DATE: 3/16/2006

CONTACT: Dr. John Mueller, (803) 284-3343, ext. 223; jmllr@clemson.edu

WRITER: Tom Lollis, (803) 284-3343, ext. 241; tlollis@clemson.edu

Clemson expert hopes soy rust behaves the same as in 2005

BLACKVILLE – South Carolina farmers concerned about Asian Soybean Rust (ASR), a potentially devastating crop disease that is new to North America, have some reasons for optimism for 2006, according to a Clemson University scientist.

“If rust behaves the way it did in 2005, soybean growers should come out all right,” says John Mueller, plant pathologist/nematologist at Edisto Research and Education Center.

“Last year we never saw it before flowering in any field,” he said. “If it will do that again, we’ve got a good chance of going in and spraying fungicides once or twice, depending on rust pressure, and doing a good job of protecting everything.”

Mueller said that no one can predict what rust will do. His most likely scenario, however, calls for more rust than last year, unless the state goes through a drought.

“In that case rust will be a secondary problem,” he said. “Given a choice, I’d rather fight rust than drought.”

Mueller said that a big key to controlling ASR will be the 15 sentinel plots established around the state as an early warning system for growers.Every soybean grower should be within 50 miles of a monitoring site.

“If rust shows up in your area, don’t worry about it unless your soybeans are flowering,” he said. “If your beans are flowering and it’s going to be moist and rust is beginning to show up, that’s when you need to spray.”

“It will be important for growers not to begin believing that rust is overrated,” he said. “If that’s the attitude they take into this season, they will be in trouble. Prices are dropping and profit margins will be lower.”

Mueller said South Carolina producers spent at least $500,000 spraying for rust in 2005.

He encourages growers to keep track of rust developments through the USDA website at www.sbrusa.net and through his electronic newsletter. It will be sent out when needed. Growers can subscribe by sending an e-mail to jmllr@clemson.edu.

He thinks that the state came out of the winter fairly free of ASR because of killing frosts.

“We’ve had temperatures in the mid 20s. That’s more than enough to kill off any kudzu, an alternate host, or weeds where rust might overwinter,” Mueller said.

He noted that while the northern half of Georgia is pretty clean, it is possible to find rust on kudzu in south Georgia that has been protected from frost kill by cover from abandoned buildings and Interstate Highway overpasses.

“That’s one thing that’s different from last year, when kudzu didn’t develop rust until March,” he said.

Mueller said that a disease called frogeye leaf spot will make it harder to find rust, since symptoms are similar. He recommends planting soybean varieties that are resistant to frogeye.

He said that it should be easier to find rust this year since at least 75 persons in the state have been trained to recognize it.

Mueller advised growers not to plant more beans than they can spray in a timely manner.

“Once rust is in your field you want to spray with a triazole such as Folicur, Laredo or Domark. If rust is still 50 miles away and your Group VIIs are about to flower, I’d include a protectant in my spray. If you’re in St. Matthews and rust is in Hampton and the weather is perfect, I’d probably recommend a protectant,” he said. “The triazoles will not control the other diseases like frogeye, brown spot, pod and stem blight or anthracnose. If you’re aiming to control them, include a strobilurin in your tank – Headline, Quilt, Stratego, Quadris or combinations. Topsin M is effective on the other diseases, but not on rust.”

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