Bean yellow mosaic virus

Bean yellow mosaic virus (BYMV) is a significant plant pathogen classified within the genus Potyvirus of the family Potyviridae. It is a filamentous, single-stranded RNA virus that causes systemic infections in various legume crops, including common beans, peas, lupins, and broad beans, as well as several ornamental plants.

Symptoms usually include a distinct yellow mosaic pattern on the leaves, vein clearing, leaf deformation, and stunted growth. The severity of the symptoms depends on the host cultivar and the timing of the infection. Plants infected early in the season often show severe yield reduction and poor seed quality, making the crop commercially unviable in severe cases.

The biological cycle of BYMV is dependent on aphid vectors. The virus is transmitted in a non-persistent, stylet-borne manner. This means that aphids can pick up the virus from an infected plant and immediately transfer it to a healthy host without the virus needing to circulate within the insect. The pathogen overwinters in perennial legumes, which act as primary inoculum reservoirs.

Environmental factors such as high aphid activity, warm temperatures, and proximity to infected perennial weeds or pastures facilitate the rapid spread of the virus. Because the virus is non-persistent, its transmission is extremely fast, making it difficult to control through insecticides alone if the aphid population is dense and active during the susceptible growth stages of the plant.

Control strategies for BYMV focus on reducing the primary source of infection and limiting the spread by vectors. Effective measures include planting certified virus-free seeds, maintaining a spatial buffer between sensitive crops and perennial legumes, and monitoring aphid populations. Breeding and cultivation of resistant or tolerant cultivars remain the most effective and sustainable long-term solution.

• Monitoring for aphid infestation early in the season.
• Maintaining field sanitation and weed control.
• Implementing spatial separation from perennial legumes.
• Selecting resistant or tolerant legume varieties.