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Asian soybean rust confirmed in Alabama sentinel plots

BALDWIN COUNTY, Ala. - Asian soybean rust has been confirmed in several southern Alabama sentinel plots, according to Extension specialists with Auburn University.

“A graduate student found Asian soybean rust on Tuesday afternoon in sentinel plots around Fair Hope, Ala.,” said Ed Sikora, Extension plant pathologist with Auburn. “That’s in Baldwin County, across the bay from Mobile.”

Rust was found on two plants with “roughly 10 leaves on each plant showing symptoms in the lower canopy – typical lesion formations. The samples were brought to Auburn yesterday. We confirmed the rust through several tests.”

Two sentinel plots were planted in the area – one late; one earlier. “One of the infected plants was found in the older sentinel plot where beans were at R-6. The other plant was found on the neighboring sentinel plot at R-1/R-2.

“We also have Syngenta spore traps – slides covered with petroleum jelly – in the area,” said Sikora. “On Monday, we found four spores that look like Asian rust spores in one of those traps.”

Sikora is advising producers in south and south-central Alabama to “strongly consider a tank-mix or a pre-mix of a triazole and strobilurin. We just don’t know how far it’s moved up.”

There’s no indication rust has spread in neighboring Georgia. Rust was found on volunteer soybeans in the extreme southwest part of the state two months ago. Thus far, it seems to be staying put.

“Our scout team has spent yesterday and today scouting our sentinel plots,” said Phil Jost, Georgia Extension soybean specialist on Thursday afternoon. “Up until 3 p.m. today, we haven’t found anything to worry about. The only soybean rust we’ve found remains in Seminole County on volunteer beans. I hope that remains the case.”

Conditions in Georgia have been conducive to soybean rust over the last week of June.

“If you wanted ideal conditions for rust to take off, Georgia has had them lately,” said Jost. “We’ve been very rainy and humid, especially on the eastern side of the state. Thankfully, so far, no rust is showing up.”

In neighboring Mississippi, Extension soybean specialist Alan Blaine said most of the state’s crop is at a stage where “we normally spray a fungicide for things other than Asian soybean rust. The decision for producers is whether to spray a (triazole/strobilurin) as well. At this point, I don’t think we have (Asian rust).”

Blaine’s belief is bolstered by two factors: weather and scouting.

“You have to consider where the rust was found in Alabama. They found it north of Gulf Shores on the coast – it rains there frequently. I can assure you we haven’t had rain frequently in the soybean-growing areas of Mississippi. Based on that, I’m not going to change my plans for our test fields yet. Even if it is spreading, it doesn’t appear there’s a whole lot of innoculum out there.”

Currently, an Extension crew is in south Mississippi looking for rust.

“Since yesterday afternoon, they’ve checked soybeans around Jackson, Ala., and in Mississippi they’ve been all around Lucedale, Poplarville, and Tylertown,” said Blaine. “We’re on the way to check fields in Meadville and Natchez now. We’ll be in the Delta scouting tomorrow. As of 11 a.m. today, we haven’t found anything suspicious.”


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