Diaporthe wilt of cashew

The disease is caused by the fungal pathogen Diaporthe anacardii, an ascomycete fungus. This pathogen is known for its ability to invade and damage the internal tissues of host plants. It primarily affects the vascular system and cortical layers, disrupting the normal physiological processes and nutrient flow throughout the plant.

The primary host for this fungus is the cashew tree (Anacardium occidentale). While other related species can potentially act as hosts, the economic impact is most significant in cashew plantations. The infection can lead to substantial losses in yield and, in severe cases, the eventual death of the affected trees.

Symptoms of Diaporthe wilt include leaf yellowing followed by rapid wilting and necrosis. You can often identify the disease by observing the dark, sunken lesions that appear on the stems and branches. Eventually, these lesions coalesce, leading to dieback, where the tips of branches dry out and turn black, giving the canopy a scorched appearance.

The spread and development of the disease are heavily dependent on environmental conditions. High humidity, frequent rainfall, and warm temperatures create the ideal environment for the spores to germinate and infect new tissues. The fungus disperses via rain splash, wind, and human activities, particularly through contaminated pruning equipment used across the plantation.

Management and prevention strategies focus on limiting the pathogen's ability to survive and spread:

• Strict sanitation practices, including the removal and destruction of dead or infected branches.
• Sterilization of pruning tools using appropriate chemical disinfectants after working on each tree.
• Application of copper-based fungicides or other systemic fungicides as a preventative measure during the wet season.
• Maintaining optimal plant spacing to promote better airflow and reduce humidity levels within the canopy.
• Regular field monitoring for early symptoms to intervene before the disease spreads.