In mid-November, with Louisiana and Mississippi having confirmed Asian soybean rust within their borders, scout teams and researchers fanned out across the South to see how far the wind-borne disease had spread. It didn't take long to add more states to the list of infected.
On Friday, Nov. 19, the USDA confirmed soybean rust had been found in Florida, Georgia and Alabama.
“When I heard Louisiana had confirmed soybean rust I thought, ‘Well, if they've got it chances are we do too,’” says David Wright, Extension agronomist at the North Florida Research and Education Center in Quincy.
The rust was found Nov. 15 by plant pathologists in a Group V research field on the Quincy station. Later, pathologists also searched kudzu — another host of the rust — living near the infected soybeans. Although not infected to the extent of the soybeans, they did find rust on the invasive species of vine.
Wright says infected soybean plants were found on row ends that deer had been grazing on. “Due to that, there was some regrowth and it was on those green leaves that we found the lesions. It was very important to have that regrowth, actually. Without it, all that we'd have had to look at were dried leaves on the ground.”
In Alabama, a suspicious soybean sample from a field in Mobile County tested positive for the rust.
At the same time, a county Extension agent in extreme southwest Georgia found the disease in soybeans nearing harvest. It was only the first of many suspicious samples pulled in the state.
“Our diagnostician suspects, based on samples brought in, that we've got this rust in a wide swath across the Coastal Plain,” says Bob Kemerait, Georgia Extension plant pathologist. “It appears to be wide-spread. In fact, in most places it was looked for, it was found.”
The rust hasn't been confirmed on Georgia kudzu yet. However, a sample from Seminole County looks “very likely” to be infected.
The big question Kemerait is being asked: How is Asian soybean rust being found in so many different scenarios and areas in the state so late in the year?
“The first thing, based on the where it, is we believe it came in on a hurricane. Second, we had numerous hurricanes and storms pounding us in a short time period. That kept us out of the field. When growers were able to get back in the field — and soybeans are a fairly minor crop for Georgia — it was time for picking peanuts and harvesting cotton. Third, soybean rust symptoms late in the year are almost exactly what growers were expecting to see from a healthy crop — drying down and defoliation. Had it been earlier, there would have been red flags and we'd have been more concerned.”
Arkansas was added to the list on Nov. 22 when a West Memphis-area soybean plant was confirmed to be hosting the disease. Following that initial confirmation, the disease has been found widely in the state.
“Most of (the infected) fields are along the eastern edge of the state. We've found suspect samples — not confirmed — as far north as Paragould (near the Missouri Bootheel) and as far south as Chicot County (bordering Louisiana),” says Rick Cartwright, Arkansas Extension plant pathologist.
The rust is being found on “old, late plants sitting out waiting for the frost to kill them,” says Cartwright. “Everyone needs to remember that after the first frost the rust will be over for Arkansas this year. It'll be killed back further south.”
The unfortunate thing with the disease is no one “has any idea what it will really do” in the Mid-South, says Chris Tingle, Arkansas Extension soybean specialist.