corn leaf with southern rust
Figure 1. Southern rust of corn
Market Journal Aug. 1, 2014 segment

Original content created by Dr. Jim Stack, former UNL Extension Plant Pathologist currently Kansas State University Extension Plant Pathologist.  Content edited and approved by Dr. Tamra Jackson, UNL Extension Plant Pathologist.


Puccinia polysora Schwein. Fungal structures include, hyphae, urediniospores (produced within uredinia), and teliospores (produced within telia). As the season progresses, both urediniospores and teliospores can be produced in the same rust pustule. The asexually produced urediniospores are dispersed long distances and are responsible for the spread of rust from the deep south to the Northern Great Plains in years where epidemics occur. Teliospores are not important in disease development.

Southern rust occurs commonly in the southeastern United States and periodically throughout the rest of the corn belt. This pathogen does not overwinter in Nebraska. Disease occurrence in Nebraska is dependent upon wind dispersal of urediniospores from southern states in early to mid July. Several different races of the pathogen exist.

Urediniospores Uredinia
uredinoospores image
uredinia image
Teliospores Uredinio and Telio
teliospores image
uredinio and telio image

Disease Symptoms

Early lesions on leaves are small and circular-to-oval, often with a prominent light green to yellow halo. As lesions mature, the fungus erupts through the leaf surface (epidermis. Light orange to cinnamon-red pustules (image) are the characteristic symptom on leaves; urediniospores that rub off on fingers are what impart the color to the lesion. Southern rust lesions are usually smaller than common rust lesions; common rust lesions are usually more elongate than circular. Unlike Common Rust of Corn, lesions of southern rust develop primarily on the upper leaf surfaces. Lesions develop on stalk, husk, and leaf sheath tissues as well. Under favorable weather conditions, leaves can be covered with lesions resulting in a leaf blight. Spores are wind-blown with new infections occurring every 7 days. As the season progresses, black teliospores are produced in a ring around the lesions.

Early Lesions Yellow Halo
early lesions image2
yellow halo image2
Leaf Surface Common Rust Lesion
common rust lesion image
Husk Leaf Blight
husk image
leaf blight image

Favorable Environmental Conditions

Southern corn rust has been confirmed in counties highlighted in red.

High temperatures (80°-90° F) and high humidity favor disease development.


Genetic Resistance

Resistant varieties are the most cost-effective means to manage southern rust in field corn. In seed production fields, foliar fungicides may be cost-effective if southern rust is severe. Consult your seed dealer to determine the best hybrids and inbreds for your area.

Chemical/Biological Control

Foliar fungicides can be effective in managing southern rust and numerous products are labeled for use.


For additional information, see the UNL Extension NebGuide, Rust Diseases of Corn in Nebraska (G1680).