Pest of the Month -- June

Soybean Rust

The Asian soybean rust, Phakopsora pachyrhizi, is one of the most devastating foliar diseases of soybean. In Asia and Australia, yield losses up to 80% have been reported. In 2004, Asian soybean rust was confirmed for the first time in Louisiana, Mississippi, Florida, Georgia, Alabama, Arkansas, Missouri, South Carolina, and Tennessee.

All current commercial soybean varieties are highly susceptible to this disease. The most common symptoms on cultivated soybean are small light-colored, irregularly shaped spots (lesions), which turn brown or reddish as the disease progresses (see inset). Soybean rust causes premature defoliation leading to crop losses, fewer seeds and pods, and early maturity. Airborne spores readily carry this disease from field to field and if spores enter the jet stream, they can be transported very long distances. That Phakopsora pachyrhizi infects over 95 species of plants, including kudzu, makes it likely that this pathogen can survive and overwinter in the southern U.S. -sources: Miles, et al., 2003Soybean Rust: Is the U.S. Soybean Crop At Risk? ASPnet Feature June 2003; Southern Plant Diagnostic Network (http://spdn.ifas.ufl.edu/soybean_rust.htm)

Joe Hennen, Botanical Research Institute, www.invasive.org