Occurrence of common rust has been reported in most corn-growing areas. Southern rust has been reported in Texas and further spread is likely. Common rust is favored by cool, humid conditions, found on upper and lower leaf surfaces, and distinguished by elongated red to cinnamon-brown pustules. Southern rust is favored by high temperatures and humidities, found on the upper leaf surface only, and more orange or reddish-orange in appearance.
Pustules are small and circular, with a pinhead appearance.
Distinguishing common rust from southern rust is important. Common rust rarely causes significant yield loss in hybrid corn, but severe southern rust can decrease yields. Fungicides may partially control common rust in corn, but in most cases are not economical in hybrid corn production. If fungicide use is justified, Tilt is recommended most often. Stalk quality is closely tied to leaf function.