AUBURN, Ala.—Several weeks ago, Alabama Cooperative Extension System plant pathologists confirmed the presence of Southern corn rust in corn at the Gulf Coast Research and Extension Center.
With continued rains and several weeks of intense moisture, Alabama Extension plant pathologist Dr. Austin Hagan said producers should be scouting fields weekly in search of corn diseases.
“In the past few weeks, I’ve found common corn rust at Brewton, Headland and Tallassee,” Hagan said. “In addition, Southern Corn Leaf Blight has been particularly common at the Gulf Coast Research and Extension Center, along with Brewton and Tallassee.”
Recognizing Common Corn Rust
Common rust pustules are dark brown as compared with the orange to orange-brown coloration of southern rust pustules.
“Common rust pustules will be found in equal numbers on both leaf surfaces while southern rust pustules are more numerous on the upper leaf surface,” Hagan said. “Southern rust pustules are also in clusters of numerous pustules in comparison with the more solitary common rust.“
While common corn rust is still potentially damaging, it does not have the damage potential of Southern corn rust. This disease, like southern rust, is spread via frequent showers and weather systems moving from Mexico to Florida over the Gulf of Mexico. However, Hagan said common rust does not spread as fast, nor is it as damaging as Southern rust. Common rust is also active in “cooler” conditions than Southern rust.
Recognizing Southern Corn Leaf Blight
Hagan said this year Southern corn leaf blight lesions are larger and have a distinct lens shape with water-soaked margins and reddish brown coloring. This is differs from previous years when lesions were smaller, longer rectangles, appearing more tan in color.
Corn Disease Control
Hagan said there are a number of fungicides currently available for the control of rust in corn. These fungicides may help control other potentially damaging diseases like Northern or Southern corn leaf blight and gray leaf spot.
For assistance in the field, contact your local Extension office. For assistance identifying a corn disease, or disease on any other row crop, collect a sample and contact the Auburn University Plant Diagnostic Lab.