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What is causing the holes in my peach and cherry trees?

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It sounds like the disease is shot-hole, or Coryneum blight (Wilsonomyces carpophilus).  This fungus attacks apricots, peaches and nectarines.  Classic symptoms include gummy resin-like material on buds and stems that have been infected.  The leaves develop red spots or initial infections that expand into lesions.  Eventually, the lesions abscise and fall out creating a shot hole appearance, which is what you are seeing.  Lesions can form on buds, stems, and fruit.  This pathogen spreads in moist wet conditions. 

Homeowner control of this disease is primarily based on cultural management.  Prune out all diseased wood in early spring.  Continue pruning visible infections during the growing season, but only when the weather is dry to prevent spread.  Use a 10% bleach solution to disinfest the pruners after each cut.  Remove all infected branches from the property.  This will reduce the amount of spores available for infection.  Irrigate at ground level to avoid wetting the leaves and branches.  This helps to reduce the spread of spores.  Limit the amount of nitrogen applied to the tree.  Rapid growth promotes fungal development.

If necessary, captan is a contact fungicide that is available for homeowners and can be applied during the growing season starting in spring.  Multiple applications may be necessary.  Read the label carefully for application instructions.

Posted on 22 Feb 2007

Marion Murray
Intergrated Pest Management Project Leader

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