White leaf spot

White leaf spot is a fungal disease caused by the pathogen Phaeoramularia manihotis (formerly known as Cercospora manihotis). This disease specifically affects plants like cassava, causing severe damage to the foliage and impacting the overall plant health.

Symptoms of the infection manifest as distinct, angular spots on the leaves. As the disease progresses, these spots turn white or light gray, often surrounded by a darker border. Under conditions of high humidity, the underside of the leaf shows signs of fungal sporulation, which appears as a grayish, downy growth of conidia.

Development and spread of the pathogen are highly favored by wet and humid environmental conditions. The fungus produces spores that are easily disseminated by wind currents, rain splash, and movement within the canopy. Poor air circulation and overcrowding of plants are key factors that accelerate the spread of the infection.

The economic impact of this disease is primarily seen in the premature senescence and shedding of leaves. Since photosynthesis is directly impacted by the loss of foliage, the plant's ability to store starch in its roots is drastically reduced. In cases of severe infection, farmers may face significant reductions in crop yields and root quality.

Management strategies for controlling White leaf spot involve an integrated approach. The most effective methods include the cultivation of resistant plant varieties, practicing crop rotation, and maintaining proper spacing to ensure adequate airflow. Sanitizing the field by removing infected plant debris helps reduce the primary inoculum for the next season, while targeted fungicide applications can be used if necessary.