common corn diseases in tennessee - ut cropsutcrops.com/corn/corn_images/corn diseases in...
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Common Corn Diseasesin Tennessee
Heather M. Kelly
Extension/Research Plant Pathologist
University of Tennessee
~ Disease favored by warm, wet/humid conditions~ Overwinters in corn residue~ Can be problematic in continuous corn~ Small lesion develop initially on lower leaves and elongate parallel to leaf veins (rectangular spots)
Gray Leaf Spot (GLS)Cercospora zeae-maydis
Northern Corn Leaf Blight (NCLB)Exserohilum turcicum
Most damaging if: ~Prolonged periods of dew and moderate temp. (64 - 80°F)~Infection before silking
Northern Corn Leaf BlightHelminthosporium turcicum
Common RustPuccinia sorghi~ Disease favored by cool (65-70°F), humid conditions~ Spores blown in from the South. Does not commonly effect yield in TN
Foliar Corn Diseases
Common Rust(Puccinia sorghi)
• Disease favored by cooler temp (65-70°F)
• Brown, elongated ½ - inch pustules on both sides of leaf
• Rarely causes yield loss
Southern Rust(Puccinia polysora)
• Disease favored by warm temp (77-82°F)
• Orange, round 1/16 -inch pustules primarily on upper leaf surface
• Can cause yield loss
Upper side of leaf
Lower side of leaf
Know the difference between rusts!
Common Rust
– Cooler temperatures (61-77 F)
– ½ in. brown, elongated pustules
– On both sides of leaf
– No yield loss
Southern Rust
– warmer temperatures (77-82 F)
– 1/16 in. orange, round pustules
– On upper leaf surface
– Fungicide application/resistant hybrid recommended to prevent yield loss
Upper side of leaf
Lower side of leaf
Holcus Spot OR Paraquat/Gramoxone Drift
• Both disease and drift have same lesion symptoms
• Both occur early in season
• Holcus spot caused by bacteria and prolonged wet weather with warm temp (76-86 °F)
With either no action needed, no yield loss usually occurs