Southern rust is caused by the fungus Puccinia polysora. Although generally considered a tropical disease, southern rust can occur in important corn production areas of the United States and Canada. Photo taken on Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

The damage to the plant is due to the loss of photosynthetic leaf area. The disease progressively worsens as the plant develops. This pathogen also infects other hosts including silver plume grass. Photo taken Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

Puccinia polysora produces dense uredial pustules on the surfaces of the corn leaves, leaf sheaths, and stalks. The uredia are small, 0.2-2.0 mm long nad circular to oval in shape. The color is orange-red to light cinnamon brown. The rust symptoms occur when the uredia break open and sporulate. Photo taken Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

The rust affects the lower leaves more than leaves further up the plant. Pustules of P. polysora are not as powdery initially as those produced by Puccinia sorghi (Common corn rust). Also, the development of dark colored teliospores around the pustule occurs later in the season than those of common corn rust. Photo taken Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

Favorable environmental conditions for disease development are altitude less than 700 meters, temperatures between 25 and 35 degrees Celsius, and high humidity. The uridiospores are the only type of spores known for this pathogen life cycle. Photo taken Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

Southern rust is now active on corn from Kansas to Indiana and southward. This disease used to arrive in Kansas around the first of August, but since 2015, it has been arriving much earlier. Photo taken Sept. 12th 2019. (Jordan Koster | Collegian Media Group)

The severity is dependent on the weather. Southern rust likes 90-degree days, warm nights, and high humidity. which is why it's most common in the tropics. Photo taken on Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

A few steps in managing Southern Rust are to till fields in the fall to bury crop residue. another step is to rotate fields for at least one year with crops other than corn. Photo taken Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

Some corn hybrids with common rust may produce yellow haloes around rust pustules making them more difficult to differentiate from southern rust. Photo taken on Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)

The first positive field in 2019 was discovered on July 11, but based on the age of the pustules, it has been here since sometime in mid-June. This, combined with very late-planted corn in many areas of the state, increases the threat that this disease will cause significant yield loss problems in 2019. Photo taken Sept. 12th, 2019. (Jordan Koster | Collegian Media Group)