofteninhabit putting green turf are Byrumargentum, Byrum lisae, Ambly-stegium trichopodium, and Brachy-thecium spp. Each has its owncharacteristics. For example, Byrumargentum (silvery thread moss) isfound in open sites. Its silvery appear-ance allows it to be distinguished easilyfrom other mosses, and it is one of themost common contaminants of puttinggreen turf ..

Byrum lisae also is found in opensites but favors rocky or sandy soils.Byrum lisae is distinguishable fromother mosses by its green to yellow-green appearance, and its coloniesform tufts or clumps. Both species ofByrum mosses can tolerate a widerange of soil moisture conditions. Acommon misperception of Byrummoss is that it only competes well in

shady, damp sites where turf has littleor no chance of competing for space.Although it remains true that the bestdefense against weed encroachment isa dense stand of turf, Byrum moss canrapidly fill a void if the opportunity ispresented. Once established, and if theconditions remain favorable, Byrummoss will proliferate in full sunlight.

Amblystegium trichopodium, onthe other hand, is more difficult toidentify and thrives in saturated soils.As such, this moss may be a problemon heavy clay soils or areas of poordrainage. Brachythecium spp., whichalso thrives in wet soil conditions, isa common variety of moss referred toas "yard moss." Amblystegium andBrachythecium moss usually are foundin higher cut turf, but they can betracked easily into putting green sur-faces. These mosses can become estab-lished in the rough or perimeter areasof the course and spores can be spreadvia air or foot traffic.

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What is Moss?Moss is a photosythesizing terrestrial

plant. However, mosses are non-vascular plants and need to be incontact with water to avoid drying out.Many mosses absorb water over theirwhole surface, while others take inwater through their rhizoids in a man-ner similar to that of vascular plants.Mosses that can survive in a state ofdesiccation have fine, hairlike leavesthat can reflect the sun's heat. Cuticledevelopment is rare, and this results inmosses being adapted to shady, moistlocations. Mosses can, however, sur-vive long periods of desiccation, insome cases several years, and can with-stand high temperatures in a dormantstate. Laboratory studies have foundthat mosses can tolerate dehydrationlevels equal to 80% of original bio-mass. When mosses are rehydrated, animmediate respiratory burst is mani-fested' but recovery is slow. Addition-ally, research has provided evidencethat mosses can survive extendedperiods of dormancy by living symbi-otically with blue-green algae. Thisrelationship is important. Algae canbe viewed as a precursor to mossencroachment. Hence, addressing thefactors that encourage algae growth canpreventatively discourage moss coloni-zation. It is much easier to eradicatealgae than it is to selectively removemoss from putting green turf.

How Does Moss Reproduce?Although water is essential for their

sexual reproduction, mosses are mainlyland plants, and only a few species areadapted to aquatic environments. It ispossible for moss to reproduce bothsexually and asexually.

The sexual reproductive organs ofbryophytes (mosses) are very charac-teristic in form, but they have little'resemblance to those of floweringplants. Male and female organs maybe on separate plants or on the sameplant. In mosses the sex organs areusually interspersed with sterile hairsand are enclosed in leaves. This defensemechanism allows the moss to surviveprolonged states of desiccation.

Asexual reproduction can be facili-tated by water, wind, foot traffic, andeven by maintenance equipment. Forexample, a moss plant can be severedby a golf spike and then transported toanother area. When male and femalegamete cells come in contact, fertiliza-tion is possible and a zygote is formed.Additionally, moss bryophytes can

2 USGA GREEN SECTION RECORD

grow from small pieces of shoot or evenleaves. Once a zygote is formed it isprotected in specialized (gametophyte)tissue. The zygote then develops intothe sporophyte, which eventually re-leases spores. The reproductive cycleis complete when these spores developinto the gametophyte structures that areidentified as moss. Again, the primaryrequirements for completion of thiscycle are voids in the turf and sporesthat easily generate a new colony.

Mosses develop in response tophotosynthesis and also by nitrogenfixation in the absence of a light source.In the case of fixation, nitrate fertilizersapplied to stimulate growth of thedesired turf can be a catalyst for mossdevelopment. Thus, fertilization alonemay not adequately correct a mossproblem. To a certain degree, it couldexacerbate the undesirable condition.

How Can Moss Be Identified?Moss and slime/algae are different

types of lower plants. It is relevant toconsider them together because theiroccurrence and control measures over-lap. When moss first colonizes an areait produces a black, slimy mat acrossthe area before the green vegetativestructures form. The green structuresgrow into branch-like filaments calledprotonema. These are the threadlikestructures that bud out and developinto the gametophyte. The protonemaof mosses are extensive, resemblinggreen algae, and may persist formonths. In the life cycle of moss, it ispossible to wrongly diagnose and con-fuse this with algae. This is importantand reinforces the need to have a basicunderstanding of the life cycle of moss.Accurate diagnosis leads to accurateand precise treatment of the problemat hand.

Mosses can take many shapes andforms. Stems and leaves of moss arecomplex, most having conductingstrands, midribs, and a great diversity ofcell form. Shoots develop from tetra-hedral cells, and this results in three leafarrangements. Leaves may be groupedin pairs, threes, and even sets of five. Inthe majority of mosses, leaves are notarranged in regular rows. Except forthe midribs, leaves are one cell thick,with most or all of the cells containingchloroplasts. This particular featurecan be exploited when eradication isattempted. Disrupting photosynthesisof moss via selective desiccationmethods provides a competitive edgefor turf, provided the desiccating effectis maintained.

Mistakenly treating for algae mayinterrupt photosynthesis, but in thecase of mosses it has been shown thatthey will reproduce in the absence oflight. Furthermore, not even soil sterili-zation can guarantee that an area willbe free of dormant moss spores. Thedried-out vegetative state does notutilize water or nutrients but will allowreproduction when conditions areagain favorable. This further indicatesthe need to be persistent with controlmeasures. Control requires constantvigilance and an understanding ofwhen infestation takes place. Basically,if moss has colonized an area, an on-going eradication program is needed toassure that it will not continue to be aproblem.

The First Step inCorrecting the Problem

First, ask why moss has developedon the green. Take a step back andreview the management practices cur-rently in use.

• Are surface and subsurface drain-age systems sufficient to handlemoisture conditions?

• Are cutting heights too low?• Are fertilizer levels so low that

they are preventing turf growth?• Are the nutrients within the soil

in balance so as to provide an optimalenvironment for sustained turf growth?

• Has a topdressing change beenmade that could affect the manner inwhich water moves through the soilprofile?

• Finally, has irrigation frequencychanged and inadvertently become acausal factor of moss development?

Answering these questions couldprovide a solution to moss encroach-ment problems and insight as to whycolonization occurred.

To many, the solution may soundsimple: raise cutting heights and in-crease fertility to promote healthy turf.But will contemporary golfers acceptslower putting green speeds? From myexperience, the answer is "no." Aholistic approach, combining culturaland chemical means, may provide amore acceptable answer.

Cultural StrategiesA strong cultural management pro-

gram can help to reduce the potentialfor moss encroachment. For example,aeration is the cornerstone of manymaintenance programs. Aeration inany form helps to improve infiltrationrates, which in turn helps to dry the soilsurface and provides a competitive

If conditions are favorable, moss can spread across a putting green and be carriedfrom surface to surface. A small moss colony can proliferate and turn into a biggerproblem over time.

edge to the desired turf. Physicallyremoving thatch may also provideassistance in defeating moss popula-tions. The fact is, small-tine shallowaerification has gained wider accept-ance by both turf managers and golf-ers. Small-tine aeration, such as withquadratines, provides agronomic bene-fit without creating a great deal ofsurface disruption, and it is an excel-lent proactive management strategywhether moss is present or not.

In combination with small-tineaeration, light and frequent topdressingapplications are a common practice.On heavy soil greens, the main benefitrealized from this maintenance strategyis increased water infiltration. Basically,a green with better surface character-istics is being established on top of anative soil material. On new USGAgreens or other high-sand-contentgreens, the benefit realized is goodthatch management. To maintain abalance of water and air in the profile,and particularly near the soil surface,the thatch must be constantly diluted.As soil porosity increases, so does thelikelihood that moss encroachmentcan be brought under control. Allow-ing the moisture to move freely into thesoil rather than remaining on the sur-face reduces the potential for mossdevelopment. Also, as topdressing isapplied, moss spores that may bepresent near the surface will be buried.

Examining changes in topdressingmaterials may offer clues as to whymoss encroachment has occurred.

Changes in the particle size of thetopdressing sand or the use of adifferent organic matter in the mixcould produce long-term problems.Periodic sampling and testing by aqualified physical testing laboratorycan add both a check and a great dealof peace of mind. Problems can beavoided when a strong quality controlprogram is in place.

A balance between cutting heightsand fertility levels must be established.The overall goal of any maintenanceplan is to provide healthy, vigorous turf.If this maintenance plan is compro-mised for the sake of ultra-fast greenspeeds, then weed invasion should beexpected. It has been observed thatmoss growing on a putting surface willnot encroach into the surroundingcollar area. Quite simply, turf cut at agreater height resists invasion. Raisingthe mowing height as little as y:'2" hasshown positive effects in reducingmoss populations. Even raising theheight of cut from 'l8" to 0/64" provides13% more leaf blade. Greater leafblade surface area enables the turf tobecome more vigorous by increasingphotosynthesis. There are many othertools available to manage puttinggreen speeds. Growth regulators, forexample, can be applied in combi-nation with other grooming tactics toenhance surface performance.

FertilityA Scottish greenkeeper once said,

"Moss is a sign of poverty in the soiL"

This is an amazingly accurate statementthat has been verified by university re-search. There are some distinct nutrientdeficiencies and relationships thatfavor moss encroachment. Researchindicates that calcium-rich soil mayexacerbate Byrum moss development.Areas of moss colonization tend tohave higher calcium-to-magnesiumratios and a higher percentage of siltand clay in the surface. This soil textureaccounts for the increased waterretention due to reduced percolation.Examining the nutrient status and thephysical properties of the soil thereforemay provide a great deal of informa-tion not only to defeat moss, but alsoto promote the healthiest stand of turfpossible. If calcium levels are high,MgS04 (Epsom salt) treatments may bewarranted. Magnesium is a componentof chlorophyll production, and its addi-tion into the soil could enhance turfvigor.

There is a correlation between mosspopulations and potassium (K) levelsin the soil. Moss pressure seems toincrease as K levels decrease. As such,monitoring K levels in the soil isimportant. If deficiencies exist, correc-tive applications can be made in thespring or fall. Sulfate-of-potash treat-ments provide a safe means to achieveadequate K levels.

Various fertilizer treatments havebeen applied to selectively retard mossgrowth while the desired turf is pro-moted. Ammonium sulfate, for example,has performed well in many studies.This fertilizer is thought to produce aselective desiccating effect on mosswhen applications are made frequentlyand at low dosage rates. Treating with'll2 to 'l8 lb. of N/1000 sq. ft. per weekcan produce positive results. This treat-ment regime also provides an acidifyingeffect that can produce desirable sideeffects. Patch diseases may be lesslikely to develop when the pH of thesoil is managed in this manner.

Ferrous sufate applications have alsobeen closely examined for their effecton moss. In fact, in 1933 calcined ironsulfate was a common treatment formoss problems. Iron treatments, in theform of iron sulfate, can be applied ata rate of 2 ozs./1000 sq. ft. every otherweek during the summer or at higherrates during the fall and winter. Up to3 Ibs. of iron sulfate/1000 sq. ft. hasbeen applied to moss-infested puttinggreens, and this treatment strategy re-mains common in the British Isles. Theeffect of the treatment is dramatic. Theturf takes on a dark green or even black

SEPTEMBER/OCTOBER 1998 3

appearance due to the chlorophyllsurge. Moss colonies may experience aselective desiccating effect and the turfrecovers. Positive signs of the desic-cating effect on moss are exhibited byan orange-brown or golden-browncoloration. This is the initial sign ofmoss decline, but it is by no means anindication that treatment strategiesshould stop. As previously stated,persistence is the key.

Hydrated lime and copper sulfatehave been suggested as treatments formoss contamination problems. How-ever, the effect on the pH of the soil isof greater concern regarding the use oflime, and copper sulfate applicationsdo not offer a wide margin for error. Inmany instances, the results of thetreatment may be worse than theoriginal problem.

Potassium of fatty acid (DeMoss) isa labeled product for moss control. Thetreatment procedure is similar to that ofammonium sulfate applications. Thematerial must be applied frequentlyover an extended period of time toachieve the desired effect. Applying 2to 3 ozs. of material/1000 sq. ft. everyweek can produce a significant reduc-tion in moss populations, and theconsistency with which the material isapplied is an important ingredient forsuccess.Chemical Treatments

Timing of chemical applicationsappears to be crucial to their success.Studies have tested control measuresduring maximum sporophyte develop-ment in the spring and found thatselective eradication can be achieved.

Maneb- or Zineb-based fungicidesapplied to moss during its early stagesare phytotoxic to young/immaturemoss plants and algae. Also, there areindications that Maneb treatment mayinhibit N-fixation with respect to thesymbiotic relationship of moss andalgae. Treatments render populationsunable to produce carbohydrate re-serves and thus unable to compete forspace. Maneb is a broad-spectrumfungicide, but it produces herbicidalaction favorable to moss control.Case Studies in Moss Control:Case Study #1

Spot treatment procedures have alsoprovided satisfactory control of moss.DeMoss (Mycogen Corporation) hasbeen applied in combination withwetting agents and a surfactant. ToddVoss, of the Double Eagle Golf Club,experimented with a combination ofmaterials, which included DeMoss, on

4 USGA GREEN SECTION RECORD

Moss also responds to fertilization.A blackening of the moss often does notsufficiently desiccate the moss colony.Fertilization must be persistentlyemployed to achieve the desired result.

his sod nursery. The initial goal wasto find a mixture that would applyselective pressure to moss withoutharming the desired stand of bent-grass. Once satisfactory results wereachieved, the spray combination (1 oz.DeMoss, 1 oz. Lesco Wet, 1 oz.spreader sticker in 32 ozs. of water)was applied to moss populations onthe course. Treatments were performedin the afternoon during the summerand continued throughout the fall. Thetreatments were performed with ahand-held squirt bottle calibrated todeliver repeatable applications.

Three to four squirts from the spraybottle adequately soaked the mosscolonies. Within 24 to 48 hours, mosspopulations exhibited the orange toorange-brown color, signifying that apositive desiccating effect had oc-curred. Repeat treatments were per-formed depending on the density ofthe moss colonies and the spore popu-lations in the soil. Minor phytotoxiceffects were exhibited on the turf. But,via fertilization, the turf grew out ofthe herbicidal effect caused by themoss control mixture.

In combination with this eradicationtechnique, spiking and oversee dingwere performed. As bentgrass popu-lations increased, interspecific compe-tition increased, and moss colonizationwas minimized.

Case Study #2Another treatment strategy that has

shown promising results is the use ofDawn dishwashing detergent. Thedetergent provides an excellent selec-

tive desiccating effect on moss popu-lations and due to the ingredients of theproduct may also provide cryptocidaleffects on the moss spore populationsin the soil. Although Dawn has beentested at universities (Danneberger1998, Landschoot 1998) and used suc-cessfully on golf courses, it is notcurrently labeled for use for mosscontrol on turf and thus is not legalfor this use at the present time.

John Keeler, of Hershey's Mill GolfClub, experimented with a number ofcontrol techniques on a designated testsite. Applications of iron sulfate weretested at various rates, in addition toDawn treatments. A check plot wasalso established to better evaluatetreatment performance. Dawn treat-ments ranged from 2 ozs. to 8 ozs. ofmaterial/1000 sq. ft. The product wasdelivered to the moss colonies with aminimum of 1 gal. of water/lOa a sq. ft.

An immediate response was ob-served following the application ofDawn. First, a water-soaked appear-ance was observed in the treated areas.Within 48 hours the moss coloniesexhibited the classic orange or orange-brown discoloration while the sur-rounding turf showed no signs ofphytotoxicity. After testing was formed,the material was applied to moss-infested sites throughout the course,and within a four- to six-week periodacceptable moss control was achieved.

Although the treatment strategy cen-tered on Dawn applications, a holisticprogram was put in place. Topdressingwas applied periodically and nitrogentreatments were made on a routine in-terval. Putting green speeds were main-tained in the sufficient range with theuse of walk-behind mowers and infre-quent rolling. Irrigation was applied tosupport turf growth, but not to thepoint of overly saturating the soil pro-file. Basically, every effort was put forthto strengthen the basic agronomic pro-grams in order to allow moss controltechniques to be as effective and long-lasting as possible. Surface perfor-mance was improved, and this led toheightened golfer enjoyment.

Case Study #3John Klosiewicz, of the Vic Meade

Hunt Club, utilized a combination ofmethods to overcome a serious mossinfestation problem. The problem wasso bad that reconstruction was thoughtto be the only corrective procedureavailable.

The road to recovery began withheight-of-cut adjustments. The mowers

were raised to ~2". Fertility levels werealso increased, with ammonium sulfateand urea being the main sources ofnitrogen. Chemical analysis of the soilprovided evidence that high solublesalt problems existed, and this wasaddressed by treating with magnesiumsulfate and gypsum.

The chemical analysis led to ques-tions about how the salt problemsdeveloped. To find answers, the top-dressing material was submitted forboth chemical and physical analysis.The results indicated that the top-dressing was a contributing factor dueto its moisture retention capacity. Aprogram of aggressive aeration wasimplemented to help remove thatchand soil. Following aeration, a carefullyselected straight sand topdressing wasapplied to fill newly created columnsto the surface. This was supplementedby weekly treatments of between 50and 100 lbs. of material/lOOO sq. ft.throughout the season. Soil porosityimproved dramatically and this allowedthe surfaces to be maintained in a muchdrier state.

After the physical properties of thesoil were addressed, the next step wasto selectively attack the moss colonieson the greens. During the months ofDecember and February, iron sulfatewas applied at a minimum rate of 2lbs. of material/lOOO sq. ft. This beganthe selective desiccation process. Asthe spring weather arrived and soiltemperatures increased, urea andammonium sulfate products were ro-tated into the treatment regime. Eachwas applied at a rate of Y8lb. N/lOOOsq. ft. per week. The bentgrass re-sponded to the increased N level andthe moss became much less prevalent.Still, another method of eradicationwas needed.

In combination with fertility adjust-ments, DeMoss was applied everyother week at a rate of 1 to 2 ozs. ofmaterial/lOOO sq. ft. Only severelyinfested greens were treated in thismanner, while spot treatments wereperformed on greens that exhibitedonly minor infestation. Bentgrass seedwas introduced regularly during theentire eradication process. This inte-grated approach to moss control paidoff; non-target damage was minimizedand bentgrass populations increaseddramatically.

Using a combination of techniques,the moss problems were brought undercontrol in seven months. During thistime, the playability of the surfaces didnot suffer. Multiple mowings, light and

frequent topdressing, growth regulationtreatments, and rolling were used tomaintain acceptable conditions.Conclusion

The control of moss should beapproached as a long-term project. Ittakes time for moss to develop intocolonies that both visually and physi-cally affect the playability of greens.Therefore, it is reasonable to expect thatit will take time, often a long time, toreverse the undesirable condition.

The immature stage of moss coloni-zation (the protonema) is highly sus-ceptible to desiccation. If properlydiagnosed during this early stage ofdevelopment, site-specific treatmentperformed in a carefully thought -outmanner could provide excellent results.Cultural practices such as spiking,aerification, topdressing, oversee ding,and proper fertilization should accom-pany the use of a selective eradicationproduct.

All aspects of management should beconsidered when battling moss. Is thesunlight sufficient to allow the turf tocompete and fend off invasions? Is theair movement around the problem areaadequate to permit soils to be purged ofexcessive moisture? Drainage shouldbe corrected or installed where it isinadequate or nonexistent. Deep-tineaerification can provide relief whencompacted soil conditions exist.Thatch management will enable goodrooting and thus increase the vigor ofthe turf. Any preventative measureshould be done with the overall goalbeing to promote healthy, vigorousturf. After all is said and done, healthyturf is the only way to cure and preventmoss invasion.

KEITH A. HAPP is an agronomist inthe Mid-Atlantic Region, visiting coursesin the states of Delaware, Pennsylvania,Maryland, Virginia, and West Virginia.Keith joined the Mid-Atlantic staff in 1993.

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