• The Leyland cypress is also known by its scientific name Cupressocyparis leylandii and is commonly used as a hedge, screen or a Christmas tree. At maturity, the Leyland cypress can reach heights of 70 feet or more. While typically healthy, the Leyland cypress can develop diseases which affect the appearance and health of the tree.
  
  

Seiridium Canker

• According to North Carolina State University, Plant Pathology Extension, Seiridium canker is the most damaging disease to affect Leyland cypress. This disease is caused by the fungus Seiridium unicorne and affects the Leyland cypress at any stage. The symptoms most commonly associated with Seiridium canker include the development of brown cankers on plant parts; bark and affected branches die and turn reddish-brown in color. Tiny black dots known as fruiting bodies often develop on the bark of the tree. At this time, there are no known preventive or chemical control measures proven to eliminate Seiridium canker. Avoid drought stress and avoid wounding trees to prevent infection. Serious infections often result in the removing and destroying of the affected Leyland cypress.
  
  

Bot Canker

• Botryosphaeria canker is more commonly known as Bot canker. This disease causes extensive damage in Leyland cypress. Bot canker is caused by the fungus Botryosphaeria dothidea, which is an aggressive fungus. The Alabama Cooperative Extension System states that other plants such as the azalea, flowering dogwood and rhododendron are also affected by this disease. Stress from drought and heat are two causes of Bot canker. The symptoms associated with Bot canker in Leyland cypress include foliage that turns yellow or brown, canker girdling the plant and the plant tissue below the canker turning brown. Preventing Bot canker in Leyland cypress is best accomplished by placing mulch around the tree to hold in moisture and avoiding drought stress. Avoid injuring the tree trunk during pruning or mowing, and prune discolored or unhealthy branches immediately. At this time, there are no fungicides recommended in the treatment of Bot canker.
  
  

Needle Blight

• Cercospora needle blight is caused by the fungus Cercosporidium sequoiae. This fungal disease is fairly new to the Leyland cypress, but can cause browning of the needles, which is the first symptom of disease. Needle browning usually begins in the lower portion of the tree and spreads upward. Leyland cypress infected with Cercospora needle blight can turn almost totally brown, with only needles at the tips of upper branches remaining green, reports North Carolina State University. Cercospora needle blight is transmitted to other trees by spores, which are carried on the wind. Spraying Leyland cypress with fungicides that contain copper may help prevent and eliminate this disease.