Shothole disease

Shothole disease, caused by the fungus Coryneum carpophilum, is a significant fungal infection affecting stone fruit trees. This pathogen targets leaves, buds, blossoms, and fruits, often leading to severe defoliation and reduction in crop quality, which can compromise the tree's overall vigor.

The disease primarily affects species within the Prunus genus, including peaches, apricots, nectarines, plums, and cherries. The fungus survives unfavorable conditions as mycelium in tree cankers or as dormant spores, re-emerging in early spring when environmental conditions become conducive to fungal activity.

Symptoms are distinct and easily identifiable: small, reddish or brown spots appear on leaves, which eventually drop out, leaving behind a series of small, ragged holes—hence the name "shothole." On the fruit, the disease causes small, sunken spots that may develop into scabby lesions, frequently accompanied by significant gumming on twigs and branches.

The spread of Coryneum is heavily dependent on moisture. Rain and high humidity facilitate the dispersal of spores from lesions to healthy tissue via splashing droplets. Periods of prolonged wet weather during the spring are critical for infection outbreaks, making orchard sanitation and timely monitoring essential for effective control.

Integrated pest management is the most successful approach to controlling shothole disease. Prevention relies on pruning infected branches during dry weather, maintaining a clean orchard floor to reduce inoculum levels, and improving air circulation through proper canopy management. Fungicide applications, particularly copper-based sprays during the dormant season and protective treatments before bud break, are vital for managing severe outbreaks.