Soybean Rust

For the most current information on Rust, visit the USDA's rust website.

For additional information:

visit the United Soybean Board website.


or visit the Stop Soybean Rust website.

Asian Soybean Rust has been identified in the United States. While the disease cannot overwinter in Pennsylvania, it may be able to travel north during the growing season. If soybean rust is confirmed in any neighboring states, please consult the links on this site, Cooperative Extension, and your crop insurance agent if applicable, for the proper course of action.

The Pennsylvania Soybean Promotion Board is urging farmers to learn as much as possible about soybean rust in preparation for its potential eventual arrival.

Soybean rust is caused by either of two fungal species, Phakopsora pachyrhizi, also known as the Asian species, and Phakopsora meibomiae, the New World species. The Asian species, the one found in Louisiana, is the more aggressive of the two species, causing more damage to soybean plants.

Soybean rust is spread primarily by wind-borne spores capable of being transported over long distances. Producers will need to watch for symptoms of the fungus such as small lesions on the lower leaves of the infected plant that increase in size and change from gray to tan or reddish brown on the undersides of the leaves.

USDA and the soybean checkoff have been cooperating on awareness efforts and will amplify those efforts now that the disease has been found in this country. Lesions are most common on leaves but may occur on petioles, stems, and pods. Soybean rust produces two types of lesions, tan and reddish brown. Tan lesions, when mature, consist of small pustules surrounded by slightly discolored necrotic area with masses of tan spores on the lower leaf surface. Reddish brown lesions have a larger reddish brown necrotic area, with a limited number of pustules and few visible spores on the lower leaf surface. Once pod set begins on soybean, infection can spread rapidly to the middle and upper leaves of the plant.

Soybean rust can be managed with the judicious use of fungicides. However, early detection is required for the most effective management of soybean rust. Monitoring soybean fields and adjacent areas is recommended throughout the growing season. Fungicide applications can reduce yield loss, depending on the plant developmental stage, time when soybean rust is detected, and fungicide application method. Efficacy information for producers on fungicides is available through state university extension services.