Experts not taking soybean rust threat lightly

The approach to soybean rust resembles a build up of homeland security. Experts have seen its devastation in foreign lands and aren’t taking the potential for an invasion lightly.

Short of alarm, the strategic plan is to address the concerns of growers as much as it is a plan for after the rust arrives.

In the upper Southeast, as in other parts of the country, Extension experts, agents, consultants, state departments of agriculture, and USDA are preparing for an invasion. In the lower Southeast, the Florida Department of Agriculture has set out “sentinel crops” to have an early warning. Meteorologists are also involved in predicting when the disease might hit soybean fields in the United States.

Extension county agents, consultants and state department of agriculture agronomists will most likely encounter the disease first. In the upper Southeast, training at the county level is scheduled to help those workers distinguish rust from soybean rust and outline the protocol for determining if it is soybean rust. Virginia is scouting soybeans every two weeks. “One of the main reasons for scouting is to calm some of the fears that are out there,” says David Holshouser, Virginia Tech Extension soybean specialist.

“We’re in no big hurry to get the disease here,” says Jim Dunphy, North Carolina State University Extension soybean specialist. “If it’s as serious here as it is in other countries,” it could inflict serious economic damage to the U.S. soybean industry.

In anticipation of the fungicides needed to fight soybean rust, the Environmental Protection Agency has pushed through paperwork that would speed up the process of registering chemicals currently not labeled in the U.S. for soybeans, but that are registered in other countries for the treatment of soybean rust.

The devastating, airborne fungus has already cut a wide swath in soybean crops in Asia, Australia and Africa. Discovered in South America in 2001, it has already moved from Paraguay to near the Equator in Brazil. Last year, the disease cost Brazilian growers $1.3 billion in lost yield and chemical application. Ninety percent of Brazil’s soybean acreage had soybean rust last year.

U.S. researchers who have seen it call soybean rust a “very impressive disease.”

The consensus is soybean rust will arrive in the U.S., but how fast it will spread, or if the country will be able to manage its spread will involve “playing it by ear,” Dunphy says.

Soybean rust would not likely be able to withstand the winters of the Mid-Atlantic region, Holshouser says.

After traveling to Brazil in March, Holshouser says there’s a continuous source of inoculum in South America. “The disease never went away from what I saw,” he says. “I can understand why it’s so bad because of the continuous inoculate source. We were in a southern Florida type of climate.”

Soybean rust would likely have to be blown in by air, similar to how blue mold arrives in the U.S. from the Caribbean.

Only two fungicides are currently registered for soybean rust in the United States. Foreign countries have a larger chemical arsenal for treatment of soybean rust.

“We don’t have enough chemicals to treat 65 million acres of soybeans,” Dunphy says. “If rust gets confirmed in the U.S., the EPA will probably work with companies to clear additional fungicides that we have on the market for other crops, but aren’t yet cleared for soybeans. It’s almost a matter of having quantity of fungicides as it is quality. This is unique contribution from EPA’s standpoint to be able to go that far.”

In Zimbabwe, soybean rust wiped out 80 percent of the crop in some areas.

Because it’s already in South America, researchers point out that “one hurricane” could bring it to the United States.

Soybean rust causes legions on plants that can lead to premature defoliation and decreased yields.

“Scouting will become more important,” Dunphy says. “Soybean rust is a disease that can develop rapidly. Scouting will also be important from the standpoint of peace of mind. When we scout and don’t come up with soybean rust, there’s a little more confidence that it’s not there.”

It’s been known to take over plants in five or six days.

Agricultural workers at the local level will be the first responders, so to speak. If they spot something in soybean fields, they’ll then send it to a lab at the university level. If it looks like soybean rust, then the state laboratory will forward the sample to both the USDA-APHIS lab in Florida and Beltsville, Md.

“The proper authorities at the USDA-APHIS labs can identify it within a day if it is the soybean rust pathogen,” Holshouser says. “It won’t just be a visual observation, but a DNA-based diagnosis called Real-time Polymer Chain Reaction or PCR for short.”

For example, in North Carolina, South Carolina and Virginia county agents are being trained to detect the symptoms of soybean rust.

Virginia has hired an undergraduate student to scout fields in the state every two weeks for soybean rust. “He’s in the field right now scouting well over 60 fields every two weeks,” Holshouser says.

There’s a sense of urgency at all levels of agriculture about soybean rust. The North Carolina Soybean Producers Association, in conjunction with the American Soybean Association, the United Soybean Board, hosted the first of seven national informational meetings beginning in late July.

A fungus disease, soybean rust typically shows up on the undersides of leaves with tan to rust color. To the layman’s eye, it’s not that different from some other foliar diseases, Dunphy says, so it will take some expertise to diagnose.

It can be confused with a number of diseases, including brown spot, bacterial pustule and bacterial blight.

The questions rolling around about soybean rust in agronomy and plant pathology circles range from, “if it comes into the Southeast and works up the coast, do we have enough fungicides to deal with it right now?” to, “what happens if it comes up the Mid-South and goes up to the Midwest,” Dunphy asks. “That’s a different story because of the difference in volume of soybeans. Do we need enough fungicide to treat the Southeast or the Mississippi Valley and the Midwest?

“On one hand, we don’t want to get caught off guard and on the other hand, we don’t want to scream wolf,” Dunphy says.

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