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Leyland Cypress

Seiridium canker, caused by Seiridium unicorne, is probably the most damaging disease on Leyland cypress.  Cankers appear as sunken, dark brown or purplish patches on the bark, often accompanied by extensive resin flow. Scattered twigs or branches killed by the fungus turn bright reddish brown, and are in striking contrast to the dark green healthy foliage.  Currently there are no chemical control measures recommended for the disease in the landscape or nursery. Avoiding water stress and tree wounding may reduce infection. Infected branches or twigs should be pruned and destroyed as soon as symptoms are noted.

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