Powdery mildew of cassava

Powdery mildew of cassava is a fungal disease caused by the pathogen Oidium manihotis. This disease specifically affects cassava (Manihot esculenta), a staple crop in many tropical regions, potentially causing severe damage to the photosynthetic capacity of the plant canopy.

The disease is characterized by the appearance of a white or grayish powdery fungal growth on the surfaces of leaves, petioles, and young stems. As the infection progresses, the leaves may show signs of yellowing (chlorosis), curling, and premature senescence, eventually leading to significant leaf drop across the affected plantation.

The development of Oidium manihotis is favored by periods of high humidity and moderate temperatures, which are common in many tropical climates. The fungus produces large numbers of conidia, which are easily disseminated by wind currents, allowing the disease to spread rapidly from infected plants to healthy ones.

The economic impact of this disease is primarily linked to the reduction in the accumulation of starch in the tubers. Because the plant loses its foliage prematurely, it cannot synthesize enough carbohydrates to support root development, leading to substantial yield losses that can reach up to 50% in highly susceptible varieties.

Management practices focus on an integrated approach to mitigate the damage caused by the pathogen. Producers are encouraged to prioritize the cultivation of resistant or tolerant varieties of cassava. Additionally, maintaining proper field hygiene, such as removing infected debris, and applying sulfur-based or systemic fungicides during early stages of infection can significantly reduce the pressure of the disease.