Rice yellow mottle virus

Causal agent and disease type. The disease is caused by Rice yellow mottle virus (RYMV), a member of the genus Sobemovirus. This is a severe viral disease that interferes with the physiological processes of the rice plant. The virus is highly persistent and can survive in the environment for extended periods.

Host range. The virus primarily infects cultivated rice (Oryza sativa). Other susceptible hosts include various wild rice species and certain grasses found in wetland ecosystems, which act as primary viral reservoirs during the off-season, facilitating the survival of the pathogen.

Symptoms and signs of infection. Initial symptoms manifest as mosaic patterns or yellow-green mottling on the leaves. As the infection progresses, leaves turn yellow or orange, the plant becomes stunted, and the panicles are often poorly developed or malformed. Severe infection frequently results in complete spikelet sterility.

Conditions for development and spread. The virus is transmitted mainly by insect vectors, particularly leaf-feeding beetles (Chrysomelidae). Transmission also occurs through mechanical contact, such as contaminated farm machinery or physical leaf-to-leaf contact between healthy and diseased plants in dense rice paddies.

Economic impact and disease management. RYMV causes significant yield losses, often ranging from 25% up to total crop failure. Effective management strategies involve planting resistant rice cultivars, rigorous weed control to remove virus reservoirs, practicing crop rotation, and implementing integrated pest management (IPM) to control insect vector populations.