IsWaterStuckonItsPerch?

Weather

Whatasummeritwas!Okaytechnicallysummerisn’toverifyou’reanastronomist.However,mostwouldratherthemeteorologicaldefinitionofSeptember1signifyingthebeginningoffallsincebothusandthegrasscouldusesomerecovery.Junehadallthehallmarksofstartingadroughtakinto2012,thenflippedcompletelyintoawashout.July–August2016willfallinthetop5wettestthatMissourihasexperienced.Alongwiththerainfall,intensehumidity,similarto2010and2011,plaguedtheregion.

IsWaterStuckonItsPerch?

StagnantGulfofMexicoairmasses,combinedwiththeaddedhumidityfromevapotranspiration,resultedinabrutalmixofhumid,andconstantlywarmair.Theaverage2016summerdewpointtemperatureforMissouriisinthetop4sincerecordswerekeptin1920.Thishumidairdidafewthings.Alongwithus,thehumiditymadeplants,particularlyshortonesonputtinggreens,veryuncomfortable.Plantsneedtoperspire,ortranspire,inordertokeepcool,andallthatexcesswatervaporalreadypresentintheairslowsthisevaporationprocess.Wetwiltwasacommonoccurrence,asgrassescouldn’ttakeuporgetridoftheamountofwaterneededtocoolthemselvesoff(seethispreviousupdateforinfoonthiscondition).Second,thehumidityputadamperonthedailyhightemperature,whichwasaboutaveragein2016,butheldtheheatlikeaplasticbagatnight.TheaveragelowtemperatureinJune-August2016was67.2F,3.1degreesaboveaverageandthe4thhighestonrecordtiedwith1954.Sincewaterthatgetshottendstostayhot,soiltemperaturesaveraged90degreesonmanydays.Ahistoricallybadsummerforcoolseasonturfgrass,specificallybentgrassandlowmowedtallfescue/Kentuckybluegrasssportsfieldsorlawns.Theforecastdoesofferawelcomeglimpseoffalltemperaturesandfallrecovery.TemperaturesareexpectedtobemildinthemiddlepartofSeptember,alongwithsomehealthychancesforparticipation.Rememberoneofthemainadvantagesofcoolseasonturfgrassesistheycanbeseededandforthemostpartquicklyestablishedcomparedtowarmseasonspecies…sodoit.

IsWaterStuckonItsPerch?

QuickHits:

• Aerification/Seeding/Fertilization:Thegreenflagisfinallywavingfortallfescuelawnsandsod,Kentuckybluegrassand/ortallfescuesportsfieldsandbentgrassfairwaysorputtinggreens.WehavefinallyreachedthemagicalSeptemberwindowformakinglong-termimprovementstocoolseasonturfgrassareas.Aerification,verticutting,orpowerrakingisagreatprecursorforrenovatingasite,ensuringgoodseed/soilcontactandobtainingasubsequenthealthystandofseedlings.Ataminimum,lowerthedeckfornormallyhighcuttallfescueorKBG(won’thearthatagainexceptforthisuse)tocreatesomespace.Fertilize,water,andletnaturetakeitscourse.Coolseasonannualweedswillbeinplaceandgerminating,whynotputsomecoolseasonturfgrassupagainstit?Onthatnote,payattentiontothelabelsforseedingeitherbeforeorafterherbicideapplication.SeedingfirstnowandapplyingherbicideinmidtolateOctoberisinmostyearsthebestrecourse.Asfarasfertilizationgoes,whetherseedingornot,nowisthetimetofeedcoolseasonturfgrasses.Dr.BradFresenburghasdevelopedafantasticwebbasedapplicationthatwillhelpdeterminetheamountoffertilizerrequiredforacertainarea,includingalinktoaGPSreferencedareaestimator.Designedforhomeowners,butcanbeaveryhandytooltocheckyourownapplications.Checkitoutathttp://agebb.missouri.edu/fertcalc/.

• GrayLeafSpothasprobablybeenworkingforafewweeksnow,butsymptomsconsiderablyflaredupoverthelastfewweeks.Grayleafspotismostsevereonperennialryegrassseedlings,particularlyonsportsfieldswhereitmaybebeingusedasaquickpatchforwornareas.Sometallfescuevarieties,particularly

IsWaterStuckonItsPerch?

‘Kentucky31’andthe‘Rembrandt’shownaboveareparticularlysusceptibletothedisease,butthereisnocompletelyresistantcultivar.Onestablishedtallfescuelawns,thediseaseismostcommoninsouthernMO,butcanoccurinabrutallyhotandhumidsummerlikethisinmidMO.Reducingleafwetnessthroughearlymorningirrigationanddewremovalpracticesarecriticalforcontrollingdiseaseoccurrenceandspread.Aswithseveralotherdiseases,applyingnitrogeninlatespringorsummercanenhancediseaseseverity.Fungicidestargetingthisdiseaseonlawnsisnotnormallysuggestedduetothesporadicnatureofdiseaseoccurrence.Thebestrecourseistooverseedthinnedareaswhentemperaturesmoderate.Onsportsturf,fungicidessuchastheQoIs(i.e.Compass,Insignia)andthiophanatemethyl(3336)maybeusedpreventively.Inacurativesituation,afungicidetank-mixorcombinationproductisrecommended.Careshouldbeexercisedwithmultiplefungicideapplications,asbothQoIandthiophanatemethylfungicideresistancehasbeendetectedinpathogen(Pyriculariagrisea)populations.

• Anthracnose:Asisoftenthecaseinlatesummer,anthracnosehasmadeacrashingappearanceinseveralsubmittedbentgrassandPoaputtinggreensamples.ThediseaseismoreprevalentonPoaannua,butwillinfectcertaincreepingbentgrassvarietiessuchas‘Penncross’,‘Pennlinks’,and‘SR1020’.Thelatesummer/earlyfalltimingofanthracnoseoccurrenceisduetoaweakenedplantafteralong,hotsummer,andahighernitrogenrequirementfromthefirstblastofmildertemperatures.Incurativesituations,atank-mixproductsuchasBriskwayorLexiconisrecommended,orasystemic(i.e.QoI,Velista,orDMI)pluscontact(chlorothalonilorfludioxonil).Aswithgrayleafspot,pathogen(Colletotrichumcereale)populationsresistanttoseveralfungicideclasseshavebeendetected,soa

IsWaterStuckonItsPerch?

carefulrotationstrategyshouldbeemployedinmultipleapplicationsituations.IsWaterStuckonItsPerch?

Many,manyputtinggreensampleshavebeensubmittedfordiagnosisthisyear,andmosthavehadonethingincommon–asaturatedrootzone.Asstatedabove,theenvironmentalconditionshadquiteabittodowiththis,sincehot,humidconditionsdidn’tallowbentgrassrootstoeffectivelytakeupthewateranddispelit,whilethecloudswereoftenverygoodatoverdispensingH20.Organicmatteraccumulationfromretreatingrootsandstolonscompoundedtheproblembyholdingontowater.Thecommonrecommendationistotine,tine,tine…toreleasepotentiallyhot,suffocatingwateroutofthesaturatedsoilprofileandprovidealesshospitableenvironmentforpathogens.Insomeofthesecases,however,perhapsthesubmittedsamplescan’ttellthewholestory.Thedepthofsamplesisnormally4inches,andinsummersliketheseonlyaninchortwomaycontainviableroots.Iftheproblemismoredeeplyrooted,say10–16inchesbelowtheturfsurface,therealcauseoftheconstantlysaturatedsoilismoredifficulttodecipher.AcollapsedPVCplasticdrainagepipeisoftenblamedasapotentialculprit,andcamerascopesareusedtoinvestigateanddetermineifit’sthetrueproblem.Thequestionthatislessoftenansweredis“Doestheentirecolumnofsoiloperatelikeaperfectflowingtubetothedrainagepipe?

IsWaterStuckonItsPerch?

TheUSGAputtinggreenprofileisnotaflowingtubeandisn’tdesignedassuch.Thepeagravellayerunderneaththesandservestoprovideaperchedwatertable,holdingareserveforpotentialrootuseuntilgravityovercomesthewaterholdingforce,priortocompletesaturation.Whengravitytakesover,avacuumpullfromthedrainagepipecandraintheprofilequickly.Somesaturatetherootzoneonpurposeintermittentlythroughouttheseasonto“flush”potentialsaltsorcontaminants,particularlyinaridregionspronetosaltaccumulation.ResearchattheUniversityofWisconsinbyDr.DougSoldatandUniversityofNebraskabyDr.BillKreuserandhisPhDstudentGlenObearhasuncoveredaprobleminseveralUSGAputtinggreenscausedbytheformationofimpermeableiron-oxidelayers(clickheretoreadmore).Thisissueisoccurringnearthesand/peagravelinterfacewherewaterandpotentialcontaminantsmayaccumulate.Thisresearchisongoingandhopefullythescopeoftheproblemandpotentialanswerscanberealized.Thefindingbegsthequestionthough,howmuchdocontaminantsplayaroleinplugginguptheUSGAsandprofile,andwhatinputsmaybecausingtheiraccumulation?Ifwatersitsontopofthisperch,isitcontributingtoananaerobic(ordeadbird)statedeepintheprofileandwhatharmmaythisbedoingtotheabovebentgrass?Weoftenassociateturflossatgreenmarginsandcollarstoincreasedtrafficfrommowerorgolfers,withtheworstdeclineoftenatthelowestpointsofthegreen.Perhapsthelateralsubsurfaceflowofwater,however,iscausinganincreasedaccumulationofwaterandflow-inhibitingcontaminantsinthisregionnearthegravellayer.Additionally,aheaviertexturedsoilservesasaboundaryononeside,soifthewaterisalsosealedbelowwheredoesthissubsurfacewatergo?Sittingwaterresultsinanaerobicconditions,andpotentiallyasulfur/methaneproducingblacklayerregionreleasingtoxicgasupwards.Additionally,acompletelysaturatedrootzonethatdoesn’tdraineffectivelywouldbeaprimegroundforPythiumrootrotandothersoilbornediseases.Manymorequestionsthananswersarepresentedhere,butafteranintensesummerlikethispastone,perhapsitisnecessarytodigalittledeeper.Withthebrutalenvironmentalconditionsthisprevioussummer,bentgrassputtinggreensneedednoextrahelpindeclining.Perhapsthewholesolutioncan’tbeachievedfromactionsonthesurface,andthetrueproblemliesfartherbeneaththesurfacethanwethink.LeeMillerFollowonTwitter!@muturfpathLikeonFacebook!MizzouTurfgrassExtensionTurfgrassPathologist-UniversityofMissouri