Experts, U prepare for soybean disease

by Sam Boeser

Since the discovery of Asian soybean rust this November in Louisiana, the University has been working with Minnesota farmers and soybean experts to prepare the state for the arrival of the disease.

Soybean rust is a defoliating disease in soybean plants that kills plant leaf tissue. The disease does not kill the plant, but it greatly reduces seed yield because of defoliation. Farmers harvest the soybean seed.

If the disease spreads into Minnesota, it could significantly threaten the crop, which is important to the state. Minnesota is the third-largest soybean producer in the country, said Seth Naeve, a University soybean specialist

Sherri Lowe, director of communications for the Minnesota Soybean Growers Association, said, “We have been planning for this for two to three years.”

Naeve said, “From the number of states that have found it, it’s safe to say that the disease is pretty well established here.”

Its recent arrival in the Southern states might have been helped along by an increased number of hurricanes this year, he said.

Soybean rust does better in warm climates, which might help limit its damage in Minnesota.

“Our environment is less conducive to the growth of the disease,” Naeve said. “But because it moves so fast and has a quick generation time, it will still be an issue every year.”

The disease spreads primarily by releasing spores which are then carried by the wind. It’s possible Asian soybean rust could be in Minnesota as early as next year, he said.

Farmers across the state are preparing to battle the disease using fungicides, even though fungicides aren’t usually used in soybean farming, Naeve said.

Currently, farmers can pick from five Environmental Protection Agency-approved soybean rust fungicides, with more anticipated to be approved soon, Lowe said. It costs farmers approximately $25 an acre to treat crops with approved fungicides.

One problem with the increased use of fungicides is that fungi can build up resistance to them. To counteract this, researchers recommend that farmers rotate the fungicides they use, Naeve said.

Once a field is infected with the disease, however, using fungicides is ineffective, he said.

“Fungicides are protectants, not eradicants,” Naeve said.

The state and the University are working with soybean associations from across Minnesota to help detect the disease early. A team of experts who can identify soybean rust will be present in each county and will be organized through the University, Naeve said. Farmers who think their fields are infected can call a team member, who will look at the field and verify whether the disease is present, he said.

Their job will be important because soybean rust’s early symptoms often appear similar to symptoms of other soybean diseases, he said.

In the United States, soybeans are an $18 billion commodity, $1.3 billion of which comes from Minnesota, Naeve said.