Shot hole disease

The pathogen Wilsonomyces carpophilus is a fungal organism belonging to the Ascomycota division. It is the primary causal agent of shot hole disease, a widespread and destructive fungal infection that affects various stone fruit trees across temperate climate zones worldwide.

The disease primarily targets species within the Prunus genus, including peach, nectarine, apricot, cherry, and plum trees. Symptoms manifest on leaves, buds, blossoms, twigs, and fruit, resulting in necrotic spots that eventually drop out, leaving behind the characteristic shot-hole appearance that gives the disease its common name.

The life cycle of the pathogen is centered on its ability to overwinter as mycelium within infected buds and twig cankers. As environmental conditions become favorable during the spring, the fungus produces conidia, which are then disseminated by splashing rain and wind to infect developing leaves and young fruit tissues.

Development and spread of the fungus are highly dependent on moisture levels. Prolonged rainy weather and moderate temperatures are ideal for spore germination and colonization of host tissues. Without adequate management, the pathogen can thrive throughout the growing season, causing significant premature leaf drop and fruit damage.

Control strategies for shot hole disease require a combination of cultural and chemical interventions. Pruning and removal of infected twigs during the dormant season are essential to reduce inoculum levels. Fungicide applications, particularly using copper-based products, are critical during the late autumn leaf drop and early spring bud swell stages to effectively manage the disease.