Asian soybean rust has been found in Louisiana kudzu in Washington, East Baton Rouge, Tangipahoa, Iberia and St. Mary parishes, but weather conditions will be the telling factor for the disease outlook in 2009, according to Boyd Padgett, LSU AgCenter plant pathologist.
“We see rust almost every year in these parishes near the Gulf,” Padgett said. “Growers don’t need to be complacent. They need to be vigilant.”
Cool days and nights will slow the fungus. “We have been fortunate since 2004 that the weather hasn’t been cooperative for a rust epidemic.”
Scientists believe dry conditions have suppressed the disease and kept it from spreading, but if a stable, favorable weather pattern for the disease lingers, it could continue to spread.
Kudzu is one of the host plants for Asian soybean rust, meaning the disease can survive on kudzu and spread to soybeans. If not caught early — when the disease spreads more slowly — rust can spread rapidly and destroy entire soybean fields.
Asian soybean rust was first discovered in the United States in 2004. Although it’s been known to exist since the early part of the 20th century, it was largely confined to Asia until recently — when it spread to Africa and then on to South America around 2000.
Since its initial discovery in south Louisiana in 2004, where its wind-borne spores are thought to have come in on storm winds that summer, it has been seen in kudzu and on soybeans in a variety of southern states, including Florida, Georgia, Alabama, Mississippi and Texas.
Padgett said rust already has been found this year in Alabama and Texas but not Mississippi.
The earliest the disease has been found in Louisiana in any year was Jan. 2, 2008, said Clayton Hollier, LSU AgCenter plant pathologist.
“It is surviving better this year than it ever has,” Hollier said. “Sites my associate, Patricia Bollich, has scouted have shown new growth of kudzu, new pustule formation and viable spores. What this ultimately means, we are not sure yet because there is still the possibility of a freeze.”
First symptoms of rust can only be seen by carefully looking at the lower leaves — by scouting fields often and thoroughly.
In addition to Asian soybean rust, producers also can face other plant diseases such as aerial blight, Cercospora, pod and stem blight and anthracnose.
Proper disease identification is the first step to an effective management strategy, Padgett stressed. “Knowing what’s affecting your crop will determine what treatments you implement. This can save producers time and money.”
Extension agents in LSU AgCenter parish offices can help soybean producers with identifying diseases and with recommendations about specific materials to use in combating those diseases. Also, a rust hot line will soon be activated for the third year in a row so people can call any time of the day or night, toll-free, to find out the status of the disease.
Plant pathologists from Mississippi State University and the University of Arkansas also will provide updated information about their respective states on the hotline.