Soybean Rust Found in the United States

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Southern states' diagnosis create concern for Delaware soybean farmers

(DOVER) -Delaware Secretary of Agriculture Michael Scuse was notified by the United States Department of Agriculture Animal and Plant Health Inspection Service (APHIS) in November 2004 that Asian Soybean Rust has been found in the State of Louisiana. Soybean rust is a serious fungal disease that is principally spread by wind-borne spores that can cause significant crop losses.

According to the North Central Soybean Research Program, “The disease spreads quickly through a field planted with a susceptible variety, making it the most destructive foliar disease of soybean where it occurs. Yield losses where rust occurs range from 10-80%, depending on how early in the season the plant is infected.”

Secretary Scuse said, “Because Asian Soybean Rust is spread by wind-spores, I am not surprised that it has found its way into the United States, most likely from South America. My concern is that it might reach the major soybean growing areas in this country. Soybeans are Delaware’s major crop. Damage to the crop would not only have severe implications for our growers, but would seriously impact our poultry industry as well. In 2003, Delaware harvested 178 thousand acres of soybeans which yielded 36 bushels per acre. In 2004, farmers planted 207 thousand acres of soybeans and are expecting a yield of 42 bushels per acre. We are lucky that it arrived in the U.S. after most of the harvest has been completed. We have time to prepare for the next growing season.”

Scuse continued, “The Delaware Department of Agriculture (DDA), along with the Cooperative Extension, USDA APHIS, and industry representatives in the State, has been working for several months to prepare for the discovery of this fungus in the United States. We are developing a response and action plan for Asian Soybean Rust that will be presented on January 26 at the Soybean Education Conference. Also, the DDA Pesticide Section has asked for Section 18 specific exemptions for fungicides known to be effective against the disease. DDA has asked for and received approval from the EPA for the use of TILT, Propimax, Bumper, Laredo, and Folicur. These fungicides are to be used only if the Asian Soybean Rust is present in the state.”

When notified about the presence of the disease in the U.S., Jeff Allen, President of the Delaware Soybean Board said, “The Delaware Soybean Board will lend its support and funding to ensure that Delaware growers are knowledgeable of the disease and the actions to be taken if they suspect an infection in their fields. We will do everything possible to assist the Delaware Department of Agriculture, the University of Delaware, and others involved, should soybean rust be found in our state.”

Growers and others interested in finding out more about Asian Soybean Rust are invited to attend the Soybean education workshop on January 26, sponsored by the Delaware and Maryland Soybean Boards. The workshop is being held in conjunction with Delaware Agronomy Conference on January 26-27, 2005 in the Exhibit Hall at the Delaware State Fairgrounds in Harrington, Delaware.

USDA Press Release:

USDA CONFIRMS SOYBEAN RUST IN UNITED STATES

WASHINGTON, Nov. 10, 2004 – The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service today confirmed the presence of soybean rust on soybean leaf samples taken from two plots associated with a Louisiana State University research farm Saturday.

While this is the first instance of soybean rust to be found in the United States, the detection comes at a time when most soybeans have been harvested across the country. As a result of the harvest, the impact of the fungus should be minimal this year.

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.

USDA will dispatch its soybean rust detection assessment team, composed of scientific experts and regulatory officials, to the site within 24 hours. The assessment team will work closely with Louisiana State Department of Agriculture representatives to assess the situation and conduct surveillance around the detection site to determine the extent of the disease spread.

Soybean rust is spread primarily by wind-borne spores capable of being transported over long distances. At this point in time, based on predictive models, APHIS believes that the detection in the U.S. is related to this year’s very active hurricane season. While the harvest for this year is complete, during next year’s planting season, 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 industry 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.

For more information, visit APHIS’ soybean rust “hot issues” Web site.