Soybean Rust
Asian soybean rust, caused by the Phakopsora pachyrhizi fungus, is a major soybean disease that was discovered for the first time in the continental United States in nine southeastern/Midwestern states in November and December 2004. First detected in Japan in 1902, Asian soybean rust can cause premature defoliation, with yield losses of up to 70% reported in farms in Asia. The main effects on the soybean plant are destruction of photosynthetic tissue, which in turn causes premature defoliation, early maturation, and severe yield reductions through reduction in the number of pods and seeds, and decreased seed weight.
Scouting for soybean rust may begin at anytime during the growing season, but detection is typically easiest just prior to or during the flowering stages. Infection usually begins on leaves low in the canopy, and chlorotic regions begin to appear along with lesions found mainly on the lower leaf surface, although they can appear anywhere on the plant. Symptoms and signs will move to the middle and upper plant canopy as the severity of the infection increases.
Signs of infection include tan or reddish lesions containing raised uredinia postules, mainly on the underside of leaves. Areas surrounding reddish lesions may be necrotic. Uredinia may also be found on upper leaf surfaces, though they are typically smaller and less abundant. Lesions are restricted by leaf veins, and may be as large as 2-3 square millimeters.
The links below provide information and guidance on soybean rust:
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