soybeans rust diseases

ALABAMA EXTENSION SPECIALISTS are advising soybean growers in the northern region of the state to be prepared to make fungicide applications for soybean rust, as it has been detected in several locations. Shown inspecting a field during a recent informational meeting held in Blount County is Extension Plant Pathologist Ed Sikora.

Soybean rust showing up a month early in north Alabama

Soybean rust has been found about a month earlier than normal in north Alabama. Growers are being advised to make fungicide applications where needed to protect yield potential.

Soybean rust has been discovered about a month earlier than normal in north Alabama, and growers there are being advised to make fungicide applications where needed to protect their yield potential.

“Rust has been found on the Tennessee Valley Substation at Belle Mina,” said Charlie Burmester, agronomist with the Alabama Cooperative Extension System. “It’s about a month earlier than we’ve seen it up here before, but there’s no reason to panic about the situation. We’re just trying to get information out to growers so they’ll know what to expect.”

Burmester and other Extension specialists discussed the current situation with growers during meetings this week in Blount and Limestone counties.

Extension plant pathologist Ed Sikora confirmed sightings of soybean rust in north Alabama. “The rest of the country looks at soybean rust as a Southern problem, and I suspect most of you have looked at it as more of a south Alabama problem over the past few years. It really hasn’t made its way up to the northern third of the state until late August or early September,” he says.

It can be a devastating disease, Sikora told growers at a meeting on Jimmy Miller’s farm in northeast Alabama’s Blount County.

“In some of our disease plots last year, we saw soybean yield decreases of up to 40 percent in unsprayed situations. Some growers got hammered last year. They decided it wasn’t a problem and they failed to spray. Instead of 50 to 60 bushels per acre, they were getting 25 to 30 bushels. They still made a good crop, but it could have been a lot better if they had sprayed,” he says.

Soybean sentinel plots are in Crossville, Belle Mina and about 18 other locations in Alabama, says Sikora. “In Crossville, about two weeks ago, we found low levels of soybean rust — about two plants out of 1,000 that I surveyed. In the same week, samples were collected from our Belle Mina plot, and we also confirmed soybean rust there. This is about a month earlier than we’ve ever detected it in this area.”

The disease has been found very early in its cycle, giving growers time to prepare for it, he says. “It’s nothing to panic about. It’s a disease that easily can be controlled with fungicides if they’re applied in an effective and timely manner. We have time to deal with this problem.”

Other disease problems are also being found in the region, he says, including frogeye leaf spot and downy mildew.

“Frogeye also looks as though it’s coming in earlier this year, and it can be more devastating than soybean rust if it gets started early. I’m most concerned about frogeye leaf spot and soybean rust.”

Sikora says he expects most fields in northeast Alabama have been exposed to soybean rust. “When we start seeing symptoms on the plant as we did, it means the disease blew in two to three weeks earlier, so we’re in the early stages.”

Early planted soybeans should be okay, he says. “In fields where we at the R3 or R4 stage, I think one fungicide application with a triazole-type fungicide would be very effective in keeping down rust and helping with frogeye, especially if soybeans haven’t been sprayed previously. I’m mostly concerned with late-planted soybeans. Some were planted just last week, and I’m amazed at the growth stage already. If the moisture continues and these beans develop quickly, we may have to spray earlier with fungicides than we have sprayed in the past.”

On late soybeans, Sikora recommends spraying at the R2 or R3 stage. “This is a whole new situation for us, and we’ve never seen rust before at the R3 stage. I would probably wait until full bloom or early R3 before I started a spray program. You could go with a tank-mix at R2 or R3, and three or four weeks later – depending on the product you’re using – go in with a triazole by itself.”

Conditions right now are not favorable for rust to build quickly, but with the excessive moisture the region has received this year, it’s difficult to predict what the disease will do, says Sikora.

“Don’t get caught behind the eight-ball. We’ve got good information early, so be aware of it, and be ready to spray as the season progresses, especially with all of these late soybeans. There’s a tremendous amount of inoculum in the Southeast, and if we have storms moving up later, it could pose a tremendous problem.”

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