Leyland Cypress Problems
Our 10 year old Leyland Cypress trees are turning brown on the inside and in patches on the outside. In the past, when I've seen yellowing to brown patches of needles, I was told to sprinkle a little ammonium nitrate around the base. They always seemed to perk up after that. I heard that a University of Tennessee Extension expert was on our local station recently discussing this, but I missed what he said. Can you tell me what's wrong and how to fix them?
Anderson County Tennessee
Leyland cypress is very susceptible to two canker diseases: Botrysphaeria canker and Seridium canker. Though it is difficult for me to confirm using your photos, I suspect this is a possibility. There are no effective chemical treatments for these diseases. However, they won't cause your trees to die overnight-though if they are infected it will be progressive.
Leyland is also susceptible to some less detrimental diseases, inlcuding tip blight. For more specific diagnosis, consider taking a sample to your local extension office.
100 N. Main Street, Room 213
Clinton, TN 37716-3617
You can prune out infected branches to slow both disease. If the Leylands are planted in a hedge row, it is helpful to increase air flow around them. You can do this by removing individual trees.