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