What does the Asian soybean rust (ASR) look like?
The first symptoms usually appear as pinpoint-size lesions on the upper leaf surface of the lower leaves of the plant. These early lesions may first appear as yellow flecks and with age turn tan to brown or redbrown. The lesions may be angular or circular and may cluster near leaf veins. As the disease progresses, lesions may be numerous. Pustules form, mostly on the lower leaf surface on soybeans. These pustules erupt to release urediniospores through circular holes, which when examined with a hand lens, resemble microscopic volcanoes. The urediniospores may be powdery and tan or lightly pigmented. Lesions and pustules may also develop on petioles, stems, and pods. Chlorosis or mottling on leaves may also be associated with lesion development. As the soybean matures and sets pods, ASR spreads rapidly. Lesions can be found on petioles, pods, and stems, but are most abundant on leaves. Especially at the early stages, it is easy to confuse soybean rust symptoms with the symptoms of three
