The roots appear dark, and dark markings to appear on the lower stem and the petioles. On some varieties, a net-like browning of the veins occurs on the leaves. This disease is spread from plant to plant by at least 12 aphid species. Many of these feed on alfalfa, clover, and rye. It has been noticed that beans planted near these crops tend to have Common mosaic worse than those in other fields.
Transmission is in a non-persistant manner.
This means that the aphids acquire the virus almost immediately from infected plants, but are able to transmit it to healthy plants for only a few days to a week. This virus can survive in seed for more than 30 years, and can survive heat treatments hot enought to kill the seed. Do not plant beans near alfalfa, clover, and rye. Resistance is available, and is the most effctive way to control this disease. See current recommendations for aphid control.