The Leyland cypress tree has soft, feathery branches. It is a pyramid-shaped evergreen whose needlesare extremely fragrant when broken. A mature tree can reach a height of up to 70 feet. The Leyland cypress tree has become a popular element in landscape design, and is known for its dark green foliage. This fast growing tree--generally 3 feet per year--is used extensively as a hedge, windbreak, or privacy screen. Diseases that it is susceptible to include seiridium canker, botryosphaeria (Bot) canker, and Phytophthora and Annosus root rots.
Providing a Healthy Environment
Leyland cypress is a hybrid of the Monterey cypress and the Nootka falsecypress. It requires a site with organically rich, moist, well-drained soil. Since the root system of the Leyland cypress is shallow, it will also need adequate watering during extreme/long-lasting drought conditions. Providing the correct soil conditions as well as monitoring watering during drought conditions will help to keep the Leyland cypress tree stress free. Stress free trees are less susceptible to disease.
There are two canker diseases that can attack the Leyland cypress tree. They are: Seiridium canker and botryosphaeria canker. Both cankers are fungal diseases. Symptoms of canker disease usually occur in the springtime. There will be a yellowing or browning of the needles, beginning on the top/lateral branches. As the disease progresses this yellowing or browning will be apparent on other branches of the tree--resulting in the death of a large part of the tree. Cankers form on twigs, branches and the trunk of the tree. These cankers will produce miniscule fruiting bodies.
Spreading of Canker Diseases
Fungal spores spread the cankers. They can be dispersed when it rains, when the tree is watered or irrigated, or by using pruning tools that are infected with the disease. This is how both seiridium and botryosphaeria canker are spread. Botryosphaeria canker spores can also be dispersed by the wind.
How to Control Canker Diseases
There are no known chemicals that can control seiridium or botryosphaeria canker disease. Your best means of control is to maintain a healthy tree (stress free). Diseased branches should be pruned and infected plant material destroyed. Pruning tools should be disinfected to avoid spreading the disease. Disinfect tools by dipping the cutting blades in either alcohol or bleach. Keep regular pruning to a minimum to limit any open wounds that serve as an entry point for disease.
Phytophthora and Annosus Root Rot
Phytophthora root rot and Annosus root rot are two root rot diseases the Leyland cypress tree is susceptible to. Symptoms of severe Phytophthora root rot are yellowing of the needles and branch dieback. Symptoms of Annosus root rot are yellowing of the needles, a slow decline of the tree, and eventual death of the Leyland cypress. Sometimes you will not see any signs of root rot because all signs will be under the soil; the tree may just fall over. Just as with the canker diseases, there are no effective chemicals that can be applied to control Phytophthora or Annosus root rot.