Early symptoms of rust appear as small lesions on the leaves that become brown to reddish brown and may be confused with bacterial pustule. Under closer examination, tiny bumps within the lesions can be observed. The bumps are spot structures called uredia, which give the leaf a rusty look. Uredia are primarily found on the underside of the leaf, with fewer and smaller uredia forming on the top of the leaf.Rust-infected leaves eventually turn yellow and fall off the plant. Premature defoliation and a reduction in the number of days to maturity will cause infected plants to have lower seed weight and fewer pods and seeds. Different soybean varieties may have slightly different reactions to the disease. Also, the disease can appear very similar to other diseases that can affect beans.In areas heavily infected with rust, farmers walking through their fields have observed clouds of spores floating in the air.