November 8, 2005

New Asian soybean rust found in US state
 

Georgia has reported a new county, Bulloch, as positive for Asian soybean rust (Phakopsora pachyrhizi) and has found a new type of plant that has fallen victim to the feared fungus.

One to two "pustules were found on one (soybean) leaf of 10 leaves collected," reported University of Georgia researcher Layla Sconyers via the USDA public rust website.

With 34 positive counties, Georgia has suffered the highest rust infection rate this season, followed by Alabama with 29, Florida with 23; South Carolina with 18; North Carolina with 13; Mississippi with two; and Louisiana with one.

University of Georgia extension soybean specialist Bob Kemerait said Friday that one Florida beggarweed plant was also found to be carrying rust in a field of infected soybeans in Decatur County, Georgia, last week, marking the first instance of the disease attacking any plant other than soybeans or kudzu in the continental US.

Florida beggar weed, often called 'dixie ticktrefoil', is a wild legume in the soybean family that grows across the Southeast, Caribbean and Gulf coast.

Computer aerobiological models utilised by USDA predict "very little soybean rust transport and depositions", to new areas of the Southeast through midweek, despite slightly favourable weather conditions.

Asian soybean rust is a major plant pest in Brazil, often requiring producers to apply fungicides four to six times in order to prevent severe yield losses. It was found for the first time in the continental US last November, sparking creation of a nationwide monitoring and diagnostic system this season.