Mungbean yellow mosaic

Mungbean yellow mosaic is a devastating viral disease caused by members of the Begomovirus genus, within the Geminiviridae family. It is a systemic viral infection that disrupts the photosynthetic apparatus and physiological balance of susceptible host plants. The disease is recognized as one of the most severe constraints to the production of grain legumes in affected regions.

The host range of the virus includes a wide variety of legumes, most notably mungbean, soybean, black gram, and common bean. The virus also relies on various weed species that serve as alternate hosts, allowing the pathogen to persist in the ecosystem throughout the year, even when the primary host crops are not present.

Symptoms typically manifest as small, chlorotic spots or streaks on young leaves. These spots gradually enlarge and coalesce, resulting in a yellow mosaic pattern that eventually covers the entire leaf area. Severe infections can lead to leaf curling, stunting of the plant, and significant floral abortion, which drastically limits pod and seed development.

The virus is transmitted exclusively by the whitefly Bemisia tabaci. The spread of the disease is highly correlated with the density of whitefly populations in the field. Warm temperatures and arid conditions are conducive to rapid multiplication of the vector, leading to quick secondary spread of the virus throughout the crop canopy. The virus cannot be transmitted through mechanical contact or seeds.

Management strategies focus heavily on integrated pest management (IPM) to control the whitefly population:

• Deploying resistant or tolerant cultivars as the primary defensive measure.
• Implementing sticky traps and monitoring the vector population closely.
• Applying systemic insecticides to minimize vector feeding and transmission.
• Removing weed hosts from the field margins to reduce initial inoculum.
• Adjusting planting dates to minimize exposure during periods of peak whitefly activity.

The economic impact of Mungbean yellow mosaic is profound, with yield losses often ranging from 50% to 100% depending on the stage of crop development at the time of infection. Early-season infections are particularly destructive, often rendering the crop economically non-viable and requiring emergency management interventions to save the remaining stand.