Florida and Mississippi: Two new Asian rust sites identified

For the first time, Asian soybean rust has been found in a commercial soybean field in Florida. For the second time, it's been found in a Mississippi sentinel plot.

The Florida discovery is in Hamilton County, on the north-central border with Georgia. “The rust isn't severe at all — from the central infection, the rust might have branched out a foot or two,” said David Wright, Florida Extension soybean specialist.

“The soybean field it was found in was chest-high and bushy. The beans were Group 5s in the R-1/R-2 stage, planted mid-May. My understanding is a scout with the Florida Division of Plant Industry found it. They've had scouts out looking for rust in beans and kudzu.”

Lately, Florida growing conditions have been excellent. Since the field's canopy was so dense, “air wasn't moving through the crop very well. That's one reason infection was able to get going.”

Patches of rust have now been found across the Florida panhandle and Wright believes current weather conditions — daily showers and warm temperatures — will lead to even more. “It wouldn't surprise me at all to find more rust over the next week or so. We're set up for more infection.”

For that reason, “we're recommending soybean producers in the early bloom stage use a fungicide with curative effects. If weather conditions remain this damp, another application may be needed in a couple of weeks.”

The latest incidence of rust in Mississippi was in a Poplarville-area sentinel plot sponsored by the Mississippi Soybean Promotion Board. The infection level on the Group 5s is “less than half of 1 percent,” said Alan Blaine, Mississippi Extension soybean specialist.

Even so, “we're telling farmers south of I-20 if they haven't already made a fungicide application, they need to give one serious consideration. Rust appears to be spreading a little. However, we still don't feel the inoculum is built up as much here as it appears to have in the Southeast. And prevailing winds look to be helping us.”

Following a precedent established with the infected George County plot in mid-July, the Poplarville plot “is being destroyed as we speak,” said Billy Moore, Mississippi Extension plant pathologist. “To keep any spores from getting to commercial fields that's the approach we're taking.”

Moore, the discoverer of both Mississippi rust occurrences, said the rust's movement remains sluggish. “I still feel we're in good shape. The inoculum level remains very low.

“Yesterday afternoon, after finding it in the sentinel plot, we went to a 140-acre bean field about 7 miles away. We also checked fields in Wayne County — about 50 miles from the original find in the Lucedale sentinel plot. We could find nothing suspicious.

“Today, we just finished checking fields right on the Mississippi/Louisiana line. We've found nothing in that area either.”

Next, Moore and colleagues will “have an intensive look at producer fields around Hazelhurst.”

Anyone who decides to use a fungicide “needs to be certain of what they're using and why they're using it,” said Blaine. “If you're south of I-20 and haven't made an application, go ahead and make one. But we're not recommending anyone come back with a second application yet. We just don't have the rust load to concern me enough to recommend that.”

The particulars of an application are different for every grower: the crop stage, the timing, the product and everything else must be considered. “We're happy to work with anyone on those considerations,” said Blaine. “Just give us a call. And prior to making a fungicide application, check your insects. See if there are some pest populations you're dealing with. If you are, a tank-mix may be in order.”

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