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Deadly Katrina to move soybean rust spores to the MW and NE U.S., S. Ontario and Quebec
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By Marilyn Cummins, Editor
www.StopSoybeanRust.com
8/29/2005 4:45 p.m. CDT (updated 8/30 2 p.m.) – Deadly and devastating Katrina is far inland, continuing to spread heavy rains even as a weaker tropical depression. It roared up through Mississippi as a Category 1 hurricane late Monday, diminishing to a tropical storm then depression on its way to its recent location centered in Tennessee.
Soybean rust transport forecasts say the system will carry soybean rust spores as far west as southeast Missouri and as far north and east as Canada and the U.S. Northeast.
The storm made landfall on the northern Gulf Coast as a Category 4 hurricane early on Monday. New Orleans was spared from the direct hit so many had feared, but broken levees and rising waters are increasing the devastation and death toll. There is much devastation from winds, waves and rain there and at many points along the Gulf Coast. Biloxi and Gulfport, Miss., did take the full brunt of Katrina’s powerful winds and tides and Mobile, Ala., suffered tremendous flooding and major loss of life.
Katrina’s effect on soybean rust movement
The USDA Soybean Rust Forecast issued late today predicts new spore transport and depositions to follow in the path of Katrina and progressively move northeastward over the next three days.
The predicted area for Monday extended from the southeastern U.S. into eastern Texas, Arkansas, western Tennessee and Kentucky, and southern Indiana and Ohio. The predicted area for Tuesday spreads further west and north into southeastern Missouri, southern Illinois, Indiana, Ohio, southern Ontario, western New York and the western half of the Mid-Atlantic states. The predicted area for Wednesday extends further north and east into southern Ontario and Quebec, and all of the northeastern United States except for eastern Maine.
The USDA said that while spore transport is forecast to spread far north this week due to Katrina, it is important to remember that it typically takes several weeks of favorable disease weather for the development of infection after deposition.
Kentucky specialist spells out implications of Katrina’s pass through Kentucky
In his August 29 soybean rust update to his listserv members, Don Hershman, University of Kentucky Extension plant pathologist, gave the following prognosis for what Katrina’s journey north will mean to Kentucky soybean producers:
“Soybean rust (SBR) continues to be confined to the deep southern United States, primarily in southern AL, GA and FL. I feel confident in saying that there is no soybean rust in KY or anywhere near KY at this time.
“It is very likely that Hurricane Katrina will move spores of the soybean rust fungus into KY as it passes though in the next couple of days. What does this mean to KY soybean producers? Firstly, even though spores are likely to be brought into KY, the overall concentration of spores will be low and dilute. There simply is not enough acreage of soybean or kudzu affected by soybean rust in the Deep South to result in large numbers of spores blowing into any field in KY.
“As for the spores that do blow in, it will take 4-6 weeks before the disease will develop to the point where significant damage is possible, resulting from defoliation. That means if the present storm brings in a reasonable number of spores by mid-week, it will be at least the end of September or early October before any damage will be possible. By that time, most soybean fields in the state will be close to or at physiological maturity. In other words, soybean that will be near, at, or beyond physiological maturity by the end of September are home free (from soybean rust) for 2005.
“Fields that will not reach physiological maturity until mid-October or later are still at some risk to damage by rust. However, even in those cases, fields will not go from being clean to having a lot of soybean rust overnight. It will take a month or more.
“There will be plenty of time to react, should spraying be required, and there will be indications that the soybean rust risk is high, based on the disease being found close to, or even in KY. Spraying would only be advised in later soybean crops if soybean the soybean rust risk is high and there is still more than a month to go before the crop will be at the R6 stage. Fungicides should not be applied once a crop is at the R6 stage. In fact, most fungicide labels prohibit spraying soybeans that have reached the R6 stage.
“In my opinion, it is very unlikely that any more than a handful of Kentucky fields may need to be sprayed for soybean rust this year. It is highly possible that no fields will need to be sprayed. Overall, in my opinion, the prognosis is quite good that soybean rust will cause little or no damage to the 2005 Kentucky soybean crop.”
Sources: National Hurricane Center; USDA SBR Forecast for 8/29; an 8/29/2005 Kentucky rust listserv e-mail message from Don Hershman, University of Kentucky Extension plant pathologist; information from news wire reports.
For an easy way to stay informed, sign up for the weekly Bulletin e-mail newsletter from www.StopSoybeanRust.com. You also will receive our RUST FLASH e-mails alerting you to important breaking news as soon as it occurs. All are archived in Bulletins.
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