wheat disease update may 19 - colorado state university...stripe rust and leaf rust in central...
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WheatDiseaseUpdate-May18,2019Dr.TessaAlbrecht,ResearchScientistandDiagnostician
DepartmentofBioagriculturalSciencesandPestManagementColoradoStateUniversity
MostofeasternColoradoisenjoyingaveragetoaboveaverageprecipitationandtemperaturesarealittlecoolerthannormal.InnortheasternColoradomuchofthewheatisbehindscheduleandstilljointingbutinthesoutheastheadinghasbegun.TherearestillnoreportsofstriperustinColoradohowever;inoculumisbuildinginourneighboringstatestotheeast.BobHunger(ExtensionWheatPathologistatOSU)observedstriperustandleafrustincentralOklahoma.ErickDeWolfreportsstriperustmovingclosertothewesternborderofKansaswithsevereinfectionsincentralKansas.LeafrustisalsoaffectingwheatinKansas.RustisnotaprobleminColoradoyetbutwithcontinuedprecipitationandcooltemperaturesitcandevelopquicklysokeepaneyeout.Wehaveseveralreportsoftanspotinthelowercanopy,whichiscausedbythefungalpathogenPyrenophoratritici-repentis.Tanspotsurvivesincropresidueandthrivesundercontinuousdampconditions.Leafsymptomsaresmalltanoval-shapedlesionsoftensurroundedbyayellowhalo.Centersoflesionsdarkenwithmaturity.Asthediseaseexpandslesionscoalescecausinglargeregionsofdiseasedtissue.Sporesaredispersedbywindaffectinglargerareasasthefungusisspreadtonewhosttissue.Managementoftanspotincludesfoliarfungicideapplications,geneticresistance,rotationwithbroad-leafplantsandcontrolofcropresidue.Keepinmindthishasonlybeenreportedonthelowerleavesofplantssuggestinglowtomoderateinfectionlevels.However,ifyouareconsideringfoliarfungicideapplicationtoinfectedfieldsErickDeWolfhasprovidedagoodresource:https://wheat.agsci.colostate.edu/wp-content/uploads/sites/85/2019/04/EP130.pdf.
Developingtanspotleafsymptoms
Wehavereportsofcephalosporiumstripe,causedbyfungalpathogenCephalosporiumgramineum.Initialinfectionsoccurinthefallandwinterinrootsofgerminatingwheat.Diseasesymptomsarelongyellowstripesalongtheveinsoftheleaves.Veinswillturnbrownasthediseaseprogresses.Aswithotherfoliarfungalpathogensthesporessurviveincropresidue.
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CulturalpracticesshouldbeusedtocontrolCephalosporiumstripesuchaslateplanting,controlofwheatresidueandrotation.Thereisnoapprovedchemicalcontrolforthispathogen.
Cephalosporiumstripeleafsymptoms
Wheatstreakmosaicvirus(WSMV)ispresentthroughouteasternColorado.WehavehadsamplestestpositiveforWSMVfromAdams,Bent,Larimer,Kiowa,KitCarson,Phillips,Prowers,SedgwickandYumaCounties.SamplesfromBentCountytestedpositiveforbothWSMVandTriticummosaicvirus(TriMV).ThereisalsoindicationofWheatmosaicvirus(WMoV),formerlyknownasHighplainsvirus.Thewheatcurlmite(WCM)transmitsallthreeoftheseviruses.SurveysarestillnotcompletebutWCMshavebeenfoundonsamplesfromAdams,LarimerandPhillipscounties.CulturalpracticessuchasgeneticresistanceandlateplantingareusedtocontrolforWCM-transmittedviruses.TherearealsoreportsofBarleyyellowdwarfvirus(BYDV)onwheat.Thisvirusistransmittedbyseveralspeciesofgrainaphids,butnottheRussianwheataphid.It’ssymptomsarecharacterizedbypresenceofaphidsandyelloworpurplishleaftips.Foliarinsecticidesareusuallynoteconomicallyfeasiblebecausemovementsofaphidpopulationsaresporadicandunpredictable.Foraguidetowheatdiseasesymptomspleasesee:https://wheat.agsci.colostate.edu/wp-content/uploads/sites/85/2019/04/EP130.pdfIfyouthinkyouhavediseaseinyourwheat,samplescanbediagnosedattheCSUPlantDiagnosticClinic:https://plantclinic.agsci.colostate.edu/