Shot hole disease

The causal agent of this plant disease is the fungus Pruniphilomyces circumscissus, formerly classified as Clasterosporium carpophilum. It is a widespread pathogen primarily affecting stone fruit trees, leading to the condition colloquially known as shot hole disease.

The disease impacts various fruit species, including peaches, apricots, plums, cherries, and almonds. Both young nursery stock and mature, productive orchard trees are vulnerable to infection, which can lead to severe physiological stress if left unmanaged.

Symptoms initially appear as small, reddish-brown spots on leaves. As the lesion matures, the necrotic tissue dries and falls out, resulting in the characteristic perforations or "shot holes" across the foliage. Fruit symptoms involve depressed spots that may turn into scabby lesions, often accompanied by gumming.

Development and spread of the fungus are favored by wet, humid, and moderately warm conditions. The pathogen overwinters as mycelium in infected buds, twigs, and bark lesions. During the growing season, spores are disseminated by wind-blown rain and overhead irrigation, facilitating rapid infection of healthy tissue.

The economic impact of this disease is significant, as it leads to premature defoliation, reduced fruit quality, and weakened tree structure due to twig dieback. Integrated management strategies are essential for effective control:

• Pruning and removal of infected twigs during the dormant season.
• Application of copper-based fungicides during the delayed dormant stage.
• Use of protective fungicides during wet spring weather.
• Sanitation practices, including the removal of fallen infected leaves.