Common diseases of soybean are caused by viruses, bacteria, fungi and nematodes. Some diseases are spread by insect vectors and nematodes while others are spread by wind, splashing rain, or movement in soil. The best way to determine if disease control would be profitable is to first identify the diseases that are capable of causing  conomic yield losses. Symptoms of disease include plant damage caused by a pathogen and the reaction of plants to infection. Signs are the visible evidence of the pathogen. Some diseases have characteristic symptoms and signs that are identifiable in the field.