🦠 Shot Hole Fungus

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Shot hole disease, also known as coryneum blight, is a fungal disease primarily affecting Prunus species, including stone fruit trees like peaches, plums, and cherries, as well as ornamental trees like flowering cherries and English laurel. The disease is caused by the fungus Wilsonomyces carpophilus (formerly Coryneum), and it gets its name from the characteristic "shot hole" appearance it creates on leaves. 

Disease Cycle:

  • The fungus overwinters in infected buds and twigs. 

  • Spores are released in the spring, especially during wet conditions, and spread by rain and wind. 

  • Infections can occur on leaves, fruit, and young twigs. 

  • Prolonged wetness favors disease development, particularly during the fall and winter (twig blight) and spring (fruit infection)

Management:

Cultural Practices:

  • Pruning: Prune out and destroy infected twigs and branches during the dormant season.

  • Watering: Avoid overhead watering and use drip irrigation or low-volume sprinklers to minimize leaf wetness.

  • Sanitation: Remove fallen leaves and debris where the fungus can overwinter.

Chemical Control:

  • Dormant Sprays: Apply copper-based fungicides or other approved fungicides in the fall after leaf drop or before bud break in the spring.

  • Spring Sprays: Fungicide applications may be needed during bloom or shuck fall (when petals fall) if wet conditions persist.

  • Important Considerations:

  • Early detection and intervention are crucial:

  • Inspect trees regularly for symptoms and take action promptly.

Michael Wei