Gray Leaf Spot

Overview

Gray leaf spot (Cercospora zeae-maydis) is a significant fungal disease affecting corn and other crops in the United States and Canada. This disease primarily targets corn, causing lesions on the leaves that can coalesce and lead to extensive leaf blight. The characteristic symptoms include rectangular, gray to tan lesions with distinct margins. Severe infections can result in premature leaf senescence, reduced photosynthetic capacity, and ultimately lower yields.

Gray leaf spot thrives in warm, humid conditions, making it particularly problematic in the Midwest and Eastern United States. The disease can also affect other crops like sorghum and certain grasses. Effective management is crucial to minimize its impact on crop health and productivity.

Farmers can manage gray leaf spot through integrated pest management strategies, including crop rotation, resistant hybrids, and timely fungicide applications. Products like GCS Azoxyprop, Headline AMP® fungicide, and Quilt Xcel® are effective fungicides available from FBN that can help control this disease and protect crop yields.

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How to Identify Gray Leaf Spot

Identifying gray leaf spot (Cercospora zeae-maydis) involves recognizing specific symptoms and signs on the affected plants, primarily corn. Here are detailed characteristics to help farmers identify this fungal disease:

Symptoms:

  1. Lesions:

    • Shape and Size: Lesions are typically rectangular and can range from 1/8 to 2 inches in length.

    • Color: Initially, lesions are small, yellow to tan spots. As they mature, they turn gray to tan with distinct, dark brown to purple margins.

    • Location: Lesions usually start on the lower leaves and progress upward as the disease advances.

  2. Leaf Blight:

    • Coalescence: In severe cases, lesions can coalesce, leading to large areas of blighted tissue.

    • Premature Senescence: Extensive leaf blight can cause premature leaf senescence, reducing the plant's photosynthetic capacity.

  3. Spore Production:

    • Appearance: Under humid conditions, gray leaf spot lesions may produce grayish spores on the leaf surface, which can be seen with a hand lens.

Scouting Tips:

  1. Timing: Begin scouting fields in mid to late summer, especially during periods of warm, humid weather, which favor the development of gray leaf spot.

  2. Field Edges and Low Areas: Pay particular attention to field edges and low-lying areas where humidity tends to be higher.

  3. Sampling: Inspect multiple plants across different areas of the field to get a comprehensive assessment of disease presence and severity.

Diagnostic Confirmation:

  1. Microscopic Examination: For definitive identification, a microscopic examination of the spores can be conducted. The spores of Cercospora zeae-maydis are long, slender, and multicellular.

  2. Laboratory Testing: If uncertain, samples can be sent to a diagnostic laboratory for confirmation.

Management:

  1. Resistant Hybrids: Planting resistant corn hybrids can reduce the impact of gray leaf spot.

  2. Crop Rotation: Rotate crops to reduce the inoculum levels in the field.

  3. Fungicide Applications: Use products like Headline AMP® and GCS Azoxyprop to manage the disease.

By closely monitoring these symptoms and implementing timely management practices, farmers can effectively identify and control gray leaf spot to protect their crops.

Photo Credit: Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org

Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org

Geographic Impact of Gray Leaf Spot

Gray leaf spot (Cercospora zeae-maydis) has a significant geographic impact across various regions in the United States and Canada, particularly in areas where corn is extensively grown. This fungal disease thrives in warm, humid conditions, making it especially problematic in the Midwest and Eastern United States.

Photo Credit: Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org

Paul Bachi, University of Kentucky Research and Education Center, Bugwood.org

Timing of Gray Leaf Spot Impact

Gray leaf spot (Cercospora zeae-maydis) typically emerges and impacts fields across the United States during the warm, humid conditions of mid to late summer. This fungal disease primarily affects corn but can also impact other crops like sorghum and certain grasses. The disease thrives in regions with high humidity and warm temperatures, making it particularly problematic in the Midwest and Eastern United States.

Photo Credit: Don Ferrin, Louisiana State University Agricultural Center, Bugwood.org

Don Ferrin, Louisiana State University Agricultural Center, Bugwood.org

How to Manage Gray Leaf Spot

Farmers can manage gray leaf spot in various crops using fungicides available from FBN. Here are some recommended products and their details:

GCS Azoxyprop

  • Active Ingredients: Azoxystrobin and Propiconazole

  • Crops: Labeled for use on corn, rye, and soybeans.

  • Application Rates:

    • Corn: Typical application rate is 12 oz/acre (range: 10.5-14 oz/acre).

    • Rye: Typical application rate is 18 oz/acre (range: 14-26 oz/acre).

    • Soybeans: Typical application rate is 16 oz/acre (range: 10.5-21 oz/acre).

Quilt Xcel®

  • Active Ingredients: Azoxystrobin and Propiconazole

  • Crops: Labeled for use on corn and sorghum.

  • Application Rates: Please check the label for specific application rates.

Headline AMP® fungicide

  • Active Ingredients: Metconazole and Pyraclostrobin

  • Crops: Labeled for use on corn and other crops.

  • Application Rates: Please check the label for specific application rates.

Implementing these fungicides as part of an integrated pest management strategy, including crop rotation and resistant hybrids, can help mitigate the impact of gray leaf spot on crop health and productivity.

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Every product that labels GRAY LEAF SPOT as a weed, pest, or disease the product can be applied against is shown below. Click any product for label and more information.
3336 Plus™3336® DG Lite®3336® EG3336® F3336® WPA-Zox 25SCA-Zox 50WDGAbsolute® MaxxAcadia® ESQAcadia™ 2 SCAcadia™ 2 SCAcadia™ ESQ FungicideAdastrio™Affiance®Affiance™Affirm™ WDGAframe™Aframe™ PlusAftershock®Andiamo® 230 FungicideAndiamo™ 230 FungicideAproach®Aproach® PrimaAprovia® Top FungicideAquila™ XLAriston®Arius™ 250Armada® 50 WDGArmada® 50 WDGArmada® 50 WPArysta Propiconazole 41.8 EC FungicideAstera™ Fungicide with aßpro™ Yield EnhancerAvaris® 2XSAvaris™ FungicideAviv™Aviv™Azoxy TebAzoxyStar®Azoxystrobin SCAZterknot®AZteroid® FCAZteroid® FC 3.3Azure™ Xtra FungicideBacixBanner MAXX®Banner MAXX® IIBarrierBasic Copper 53Bayleton® 50 Turf and OrnamentalBayleton® FloBravo Ultrex®Bravo Ultrex®Bravo Weather Stik®Bravo Weather Stik®Bravo® SBravo® ZnBravo® ZN Agricultural FungicideBriskway®Brixen™ FungicideBrixen™ FungicideBumper®Bumper® 41.8 ECBumper® ESBuzz Ultra - DFBuzz Ultra DF™Caramba® fungicideCarb-O-Nator®Catamaran®Cercos™ FungicideChloronil® 720Chlorothalonil 720Chlorothalonil 82.5DF SelectChlorothalonil-ZnClearscape Turf and Ornamental FungicideCOC DFCompass®Concert®Concert® IIConfine® ExtraConfine™ Extra T&OCover XL (Agri Star)CrossoverCrossover® ProCueva® Fungicide ConcentrateCustodia®Cymbol™ AdvanceDaconil Ultrex® Turf Care®Daconil Weatherstik®Daconil® Action™Daconil® WeatherStik®Delaro® 325 SC FungicideDelaro® CompleteDensicor®Densicor®Dexter® SCDexter™ MaxDexter™ XCELDisarm® 480 SCDisarm® C FungicideDisarm® G FungicideDisarm® MDithane® 75DF Rainshield® Specialty FungicideDithane® F45 Rainshield® FungicideDithane® M45 FungicideDocket® DFDocket® WSDomark® 230 MEDomark® 230 ME FungicideDornic™ 720 FE-Scape ETQ® Turf FungicideEagle® 20EW Specialty FungicideEcho Dyad ETQ®Echo® 6F ETQ™Echo® 720 Agricultural FungicideEcho® 720 Turf and Ornamental FungicideEcho® 90DF Agricultural FungicideEcho® Ultimate ETQ™Echo® Ultimate Turf and Ornamental FungicideEcho® Zn Agricultural FungicideElatus® FungicideElloraEluvium™Encartis™ fungicideEndorse® Wettable Powder FungicideEndow™ GEnsign® 720 Flowable FungicideEnsign® 82.5% Turf And OrnamentalEquation™ SC FungicideEquus® 500 ZNEquus® 720 SSTEquus® 720 SSTEquus® DFEvito® 480 SCEvito® T FungicideExteris® Stressgard®Fitness® FungicideFlint® ExtraFlint® FungicideFore® 80WP Rainshield® Specialty FungicideFortix® FungicideFortuna™ 75 WDG FungicideFungo® FloGavel® 75DF FungicideGCS Azoxy 2SCGCS AzoxypropGCS Tebustrobin SCGem® 500 SCGold Rush®Guarda®Headline AMP® fungicideHeadline® fungicideHeadline® SC fungicideHeadway®Headway® GHelmstar Plus SCHeritage® FungicideHeritage® GHeritage™ ActionHeritage™ TLHonor® Intrinsic™ brand fungicideHonor™ fungicideIncognito® 85 WDGInitiate® 720 Flowable FungicideInitiate® ZNInsignia® fungicideInsignia® SC Intrinsic® brand fungicideInspire Super®Instrata®K-Phite® 7LP Systemic Fungicide BactericideK-Phite® 7LP T/OKOP-Hydroxide™KOP-Hydroxide™ 50WKoverall® FungicideKoverall® FungicideLexicon® Intrinsic® brand fungicideLucento™Luna Sensation®Luna® FlexLuna® TranquilityMagistrate™ManKocide®Manzate® MaxManzate® Pro-Stick™ (UPI)Manzate® Pro-Stick™ T&OMarazo™Mazolin™Medallion® FungicideMettle® 125 MEMettle® 125 MEMettle® 125 MEMiCrop™ FungicideMiCrop™ FungicideMiravis® NeoMiravis® PrimeMiricell™Monsoon®Monsoon® TurfMural™Nordox®Nordox® 75 WGNu-Cop 50 WPNu-Cop® 30 HBNu-Cop® 3LNu-Cop® 50DFNu-Cop® HBNu-Cop® XLRNufarm Propiconazole SPC 14.3 MECNufarm T-Methyl SPC 4.5F FungicideNufarm T-Methyl SPC 50 WSB FungicideNufarm T-Methyl SPC Granular FungicideNufarm TM + CTN SPC 66.6 WDGObrona™Offset™ 3.6F FungicideOHP 6672™ 4.5 FOHP 6672™ 50 WPOmni® Brand Chlorothalonil 720SCOmni® Brand Propiconazole 41.8% ECOnset™ 3.6L FungicideOranil™ 6LOrius® 3.6FOrondis® Opti (Premix)Orondis™ Opti BOxiDate® 2.0OxiDate® 5.0Pegasus® 6LPegasus® DFXPenncozeb® 75DFPenncozeb® 80WPPeriapt™PeroxySan-CX Broad Spectrum Bactericide/FungicidePhoenix Kestrel® MEXPhoenix Pegasus® 6LPhoenix Pegasus™ DFXPhoenix Pegasus™ HPXPhoenix Peregrine®Phoenix Siskin®Phoenix Skylark™Phoenix T-Bird® 4.5LPPZ 41.8 Select™Praiz® NGPraiz™Preemptor® EQPreemptor™ SC FungicidePrevia®Priaxor® Xemium® brand fungicidePrimeraOne® Chlorothalonil 720 SFT FungicidePrimeraOne® Chlorothalonil DFProcon-Z™ FungicideProline® 480 SCPropazProPensity® 1.3ME Turf and Ornamental FungicidePropi-Star® ECPropicon ECPropiconazole 1.3 ME T&OPropiconazole 3.6 EC FungicidePropicure 3.6FPropiMax® EC FungicidePropulse®Prosaro® 421 SCProsaro® Pro 400 SCProtect™ DFProtegam® YLDProthioconazole 4L Select™Protocol®Prozio™ BWPProzio™ SCQuadris Top®Quadris® FlowableQuilt Xcel®Quilt® FungicideRegalia®Regalia® Rx BiofungicideRegev®Rendition™Resist 57™Revus Top®Revylok™ FungicideRevytek™ fungicideRhapsody®Rialto™ 720 FRidomil Gold® Bravo® SCRoper® DFRoper® DF Rainshield™RustEaseSatori® FungicideShar-Shield PPZSil-Matrix® LCSil-Matrix™Sipcam Clearscape® ETQ™ Turf FungicideSipcam Clearscape® Turf and Ornamental FungicideSlant™Slant™ ECSpectro® 90 WDGStratego®Stratego® YLDStrider™ FungicideT-Bird® 4.5LTalaris™ 4.5 FTalaris™ 50 WSPTarian™Tartan®Tartan® StressgardTartan® StressgardTebazTebu-Crop 3.6FTebu-Turf 3.6FTebucon® 3.6F FungicideTebuconazole 3.6F T&OTebuStar® 3.6LTebuzol® 3.6FTee-1-Up® WDGTee-Off® 4.5FTekken® Broad Spectrum FungicideTepera® PlusTepera® Plus HDTepera® Plus HDTepera™Tetraban®Tetraban® FungicideTide Propiconazole 41.8% EC FungicideTilt®Timorex Act®TM 4.5F Select™Token™ SCToledo®Topaz® FungicideTopguard®TopGuard® EQ FungicideTopguard® FungicideTorque™ FungicideTourney® EZ FungicideTourney® FungicideTraction™ FungicideTrevo®Trevo® DCZTrevo® PTrevo® TRZTriathlon® BATrivapro® FungicideTrivapro™ ATrivapro™ BUnicorn DFUnion™ Fungicide SCVabro™Vacciplant®Vacciplant®Vango™ ESQVango™ ESQ FungicideVeltyma® fungicideVeranda® T Water Dispersible GranulesVertisan®Viathon®Vibe™VigilWillowood Azoxy 2SCWillowood AzoxyProp XtraWillowood Propicon 3.6ECWillowood Pyrac 2ECWillowood Teb 3.6SCWillowood Tebustrobin SCXiphosin™Xyway™ 3D FungicideXyway™ LFRZing!®Zolera™ FX Fungicide