Cherimoya rust

Cherimoya rust is a fungal disease caused by the pathogen Phakopsora cherimoliae. This fungus belongs to the order Uredinales and specifically targets plants within the Annonaceae family, most notably the Annona cherimola tree. It is recognized as a significant constraint in regions where cherimoya and related species are cultivated commercially.

The primary hosts for this pathogen are species of the Annona genus. The disease can affect various stages of the tree's development, but it is most frequently observed in mature orchards where dense foliage creates a microclimate conducive to fungal growth and the rapid spread of spores throughout the canopy.

Symptoms are identified primarily on the leaves. Infected plants display small chlorotic spots on the adaxial surface, which correspond to the development of orange-brown uredinia (spore pustules) on the abaxial side. As the disease progresses, these lesions may merge, causing extensive necrosis, leaf curling, and severe premature defoliation of the tree.

The development and spread of Phakopsora cherimoliae are heavily reliant on environmental factors. High relative humidity and the presence of leaf surface moisture (dew or rain) are essential for spore germination and infection. Wind currents act as the primary vector, facilitating the long-distance dispersal of urediniospores during humid, warm weather conditions.

The economic impact of this disease is linked to reduced photosynthetic capacity, which directly results in stunted growth and lower fruit quality. Effective management involves an integrated approach:

• Pruning to improve air circulation within the tree canopy.
• Strict sanitation protocols including the removal of infected plant debris.
• Application of appropriate fungicides during high-risk humid periods.
• Monitoring orchard health to enable early detection and intervention.