APPLICATOR'S LOG,..Disease Management in Sports Turf

By Dr. Gail L. Schumann

Diseases of turf grass may seemto appear suddenly and with-out warning, but the truth isthat there is usually a specific reasonwhy a disease has occurred. Whenthese problems arise, it is worth a littlediagnostic detective work to help pre-vent future outbreaks and to speedrecovery from the current epidemic.

Diagnosis of common turf diseasesmay be very easy or exceedingly frus-trating. Some common diseases showsymptoms that are readily recognizedeven without a microscope; others canbe diagnosed accurately only in a labo-ratory. When a turfgrass disease doesnot easily match up with the picturesin a book, other possible causes of turfproblems need to be considered.Mowing injury, insect problems, or mis-application of fertilizers and pesticidescan all cause symptoms that might besimilar to disease symptoms.

Fungi cause most turf diseases.These disease-causing organisms areactually parasites that use turfgrass asa source of nutrients. They are com-prised of growing filaments (mycelium)and reproduce by forming spores.Spores are survival structures for afungus. They also serve as packets offungus that can be dispersed acrossgrassy areas on feet and mowers, espe-cially in wet conditions. Once turf hasbeen established for a few years, it islikely that most of the fungi that causethe common diseases are present andwaiting for an opportunity to infect thegrass plants.

The Disease TriangleDisease occurs only when three fac-

tors are present: a pathogen, a suscep-tible plant and an environment favor-able to the disease. The fungi thatcause common turf diseases are gener-ally microscopic, so your field observa-tions will be limited. When the grass iswet, however, it is common to see themycelium and/or the spores of the fun-gus that is causing a disease. While notall fungi, particularly root-infecting

fungi, will be visible without a micro-scope, the observation of an active fun-gus is invaluable in disease diagnosis.

Colorful DiseasesSeveral common turf diseases are

easily recognized by the colored myceli-um and spores visible on wet grass. Incool, wet weather, the fungus responsi-ble for red thread disease produces tinyred threads on the tips of the leafblades. Tiny cotton candy-like puffs ofspores are produced by the same fun-gus. These spores are sometimes visi-ble even when the red threads are notobvious. Red thread develops bestwhen turfis growing poorly due to com-paction, low fertility and other stresses.

Rust is another common diseasethat is easily identified by its color.Often you can see it on white athleticshoes, which may become covered withthe orange, powdery spores duringsevere outbreaks. Like red thread, rustis most prevalent in grass that's grow-ing slowly due to compaction, low fer-tility or dry soil. The spores take 10 to14 days to form following infection.This means that infection on well-maintained grass is usually mowed offbefore the spores can form. Rust ismost common in late summer and fallin many northern areas. It rarely killsplants, but can weaken them and makethem unsightly.

Several common turfgrasspathogens produce white mycelium onwet grass, especially in the early morn-ing. The mycelium is very similar tospider webs, and may even be confusedwith cottonwood seeds in spring andearly summer (actual cottonwood seedscan usually be felt when rubbedbetween the fingers). The two mostcommon diseases associated with whitemycelium are dollar spot and Pythiumblight. Dollar spot typically occurs inwarm, wet weather on low fertility turf.Infected leaf blades are often straw col-ored below the mycelium. Pythiumblight generally occurs in hot, wetweather on high fertility turf. Infectedleaf blades look greasy.

22 sports TURF• http://www.sportsturfonline.com

From a distance, the white myceliumof the dollar spot fungus looks simi-lar to cottonwood seeds. Photos by:Gail Schumann.

The distinctive orange color of turf-grass with rust disease is common inlate summer and fall.

Looking for CirclesIt is not a coincidence that most tur-

fgrass-disease names include the words"spot" or "patch." Fungi generally beginto grow outward from a central point toform circular spots or patches of dis-eased turfgrass plants. You are mostlikely to observe the circular nature ofdiseases in the early stages, before thecircles coalesce into a large, blightedarea. Circles from diseased spots andpatches are also most obvious at thelow mowing heights of golf puttinggreens, and may not be as distinct atthe higher mowing heights of sportsturf. Some important diseases, such asleaf spot, develop in irregular areasrather than circular patches.

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Factors That Favor Fungi

Most leaf-infecting fungi requirewater droplets on the grass blades, sotheir spores, like seeds, can absorbwater, germinate and produce newmycelium. Extended periods of rain orirrigation favor infection. Irrigation inthe late afternoon or early evening mayfavor disease by increasing the timeturf remains wet each night. Excessive

Red thread occurs in cool, wet weath-er and is common where soil is com-pacted or turf is stressed. The turfoften has a pink or reddish look.

Environment DeterminesDisease

Many fungi have a temperaturepreference, so we expect certain dis-eases whenever an extended period ofcool, warm or hot weather occurs, espe-cially when it is accompanied by excessmoisture. In cool weather, expect leafspot and red thread. As weather getswarmer, dollar spot and necrotic ringspot may develop. In hot weather,brown patch and Pythium blight aremore likely.

Turfgrass is more susceptible to cer-tain diseases when it is stressed.Examples of stress factors include soilcompaction, drought, poor drainage,mower scalping, dull mower blades,low or unbalanced fertility, and soil pHthat is too high or too low. Diseases thatare more common in stressed turfinclude dollar spot, necrotic ring spot,red thread and rust.

Necrotic ring spot can be verydestructive. It is caused by a fungusthat infects the roots of the plant, somost of the damage is done by the timethe above-ground symptoms are

observed. These symptoms includerings (frog-eyes) or patches of deadgrass about 8 to 12 inches in diameter.Symptoms are common in early sum-mer and fall. Damaged areas may beoverseeded with perennial ryegrass,which is not susceptible to the disease,or with Kentucky bluegrass and finefescue cultivars with tolerance to thedisease.

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January 1998 23

nitrogen applications may produce suc-culent leaf growth that is more suscep-tible to infection by fungi. Abundantmoisture and excess nitrogen favorinfections by the fungi that causebrown patch, leaf spot/melting out,powdery mildew and Pythium blight.

Leaf spot fungi are common inspring and fall in cool, wet weather. Ifonly a few leaf spots are present on aleaf blade, they may be mowed away asthe grass grows. Early spring nitrogenapplications can cause a burst of succu- .

lent leaf growth. If this is followed byprolonged wet weather, many leaf spotinfections may occur, leading to blight-ing of the entire blade and a thinning ofthe grass called "melting out."Overseeding damaged areas withgenetically resistant cultivars is usual-ly more effective than fungicide appli-cations for the long-term control of thisdisease.

Special CircumstancesSnow molds and damping-off are

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two disease situations that require aslightly different approach. The fungithat cause snow mold grow best on turfblades beneath the snow. Thus, snowmold is most severe when turf is stillgreen and succulent at the time of last-ing snowfall. Typhula blight (gray snowmold) can appear very severe after thesnow melts, but it does not generallykill the plants. The turf will usuallyrecover with the return of warm weather.

Fusarium patch (pink snow mold)can occur even without snow cover, andis commonly seen in prolonged wetweather at cool temperatures.Fusarium patch results in small red-dish, greasy spots. Mowing and foottraffic can track the fungus across turf,causing widespread blighting.Fusarium patch is more severe wheresoil pH is high and can be exacerbatedby lime applications in the fall. To avoidboth snow molds, do not delay turf dor-mancy by late fertilizer applications.When possible, minimize the time turfis covered with snow with snow fences,and avoid piling plowed snow on turf.

Damping-off is the term used todescribe the loss of seedling turf andseed rot. Many fungi can cause damp-ing-off, but Pythium is the most com-mon cause in wet weather or whereturf is overwatered. Overseeding ofsports turf puts seedlings at risk ifenvironmental conditions are not opti-mal for seed germination. Fungicidesare not usually helpful once very youngplants have been infected.

Are Fungicides the Answer?Fungicides are a useful way to con-

trol diseases when mother nature isproviding too much rain. Routine fungi-cide applications should not be neces-sary. Many turf diseases develop duringunusual weather. conditions that areonly temporary. Once the weather pat-tern changes, the disease may no longerpose a serious threat to the health of theturf. Fungicides will not bring dead tur-fgrass back to life. Overseeding dam-aged areas and correcting faulty irriga-tion or mowing practices may be moreeffective solutions. Finally, not all turfproblems are diseases. If a clear diagno-sis is not possible, a fungicide is proba-bly not justified, because it is not possi-ble to choose the right product or applyit at the correct time. Sound culturalpractices are the best approach tohealthy turfgrass. 0

Gail L. Schumann, Ph.D., is anassociate professor of plant pathology atUniversity of Massachusetts, Amherst,MA 01003.

Correction: In previous issues, sports TURF print-ed incorrect membership prices on the STMA member-

ship application form. Prices are correct as they appear

on page seven of this issue. We apologize for any

inconvenience this may have caused.

Rolling Stones HelpKickoff Nor-Cal

Wien the Northern CaliforniaChapter of the Sports TurfManagers Associationheld its firstever meeting at the Alameda CountyComplex, its 170 members were greetedby a massive six story stage built for theRolling Stones' "Bridges to Babylon" tour.Throughout the day, stage hands andconstruction crews assembled the intricatesteel-rigging using cranes, forklifts, tractorsand trucks. Itwas easy to see the challengesthe extravagant show presented the turfmanager, who was expected to grow ahigh-quality professional sports fieldunder those conditions.

Attendees of the grand opening hada chance to observe activities on thefield from the country-dub-like settingof the Coliseum's West Side Club, whereNor-Cal STMA President Sal Genitoopened the day's activities. He introduced

STMA inActionand thanked thechapter's 17 com-mercial sponsors,who made a strongcommitment to thegroup by providingseed money toestablish the chap-ter. Without thesecommercial sup-porters' willing-ness to getinvolved, the chap-ter would not exist.

Next came pre-sentations by BobMilano, sports As Nor-Cars meeting progressed, so did construction ofturf manager, the six-story-high stage for the Rolling Stones tour.University ofCalifornia, Berkeley, on sand-basedfield technology; Steve Trusty, STMAexecutive director, on the national asso-ciation and its services; and SteveWightman, turf manager, Qualcomm

Stadium, on sports turf management"then and now."

Wightman focused on how our pro-fession has changed over the last 20years, and how professional associa-

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tions are critical in such a specialized industry. He illustrat-ed his point by reading a job opening from a past newspaperfor a stadium turf manager, and it required "a high schooleducation, reliability, and some experience with turf mainte-nance." He then read a job opening for a stadium managertoday: "must have a four-year degree in turf management orrelated field, must be proficient in computer irrigation man-agement and personnel management; and must work cooper-atively with decision-makers such as stadium manager, teampresidents, owners, etc." Clearly, the industry and expecta-tions have grown.

The day concluded with walking tours of the Coliseum andthe New Arena in Oakland, the rebuilt home of the GoldenState Warriors. Oakland .Ns head grounds-keeper ClayWood answered questions and described how he planned toresod the entire football playing surface for the remainingRaiders home games after the four - yes, four - RollingStones concerts. (He did a superb job, in a very short windowthat was complicated by rain almost every day.)

The Nor-Cal Chapter is off to an unprecedented start, andalready it's planning for a community service project and afield day in 1998.

STMA Chapter NewsMidwest Chapter: The Midwest Chapter held its annu-

al meeting December 3 at the Pheasant Run Resort & ExpoCenter in St. Charles, Ill., in conjunction with the Sports TurfTrack of the North Central Turfgrass Exposition. Elected for1998 are the following officers: president, Scott Pippen,Village of Lincolnshire; vice president, Jim Lewandowski,Hinsdale Central High School; past president, Marc VanLanduyt, Van's Enterprises; treasurer, Donald Michaels,Conserv FS; and secretary, Tom Breier, National Seed Co.

For information, call The Chapter Hotline: (847) 439-4727.Iowa Chapter: The Iowa Sports Turf Managers

Association will again participate in the Iowa 'IurfgrassConference, held January 26-28 at Des Moines ConventionCenter.

The Monday, January 26, Sports Turf Workshop morning ses-sions include: 'Winning Fields = Winning Teams," by DuaneBanks; "Setting Up for Practice," Mike McDonald; ''PatternMowing," Luke Yoder; and Round Table Discussions: "Dealingwith Soccer/ Football on the Same Field and Heavy Use Fields,"led by Gary Peterson; "Football/Soccer Painting (Rules,Techniques and Logos)," Mike Andresen; "Fertility/SoilSampling," Ron Crooker; "Baseball/Softball Mound &Homeplate Maintenance," Luke Yoder; "Picking an Infield Mix,"Jesse Cuevas; "Football/Soccer Goalmouth Maintenance,"KevinVos.

The afternoon session offers a combined golfcourse/sports turfsession, "Selecting Sands and Soil Modification," presented byDr. Jim Crum.

The sports turf session on Thesday afternoon includes: ''UsingCrumb Rubber to Improve Wear 'Iblerance," presented by Dr.Jim Crum; "Landscaping Your Complex," Ron Crooker;"Aeration: Not Just for Compaction Relief," Jesse Cuevas.

The ISTMA Annual Membership Meeting is at 3 p.m., andwill be followed by an informal social time with hors d'oeuvres,rafiles and networking.

The sports turf session on Wednesday morning includes:

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FOR PRODUCT INFO FAXED TO YOU NOW! DIAL: 1(800) 817-1889

"Conversion from Artificial to Natural Turf- Kansas City Fields," presented byGary Custis; ''Ten Tips for ManagingFields on a Limited Budget," Dr. DaveMinner; ''I'm Not the Boss - What AreMy Responsibilities?" Jeff Salmond;''Managing and Its Role," Mike Burt.

For more information, contact LoriWestrum at The Turl Office: (515) 232-8222 (phone) or (515) 232-8228 (fax).

KAFMO: On February 19, theKeystone Athletic Field ManagersOrganization will hold seminars in con-junction with the PennsylvaniaRecreation and Parks Society. Furtherdetails will be announced soon.

For information, contact DanDouglas, Reading Phillies BaseballClub: (610) 375-8469, extension 212.

Florida Chapter #1: FloridaChapter #1 is planning a meeting forMarch 18 at Pro Players Stadium. Themeeting's focus will be field and equip-ment safety. Further details will beannounced soon.

For information, contact JohnMascaro: (954) 938-7477.

Northern California Chapter:

The Nor-Cal Chapter of STMA is plan-ning its 1998 schedule of events andwill announce details soon.

For more information about the Nor-Cal Chapter, contact Gail Setka at theDC Davis Grounds Office: (916) 752-5035 or fax to (916) 752-9631.

MAFMO: For information on theMAFMO Chapter or upcoming activi-ties, contact The Hotline: (410) 290-5652.

Colorado Chapter: For informa-tion on the Colorado Chapter or upcom-ing activities, call the 24-Hour CSTMAChapter HotlinelFAX: (303) 438-9645.

Minnesota Chapter: For informa-tion on the Minnesota Chapter or pend-ing activities, contact Connie Rudolph:(612) 646-1679.

Southern California Chapter:For more information on the SouthernCalifornia Chapter or pending activi-ties, contact The Chapter Hotline: (1-888) 578-STMA (toll free in SouthernCalifornia).

Chapters on the GrowArizona: For information on the

Sports Turf Managers Association ofArizona or upcoming events, con-tact Bill Murphy, City of ScottsdaleParks and Recreation Department:(602) 994-7954.

Mid-South Chapter: The newlyforming Mid-South Chapter ofSTMA will hold its next meeting inmid-February. More details will beannounced soon.

The Mid-South Chapter servesTennessee, Mississippi, Alabama,Arkansas, and parts of Louisiana,Missouri and Kentucky. For moreinformation, contact Chip Houmes:(901) 377-5081; or Jim Calhoun:(901) 755-1305.

Nevada: Plans are moving for-ward on the formation of a NevadaChapter of STMA. For informationon this developing chapter, contactIbsen Dow: (702) 649-1551.

Great Plains: For informationon the Great Plains Sports TurfManagers Association or upcomingactivities, contact MarkSchimming, City of Wichita: (316)337-9123. 0

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