What does the Asian soybean rust look like?
The most common symptom of infection by P. pachyrhizi is tan-to-dark brown or reddish brown lesions. The disease begins with small, water-soaked lesions, which gradually increase in size, turning from gray to tan or brown. They assume a polygonal shape restricted by leaf veins and usually coalesce to form larger lesions. As the plant matures and sets pods, the symptoms spread rapidly to the middle and upper parts of the plant. Lesions are found on petioles, pods, and stems but are most abundant on leaves. Especially at the early stages, it is easy to confuse the symptoms of soybean rust with symptoms of three other soybean leaf diseases: brown spot, caused by the fungus Septoria glycines; bacterial pustule, caused by Xanthomonas axonopodis pv. glycines; and bacterial blight (also called angular leaf spot), caused by Pseudomonas savastanoi pv. glycinea.
