Rice ragged stunt

Rice ragged stunt is a destructive viral disease caused by the Rice ragged stunt virus (RRSV), a member of the Oryzavirus genus within the Reoviridae family. This pathogen specifically targets Oryza sativa, causing severe stunting and reproductive failure, which often results in significant yield losses in affected rice-growing regions.

The virus is transmitted in a persistent manner by the brown planthopper, Nilaparvata lugens. Once a hopper feeds on an infected plant, the virus undergoes a latent period within the insect's body. After this period, the vector remains infectious for the remainder of its lifespan, facilitating the spread of the virus across rice fields as the insects migrate and feed.

Symptoms of the disease are highly diagnostic and include intense plant stunting, which gives the crop a dwarf-like appearance. Leaves often exhibit ragged, twisted margins, and small galls or vein swellings may develop on the leaf blades and sheaths. These physiological disruptions lead to delayed panicle emergence and often result in sterile grains, drastically reducing the overall harvest.

Development and spread are heavily influenced by the population density of the brown planthopper and environmental conditions favoring its breeding, such as warm temperatures and high humidity. Inefficient farm management practices, such as continuous cropping or lack of fallow periods, provide a constant supply of host plants, allowing the virus to persist and thrive throughout the growing season.

Control measures are essential to mitigate the impact of this viral disease:

• Deploying resistant rice varieties to prevent infection and limit vector feeding.
• Implementing integrated pest management (IPM) to maintain brown planthopper populations below economic thresholds.
• Utilizing synchronous planting strategies to reduce the period of available host material.
• Removing volunteer rice plants and alternative weed hosts that act as virus reservoirs during the off-season.