News that soybean rust was found in Louisiana Nov. 6 marked the first time the disease has been detected in the United States. That means that the industry will need to ramp up its education about the disease, government and university officials said.

On Nov. 10, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) confirmed the presence of soybean rust on soybean leaf samples taken from two plots associated with a Louisiana State University research farm four days earlier.

"The fact that it was found in the fall gives us the winter to prepare ahead of the 2005 growing season," said Kansas State University plant pathologist Doug Jardine. "We had an active education program last winter, but this winter we'll have to intensify it, because it's important to educate producers and ag industry personnel about the symptoms and management of the disease."

"We've been anticipating soybean rust's arrival in the United States, so we asked that EPA approve registering certain fungicides for use in Kansas," said Kansas Secretary of Agriculture Adrian Polansky in a release. "The disease can be managed with judicious use of fungicides."

In September, the Environmental Protection Agency granted emergency exemptions for five products to be used in Kansas. Approved were Tilt, PropiMax EC and Bumper, which contain propiconazole; Laredo EC and Laredo EW, which contain myclobutanil; and Folicur 3.6F, which contains tebuconazole.

Polansky encouraged growers to learn more about the disease, its symptoms and its management.

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.

The disease is spread by wind-borne spores capable of being transported over long distances. APHIS scientists believe that the disease was most likely brought into the United States by this year's active hurricane season, according to a USDA news release.

While the harvest for this year is complete, producers will need to watch for symptoms of the fungus that begin as small lesions on the lower leaves of the infected plant. These lesions increase in size and change from gray to tan or reddish brown on the undersides of the leaves. If the disease goes untreated, the plant may become entirely defoliated in 10-14 days.

The fungus resembles brown spot, a common disease in soybean, and the less common bacterial pustule, which might make it a bit difficult to diagnose, said Jardine, who is the state plant pathology leader for K- State Research and Extension.

"In a typical Kansas growing season, the southeast part of the state is the area most likely to have a problem with the fungus," Jardine said. "That's because the disease is favored by high precipitation and high humidity, conditions ideal for rust development. In addition, the disease likes cooler weather such as typically occurs in September and October in Kansas. I would expect the later-maturing variety soybeans, in the southeast particularly, could be vulnerable once fall sets in next year."

Generally, the rest of the state has relatively high summer temperatures and low to moderate rainfall and humidity, which should be less conducive for development of the disease.

"It's a good thing we didn't have it this past growing season, given the unusually cool, wet weather most of the state experienced this year," Jardine said.

Information about soybean rust is available at the USDA Web sites: http://www.aphis.usda.gov/ppq/ep/soybean_rust/ and http://www.aphis.usda.gov/lpa/issues/sbr/sbr.html.  Information is also available at http://www.planthealth.info and http://www.soybeanrustinfo.com .


Information was compiled from Kansas State University Research and Extension, U.S. Department of Agriculture and Kansas Department of Agriculture sources.

Soybean rust: what to look for and where it came from


News that soybean rust has been discovered for the first time in the United States heightens the need for awareness and education about the disease among agricultural producers and affiliated industries, said K-State Research and Extension plant pathologist Doug Jardine.

The following is information provided by the USDA and the Kansas Department of Agriculture about the disease and where it came.

What to Look For: Small lesions may be visible 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. 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.

Where Did It Come From? Asian soybean rust was first observed in Japan in 1902, and was found throughout most Asian countries and in Australia by 1934. It currently is found in Africa, Asia, Australia and South America. Because the disease spores are carried by the wind, it was expected to make its way to the United States from South America.

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus in Manhattan.