Avocado scab

Sphaceloma perseae is a pathogenic fungus belonging to the kingdom Fungi and the genus Sphaceloma. It is the primary causal agent of avocado scab, a major disease affecting Persea americana globally. This fungus specifically targets the aerial parts of the tree, leading to significant economic losses for commercial avocado growers.

The disease is characterized by the appearance of small, raised, corky spots on leaves, stems, and fruits. As the infection progresses, these lesions merge, creating rough, unsightly patches on the skin of the avocado fruit. While the internal quality of the fruit remains largely unaffected, the external scarring makes it commercially unattractive for fresh market sale.

The life cycle of the pathogen is driven by environmental moisture. Conidia are spread primarily through rain splash, wind, and movement of equipment or tools through the orchard. Young, tender tissues are highly susceptible to infection, and the pathogen can complete its cycle rapidly when environmental conditions remain conducive to fungal growth.

Optimal conditions for Sphaceloma perseae include high humidity, frequent rainfall, and warm temperatures. These factors promote the germination of spores and the subsequent colonization of the plant surface. In regions with prolonged wet seasons, the disease can become endemic, requiring consistent monitoring and preventative action.

Management and control strategies focus on reducing the inoculum and protecting vulnerable tissues. Sanitation, such as pruning infected branches, is essential to minimize the source of spores. Regular applications of copper-based fungicides during the fruit-set stage are widely considered the most effective chemical control method to prevent the development of lesions on the fruit.

• Raised corky lesions on fruit skin
• Spread via rain splash and irrigation
• Susceptibility of young, non-hardened tissue
• Importance of orchard sanitation
• Copper-based fungicide applications