Arkansas added to Asian soybean rust list

Add Arkansas to the growing list of states harboring Asian soybean rust. On Thursday, a suspect plant was located in Crittenden County in the northeast corner of the state. The sample was sent to the USDA lab in Beltsville, Md., which confirmed the disease today.

“We’ve been monitoring our fields ever since the discovery in Louisiana,” says Rick Cartwright, Arkansas Extension plant pathologist. “But until Nov. 18, we hadn’t found any clear-cut samples. Eventually, we found it in the West Memphis area – a little further north than we anticipated.”

Following initial confirmation on the West Memphis plant, the disease has been found widely.

“We fanned out and found a number of fields with suspected rust. Most of those 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).”

The first Arkansas rust sample was discovered by a member of the Arkansas Working Group on Introduced Plant Diseases – recently set up for just such a purpose. Chris Tingle, Arkansas Extension soybean specialist, says the group has functioned, “like clockwork.

“Fortunately the rust wasn’t detected in Arkansas first. That allowed us to be proactive instead of defensive in our response. We’ve had plans in place for at least nine months to deal with this eventuality. Those plans went off without a hitch.” (Asian soybean rust findings have now been confirmed in Alabama, Florida, Georgia, Louisiana and Mississippi.)

“The truth is, (before the West Memphis discovery) we had other samples pulled that we thought were possibly rust,” says Cartwright. “They weren’t suspicious enough to send on to the (Beltsville) lab. This sample from Crittenden County was plenty suspicious, though, so we sent it on.”

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 Tingle. “We’re basing our decisions on what’s been seen in South America. It could turn out to be much worse than what they have there. Then again, it could be a very minor disease for us. We just don’t know. This is the beginning of our information gathering.”

To aid that effort, Tingle says Extension personnel across the Mid-South are in close contact. There are already joint meetings and conference calls lined up, “so we can all work in unity. That will allow the latest information from the Mid-South to reach all the growers as soon as possible.”

While finding the rust so far north was initially surprising, Tingle says his surprise diminished when he considered shifting soybean systems in the state.

“When we got the word on rust in Louisiana, I immediately contacted agents in southeastern Arkansas. You know, ‘Let’s get out and make sure we’re clear.’

“They didn’t find anything. But we’ve seen a tremendous push in that area towards an early planted system. So the crop in the southeast was mostly out of the field by Mid-September. That meant fewer chances to find (rust) there. On the flip side, as you move north, there are more opportunities for the disease to be expressed late. If you think in those terms, it isn’t so shocking that the rust was found further north first.”

Cartwright maintains his belief the disease arrived via Hurricane Ivan in September. “It just brushed the eastern edge of Arkansas and, apparently, that was enough to dump spores on us.”

Besides soybeans, Cartwright and colleagues have also been monitoring kudzu. So far, they haven’t found soybean rust on the vine.

“The disease overwintering on our kudzu isn’t a concern – again, the first frost will take care of it,” says Cartwright. “But the working group wants to have a map of where the disease has been found so we’re checking.”

At this point, Tingle insists there’s no reason for major worry. “There’s no question that this country has the most information and preparation for a plant disease than anything I’ve ever been involved with. We’re ready for this.”

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