Leyland cypress has yellow spots in foliage
Q: I would like your opinion on what is going on with our Leyland cypress trees. Recently one has started showing yellow spots. What can I do?
A: There are two common diseases of Leyland cypress that cause dead spots: seridium canker and bot canker. It’s easy to tell them apart. My colleague Jean Williams-Woodward does such a good job describing diagnosis, I’ll refer you to her notes,
Fortunately, the cure for both diseases is the same: apply Dihydrogen monoxide regularly.