Wissadula yellow mosaic virus

Pathogen and disease type. Wissadula yellow mosaic virus (WiYMV) is a viral plant pathogen classified within the genus Begomovirus, family Geminiviridae. The virus consists of a circular single-stranded DNA genome. It is a strictly vector-borne disease, relying entirely on the whitefly Bemisia tabaci for its transmission between plants, and it is not transmitted mechanically or through seeds.

Affected crops. Originally identified on wild weeds of the genus Wissadula (family Malvaceae), the virus has a significant impact on economically important agricultural crops within the same family. Cotton and okra are particularly susceptible to infection. The presence of these reservoirs near cultivated fields significantly increases the risk of virus outbreaks in agricultural regions.

Symptoms and signs. The characteristic sign of the infection is the development of a distinct yellow mosaic pattern on the leaves, manifesting as bright yellow or pale green patches. Infected plants often show stunting, leaf curling, and severe distortion of leaf margins. These symptoms interfere with photosynthesis and development, leading to a noticeable reduction in the plant's overall vitality and eventual yield capacity.

Development and damage. Disease prevalence is closely linked to the population dynamics of the whitefly vector. Favorable weather conditions, such as high temperatures and relative humidity, accelerate the life cycle of the vector, leading to rapid spread throughout the field. The virus causes significant economic damage, primarily through reduced fruit size, low quality of the produce, and overall growth failure of infected crops.

Protection and prevention measures. Since there is no curative treatment for infected plants, disease management focuses on prevention and vector control:

• Implementing integrated pest management (IPM) to control whitefly populations.
• Sanitation practices, including the eradication of Wissadula weed species near cultivated crops.
• Utilizing cultural practices like crop rotation and maintaining clean field borders.
• Monitoring the health of incoming transplants and ensuring the use of certified virus-free seeds where applicable.