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Asian soybean rust identified in Louisiana

A day after Asian soybean rust was confirmed outside Baton Rouge, La., on Nov. 10, survey teams from USDA's Animal Plant Health Inspection Service began examining soybeans in fields within a 2.5-hour radius of the LSU AgCenter research farms where the disease was discovered.

The APHIS/ LSU AgCenter teams worked parishes in the immediate vicinity of Baton Rouge, located about 60 miles northwest of New Orleans on the Mississippi River.

“We're following our action plan,” said David Lanclos, Louisiana Extension soybean specialist. “The teams are made up of a couple of USDA/APHIS pathologists mixed in with researchers from the LSU AgCenter and the Louisiana Department of Agriculture. We're scrambling.”

The fields where the rust was originally found are some 10 miles apart — one at the St. Gabriel research facility and the other at the Ben Hur research farm 3 miles south of the LSU campus. Lanclos, who wasn't working the fields, wants to clear up errant reports that rust was found on research plots.

“These two fields have been erroneously identified as research plots. They are on research stations, true. But both are production fields.”

In neighboring Mississippi and Arkansas, news of Asian rust hit hard.

“Some of the Mississippi Department of Agriculture officials went to Baton Rouge yesterday (Nov. 10),” said Alan Blaine, Mississippi Extension soybean specialist. “More state ag department and Extension folks are (driving to the southwest part of the state) tonight so we'll be ready for some surveying tomorrow.”

The plan was to meet APHIS officials and farmers in the Woodville-Natchez area on Nov. 12, said Blaine. “We still have some late beans on fungicide test plots that haven't been harvested. We'll be checking those fields along with some kudzu in the extreme southern portion of the state. There's a lot of kudzu down there.”

Kudzu is one of the main alternate hosts of Asian soybean rust.

“Kudzu could become a big issue with this disease. This rust won't kill the kudzu like it will soybeans, though.”

Asian soybean rust is like other plant diseases, said Rick Cartwright, Arkansas Extension plant pathologist. “It turns out, for Asian soybean rust, soybeans are an economic host. But it has a number of wild hosts, including kudzu. It isn't the end of the world, though: people need to know that it's an ‘obligate’ parasite. That means if the host dies, the pathogen does too.”

Cartwright points to leaf rust in wheat as an example of what Asian soybean rust could bring to the country. “Leaf rust survives in south Texas, and every spring, by hopping from wheat field to wheat field, it begins moving northward. By the end of the summer, it reaches Canada. During the winter it dies out clear back to Texas again. I think Asian rust could be similar.”

In Arkansas, kudzu dies out every winter, so the rust couldn't live on it year-round, he said. What's concerning is farther south where volunteer soybeans or kudzu can live through the winter. “If it does get a foothold down there, like leaf rust, it would have to travel north annually,” said Cartwright. “I kind of expect this, over time, to become a conventional plant disease we have to deal with. In the beginning, it will be more challenging, but it isn't something to pack up and quit farming over.”

“To be honest,” said Chris Tingle, Arkansas Extension soybean specialist, “the last thing our growers needed was another problem. They've got enough as it is.”

Fungicides will keep the disease at bay, said Tingle. But if it gets into $5 soybeans, the economics will be “ugly. There was an expectation that we'd have an increase in soybean acres next season. Increased fertilizer prices were pushing more folks to say they were going whole-hog into beans next year. I don't know what they're saying now, but I'll bet they're rethinking things.”

Tingle points out that the United States is the last major soybean-producing country to see Asian soybean rust.

“For the past two years, the country has taken a proactive approach in dealing with this disease,” he said. “Arkansas has followed suit — as well as Mississippi and Louisiana — primarily because models indicated that the Mid-South would be one of the first areas it would be found. Lo and behold, the models were correct.”

The overall goal of the response plan is to prevent panic, said Tingle. “Panic, when you're dealing with a commodity, influences markets and retail sales. We don't want that. This is a sensitive issue: there are 3 million acres of soybeans in Arkansas. If the disease hits, it will change some people's lives.

Education is vital because Asian soybean rust easily can be confused with many diseases Delta farmers normally see.

“We need to prevent panic if someone finds bacterial blight and mistakes it for rust,” said Tingle. “We don't want anyone running through town yelling, ‘We've got rust!’ when he doesn't.”

Besides education, Tingle said the state is trying to get other defenses in line. “We've submitted numerous Section 18 requests to both the Arkansas Plant Board and to the EPA,” he said. “We need labels for at least seven additional fungicides. We've had research plots studying these fungicides over the summer.”

Those close to the action in Louisiana point to an active hurricane season as the likely deliverer of the disease. Cartwright doesn't doubt it. “The Louisiana coast is constantly buffeted by winds that have traveled thousands of miles. Who knows what those winds carry? The introduction of such things may happen frequently and we're just oblivious most of the time. Diseases may show up in a field or two and then die off and we never knew they were there.

“Weather events can be bizarre,” he continues. “You know, tornadoes can throw a fridge through a couple of buildings and the eggs inside won't be cracked. Knowing that can happen, it isn't all that odd to think spores can be carried on the wind a long distance.”

Before rumors of Asian rust “blew up,” Blaine said, plans were already under way to monitor the path of Hurricane Ivan (on the Alabama/Mississippi border).

“Just coincidentally, on Wednesday (Nov. 10) we made a trip to the coastal area looking at kudzu, what few beans are still in the field as well as some volunteer beans behind early plantings. We found nothing on the eastern side of Mississippi. That makes us feel good, lets us breathe a little easier.

“Now, we're going to meet APHIS on the western side of the state. I'm sure they've been doing a lot of surveying and trying to get a handle on how big an area to be concerned with immediately.”

While acknowledging the problem, Blaine made an effort to point out positives. “Everything isn't doom and gloom at this point. Every scenario doesn't point to disaster. If this disease had to come, it came at a good time. It's late in the year: we don't have to go into a major scramble mode and get something done in two days. Most of the crop is out and it'll have a minimal immediate impact, if any.”

And if the disease proves to be isolated around Baton Rouge, “we'll just pray for a good, cold winter down South,” said Blaine. “If enough of the alternate host is killed off so the rust can't survive, we could be back at square one next year.”

Until the disease was confirmed, many who had been tracking Asian soybean rust thought it would be years before it reached North America.

“It hit sooner than we expected,” admits Tingle. “We thought it would be a slow migration north since that's what was happening in South America. It only recently crossed the equator. From Columbia to Baton Rouge is a huge jump — that's not a slow migration at all.”


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