March 16, 2005


Moderate risk of Asian soy rust spreading in the US



Current weather patterns pose a moderate risk of spreading soybean rust spores to fresh areas of the southeastern US, according to forecasts issued late Monday by the North American Plant Disease Forecast Center at North Carolina State University.


The extension center - selected as the official government forecasting unit for the yield-killing fungus in 2005 - said although overcast skies, rain showers and temperatures in the 70s Fahrenheit Monday produced conditions "favorable for disease development near the source" of 2005's original infection, "transport to other areas is unlikely" due to steady offshore winds.


Exposure to several hours of direct sunlight kills airborne spores. Cloud cover shields airborne spores and allows them to survive.


Thus far, the devastating fungus has only been found at one location in the continental US, over wintering on kudzu plants growing in Pascoe County, Florida.


Onshore winds are expected to increase the chance of spore dispersal on Tuesday and early Wednesday, creating "moderate risk to susceptible plants in central and northern Florida and southeast Georgia," said the center. The center defines moderate risk as a 40-60 percent chance of spreading.


Since the original 2005 discovery Feb. 23, the center said spore dispersal has primarily been limited to adjacent areas of Florida, plus coastal regions of Georgia and the Carolinas. The agency releases rust forecasts three times weekly - on Monday, Wednesday and Friday afternoons.


Crop Insurance Deadline


Should Asian soybean rust become a problem this year, many farmers will protect their harvest with crop insurance as well as fungicides, although Tuesday is the deadline for purchasing policies on spring-planted crops in the Midwest and central to northern Plains.


Crop insurance can cover economic losses caused by soybean rust, said Purdue University agricultural economist George Patrick.


"Soybean rust, if it occurs naturally, would be an insured peril," Patrick said. "If a farmer has a crop loss which exceeds the insurance deductible and is caused by rust, they're covered by the insurance."


But like other disease, insect and weed threats, crop insurance will only cover yield losses related to soybean rust if a farmer has made a reasonable attempt to stop the pest, Patrick said.


"A farmer has to use what they call good farming practices;" he said. "If there were a rust outbreak, the farmer would be expected to try to control it. They'd have to spray fungicide, put it on in a timely manner and in adequate quantity."


Crop insurance premiums are actually lower in many areas this season, despite the increased threat to production posed by soybean rust.


Consequently, insuring soybeans against rust could be a bargain, at least for the coming season, Patrick said. Since soybean rust is new to the US, "the premium rate does not reflect the added risk of the rust that we may be facing," he said.




Louisiana uncovered the first-ever case of soybean rust in the mainland US last November, followed by discoveries in eight other states, some as far north as the Missouri Bootheel.


Experts believe hurricanes carried rust into the US from infected areas of South America and the Caribbean last summer. Rust spores can travel up to 300 miles per day, under favorable atmospheric conditions.


The American Phytopathological Society said in general, conditions that promote good growth and full canopy development of the soybean crop are also the conditions most suitable for development of soybean rust, including temperatures in the range of 59-82 degrees Fahrenheit, with 68-75 degrees ideal, and a minimum of six to 12 hours of continuous moisture, such as rain or dew.


Asian soybean rust, Phakopsora pachyrhizi, has been known to quickly reduce soybean yields by 80-90 percent in infected areas of Asia, Africa and South America. There are no soybean varieties known to be resistant to the fungus, originally discovered over a century ago in Japan.


A risk assessment conducted by Iowa State University plant pathologist X. B. Yang indicated soybean rust could conservatively produce, "yield losses greater than 10 percent in nearly all the US soybean growing areas, with losses up to 50 percent in the Mississippi delta and southeastern coastal states."


The US Department of Agriculture estimates economic losses to producers could range from $640 million to $1.3 billion this season, and up to $2 billion in each subsequent year, depending on the severity and extent of rust.


An analysis undertaken by USDA's Animal Plant health Inspection Service found that - assuming normal climactic conditions - all areas of the US soybean belt stand at least a 50 percent chance of contracting soybean rust annually, with that risk roughly rising to 70-100 percent for fields lying east of the Mississippi River.


A poll conducted by agriculture chemical firm United Phosphorus Inc. at the recent Commodity Classic farm convention in Austin, Texas, found 45 percent of all soybean growers feel Asian soybean rust is their top crop-protection concern for 2005.

Video >

Follow Us