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Asian soybean rust found in south Louisiana kudzu

LSU AgCenter specialists announced Asian soybean rust has been found in a Louisiana kudzu patch south of Lafayette near New Iberia. The disease has not been found in soybeans.

“Late yesterday afternoon, Blaine Viator reported he’d found something that looked a lot like ASR,” said David Lanclos, LSU AgCenter soybean specialist, shortly after the disease confirmation. “Along with several sentinel plots, Blaine has been monitoring that kudzu for a while. When he found this suspicious patch he gave us a call. He drove a sample to Baton Rouge this morning.”

After having a look, plant pathologists said Viator’s initial ASR diagnosis was correct.

Viator, a prominent sugarcane consultant in south-central Louisiana, found the infected kudzu in a low-lying area beneath a tree. That region has been receiving intermittent showers so there was moisture available to the disease.

“Our immediate plans include intensifying scouting efforts around the area,” said Lanclos. “I’ve been in regular contact with Blaine all afternoon. In fact, I spoke with him 30 minutes ago and he was in another sentinel plot. He’s been unable to find any more ASR. That’s very good news.”

Lanclos and colleagues are careful not to downplay the significance of the find. But as long as it’s hot and dry (conditions Louisiana is well familiar with this year), “it would be difficult for ASR to really get going. Even in that kudzu patch it hasn’t really spread. That goes to show where the sun is shining and there’s little moisture retention, the disease isn’t prevalent.

“The flip-side, of course, is if it does begin to rain and temperatures drop it would theoretically allow the disease cycle to pick up steam. Those conditions would certainly be optimum for it to get cranked up.”

Between 50 and 60 percent of the state’s soybeans are already at R-5.

“The cutoff for ASR, according to everything we know – and we are still on a learning curve – is once we get to R-6 there’s no real harm ASR can do to the crop. So we’re about two weeks away from being able to say 60 percent of our crop is safe.”

As for recommendations, “we’re not changing course just because of this kudzu patch. If it’s found in soybeans and appears to be spreading, then we’ll definitely change our tune.

“We’re not promoting not spraying. We’re just suggesting producers stay on the spraying program they’re normally on. If they’re not ones for any risk, they can add a triazole to the system. That might help some folks sleep better.”

The area the ASR was found in isn’t known for soybean production.

“It’s in the sugarcane belt. Traditionally, in a good year, between the parishes down there – St. Mary, Iberia and a couple of others – there’s around 30,000 acres of soybeans.”

And the area’s beans are some of the state’s earliest planted. Most producers there plant in early April and harvest in mid- to late August.

“This is unfortunate and I’m sorry ASR is back on farmers’ plates. But at this point, it’s not in beans and there’s no reason for panic. Everyone should keep looking for ASR and if it does spread, we’ll let everyone know immediately.”

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