Symptoms and Signs
Symptoms of cucumber mosaic in common beans vary considerably depending on the variety and strain of the virus. Severe symptoms may include dark green blisters and vein banding, interveinal yellowing and leaf distortion that may resemble damage due to the herbicide 2,4-D. Milder symptoms may include a light-green to dark-green mottle and some green vein banding. Symptoms can be confused with those caused by Bean yellow mosaic virus and Bean common mosaic viruses (see photo comparison).
Comments on the Disease
Cucumber mosaic is not a very common disease on beans. Although it has a very wide host range and infects many crops, ornamental plants, and weeds, only certain strains of Cucumber mosaic virus infect common beans. These same strains also infect alfalfa, peas, pepper, lima bean, and blackeyes. Cucumber mosaic virus can be seedborne in bean as well as transmitted by aphids. It can overwinter in perennial crops and weed hosts.
Currently there are no effective control measures for cucumber mosaic disease in beans. The use of certified disease-free seed may help minimize the incidence of seedborne cucumber mosaic. Avoid growing beans adjacent to alfalfa fields or established pepper fields. There are no resistant varieties, although some varieties are more tolerant than others.