Shothole fungus also know as Coryneum blight is caused by the fungus Wilsonomyces carpophilus. In ornamental shrubs it is very common on skip laurels. The fungus overwinters in infected buds and in small twig cankers. Infections can occur (via fungal spores) from spring to fall. Rainy weather spreads spores from infected tissue to leaves and fruit by splashed and wind-blown rain. Spores require 4 hours of moisture to germinate, sometimes leading to rapid spread of the disease within a plant. (Movement from plant to plant is usually much slower.) Lesions develop fast at optimal temperatures of 70-80°F. In the fall, infections occur on leaf scars and spread to buds. Leaf infections first appear as small red spots which enlarge and become purple with a tan-white center. The spots then drop out of the leaf to leave a "shothole." Severe infections produce numerous holes and give the affected leaves a very tattered appearance. TDI has numerous biological treatments as well as conventional measures to eradicate the fungus and keep your plants protected.
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