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ALERT: Soybean rust found in AL soybean sentinel plot
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By Marilyn Cummins, Editor
StopSoybeanRust.com
6/30/2006 (Corrected version) 4:45 p.m. CDT -- Asian soybean rust has been confirmed in the Baldwin County soybean sentinel plot at Fairhope, Ala. [Our earlier report that AL officials recommend spraying was not correct. GA officials did say SW GA growers should get ready to spray at bloom. The following article replaces the AL information from this morning's version.]
According to the Alabama state commentary from 6/29/2006 on www.sbrusa.net, "soybean rust was confirmed on soybeans in Alabama yesterday. This is the second report of soybean rust on soybeans in the United States in 2006."
[Editor's note -- while the first report on soybeans this growing season was in a Florida sentinel plot 6/15/2006, rust also was found on late-harvested 2005 soybeans in Texas in February 2006.]
"The disease was detected on leaves collected from the Baldwin County soybean sentinel plot in Fairhope on June 27. The leaves were incubated for 48 hours, and we observed the pustules and spores typical of this pathogen. A total of five soybean rust lesions were observed on three leaves.
"The disease was detected on Pioneer 93M90 (maturity group III) at the R5-R6 growth stage. The disease was not observed on a maturity group IV variety (Pioneer 94M80) at the R4 growth stage planted adjacent to the 93M90's.
"Leaves were also collected from three commercial soybean fields in Baldwin County but no rust was observed. These fields ranged in development from V4-V6.
"Also on June 27, leaves were collected from a kudzu patch in Daphne, Ala., which is also in Baldwin County. This patch was previously reported to be infected with soybean rust on February 15. After incubation, we only observed one leaf with rust pustules but with no spore development.
"Leaves were also collected and incubated from a previously infected kudzu patch in the town of Chickasaw near downtown Mobile in Mobile County. We only observed one leaf with actively sporulating pustules from this patch."
Alabama rust scouting and management guidelines
[These were last updated on the AL commentary 4/17/2006]
"It is not considered economical to apply fungicides for soybean rust prior to bloom. Be aware of soybean rust alerts for your area to determine if rust is a threat. Call the Auburn University Soybean Rust Hotline for weekly updates at 1-800-446-0388.
"Soybean fields should be scouted weekly for soybean rust. Symptoms will appear first on the lower leaves in the canopy, so when scouting, push back the mid and upper canopy leaves to view the lowest leaves on the plant. Symptoms can appear along field borders (shaded areas) or out in the middle of a field depending on how spores were deposited. The first symptoms of rust are very small brown to brick red spots in a non-descript yellow spot on the upper leaf surface. Eventually, slightly raised pustules form in the spots, primarily on the lower leaf surface. As pustules become numerous, leaves turn yellow and drop prematurely."
Georgia recommendations after 6/29/2006 Alabama find
In today's state commentary, Georgia soybean rust coordinator Bob Kemerait of the University of Georgia posted the following:
"The report today of soybean rust in sentinel plots in lower Alabama is significant for soybean growers in Georgia, as Fairhope is not too far from the southwest corner of our state. Although we have found soybean rust on kudzu recently in Miller and Brooks County, we have not yet found it on soybean in Georgia.
"If rust is active in Baldwin County, Alabama, it is very likely to spread to soybeans in southwestern Georgia as well.
"Our current recommendations for soybean growers in Georgia are as follows:
Southwest GA:
"Soybean growers in the southwest corner of the state, e.g. Seminole, Decatur, Early, Mitchell, Backer, etc., should plan to make their first fungicide application to protect against rust as their crop enters the bloom stages.
"For more information on fungicides to apply at this timing, refer back to our Soybean Newsletter and Soybean Production Guide, or contact us.
Elsewhere in GA:
"Growers elsewhere in Georgia should follow the spread of rust in Alabama and especially in Georgia and anticipate that they will need to spray their crop at some time in the future as the disease spreads into our sentinel plots."
Kentucky specialist says AL find signals shift in rust situation
Don Hershman, University of Kentucky plant pathologist, notes that this find was made almost to the day when it was found in Baldwin County (Fairhope) last year.
"One big difference, according to Ed Sikora, is that Fairhope is down
15 inches in rain compared to last year, and the beans are very drought stressed," Hershman said. "This indicates to me that the soybean rust pathogen is able to infect (albeit not at high levels) even under very dry conditions.
"This find is significant in that I believe it signifies a shift in the soybean-rust situation for this year. I anticipate we will now begin to see an upturn in soybean rust. The main question now is how fast it moves and where.
"At this point, it is a race against time as far as the soybean crop goes. Most of our full season soybeans are nearing or are in the reproductive stages. Doublecrop soybean are considerably further behind in development," he said.
Hershman said that because he believes things will begin heating up soon, he will begin making daily updates on the KY soybean rust hotline beginning on Monday, July 3. The number is 1-888-321-6771, with his recommendations archived online.
Source: Alabama and Georgia state commentaries on www.sbrusa.net; Don Hershman listserv e-mail.
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