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Reid Frederick, USDA Agricultural Research Service,

Australasian soybean rust

Phakopsora pachyrhizi

Australasian soybean rust (Phakopsora pachyrhizi) is a fungal pathogen of soybeans. It is a native of Asia, Africa and South America and was first detected in Louisiana in 2004.

The most common symptoms of infection by P. pachyrhizi are tan-to-dark brown or reddish brown lesions, usually clustered along the veins. As rust severity increases, premature defoliation and early maturation of plants is common. In areas where the pathogen commonly occurs, yield losses up to 80% have been reported.

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