Passalora leaf spot of sweet potato

Passalora leaf spot is a fungal disease of sweet potatoes caused by the pathogen Passalora bataticola. This disease is a significant concern for producers, as it targets the foliage, which is essential for photosynthesis and energy accumulation in the storage roots of the plant.

The primary host for this fungus is the sweet potato (Ipomoea batatas). The disease manifests primarily on leaves, where it interferes with the plant's metabolic functions. If left unchecked, the spread of the pathogen can lead to severe defoliation, particularly in high-density plantings with poor air circulation.

Symptoms initially appear as small, chlorotic or light-colored spots on the leaves. As the disease progresses, these spots expand, turning dark brown or necrotic with a distinct margin. Under high humidity, a characteristic fungal growth, containing spores, may develop on the underside of the leaves, appearing as a fine fuzzy mat.

The development and spread of Passalora bataticola are favored by warm temperatures and extended periods of leaf wetness, such as frequent rain, fog, or heavy dew. The fungal spores (conidia) are easily disseminated by wind currents and splashing water. The pathogen survives between seasons on crop residues, making sanitation a critical aspect of field management.

The economic impact is primarily due to reduced yields caused by premature senescence of the foliage. To effectively manage this disease, growers should adopt integrated pest management practices:

• Implement strict crop rotation schedules to break the pathogen cycle.
• Ensure proper field sanitation by removing and destroying infected plant debris.
• Use certified disease-free planting material to prevent initial outbreaks.
• Apply preventative fungicides when weather conditions are conducive to disease development.