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Dodging rust in Arkansas?

Some states to the east have gotten a taste of its badness. For Arkansas, though, the monster of Asian soybean rust is biding its time.

“Our beans are nearly done and, thankfully, rust hasn’t shown up,” said Rick Cartwright, Arkansas Extension plant pathologist. “Since it showed up last fall, we’ve had the time and support of the Arkansas Soybean Promotion Board to get ready. A lot of people, programs and equipment were placed. With the detection system we put in, we were extremely well-prepared for it. At least we think we were. It’s hard to say for sure without the disease showing up.”

During the growing season, Arkansas was “worked over” looking at plant samples. Because so much scouting was done for rust, “we learned a lot more about soybean plants early in the season and during flowering.

“Everything seemed to click,” said Cartwright, who spoke at the Rice Research and Extension Center field day in Stuttgart on Aug. 10. “That doesn’t mean we can’t miss the rust in the future but it helped us diffuse a lot of false alarms and rumors. Hopefully, it helped prevent some unnecessary fungicide applications — although some were made anyway.”

The Delta was helped by weather, wind patterns and the fact rust likely overwintered only in Florida. If soybean rust becomes established in Texas or Mexico, it’ll be more problematic for Arkansas. “If rust makes a home in Texas, it will be able to hit us from the left or right.

“I’m hoping people don’t say, ‘Well, it was a no-show. What’s the big deal?’ I agree with that sentiment to a certain degree. Soybean rust didn’t live up to its advertising.

“But I’ve been working around these plant diseases a long time. They’re very closely related to weather patterns. All it takes is a different weather pattern and we have the potential for a disaster.”

Cartwright has seen such scenarios play out in wheat and corn. In 2000, stripe rust started in wheat.

“It went through the wheat crop like fruit through a goose. We were scrambling to keep up on over 350,000 acres. Before we got ahead of it, the first fields stripe rust showed up in were 50 to 60 percent yield losses.”

Under favorable weather for a month to six weeks, soybean rust will make stripe rust “look like a sissy. We’ve got to keep that in the back of our minds. This state was hot and dry during April, May and June. The same conditions aren’t going to happen very often. Next year, if we have our normal weather during that period, all bets should be off.”

If factors converge with soybean rust, “there will be weeping and gnashing of teeth. This year, it didn’t happen. But the threat is still there — we have no resistance in our germ plasm.”

While the disease is manageable, Cartwright warned against underestimating its power based on this year alone.

“I am very, very happy we haven’t seen rust. But to me, on the disease discovery front alone, that fact is almost a worse headache. If we were in Brazil, we could say, ‘Well, by a certain date and growth stage, we have to spray. In a couple more weeks we’ll spray again and be done with it.’”

While that’s an expensive automatic input, strictly in terms of managing the disease, “it’s much easier.”

Unlike in South America, rust in the Delta will be much more complicated. “One year it’ll be a threat. The next two years it won’t be. The next year it could wipe out a bunch of fields. It’s a major unknown and makes dealing with it a huge challenge.”


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