Disease in a Leyland Cypress


The Leyland cypress is a pyramid-shaped evergreen that has a growth rate averaging approximately 3 feet per year. This rapid growth rate makes the Leyland cypress a candidate for hedges, windbreaks, and privacy screens. Its branches have a soft feathery appearance, and its needles, when broken, are fragrant. This lovely tree is a popular choice in landscape design. It is susceptible to several diseases such as: seiridium canker, botryosphaeria (Bot) canker, and Phytophthora and Annosus root rots.

Tree Characteristics

The foliage of the Leyland cypress is dark green, and it maintains this color throughout the year. It is a hybrid of the Monterey cypress and the Nootka false cypress. A mature Leyland cypress may reach a height of up to 70 feet. It should be grown in an organically rich, moist well-drained soil. The root system of the Leyland cypress is shallow, and it will not do well in extreme or long-lasting drought conditions. It is important to keep the Leyland cypress stress free as stressed trees are more likely to succumb to disease.

Canker Diseases

Seiridium canker and botryosphaeria canker are fungal diseases. The symptoms of both fungal diseases are similar--you will notice a yellowing or browning of the needles, which begins on the top lateral branches of the tree. These symptoms generally occur in the spring season. This yellowing progresses to other branches of the tree, and eventually a large part of the tree dies. After the fungus invades the tree cankers form on the twigs, branches and the trunk. In seiridium cankers, often you will see resin oozing from the cankers. Fungal cankers produce fruiting bodies, which appear as pencil lead sized black dots on the cankers.


Both seiridium and botryosphaeria canker are spread by fungal spores. The spores are spread when it rains, through irrigation, or through using infected pruning tools. Bot canker can also be spread by the wind.

Controlling Canker Diseases

The control methods are the same for both canker diseases, with the best control being maintaining a healthy tree, as these cankers cannot be controlled with chemical applications. Pruning should be kept to a minimum to avoid wounds--wounds provide an entry point for the disease, although you will need to prune infected branches as soon as possible. Diseased plant material should be destroyed. Pruning tools should be disinfected with alcohol or bleach to avoid spreading the disease.

Root Diseases

The Leyland cypress is susceptible to two root diseases: Phytophthora root rot, and Annosus root rot. Trees with severe Phytophthora root rot will have yellowing of the needles and branch dieback. The symptoms of Annos root rot are yellowing of the needles, a slow decline of the tree, and eventual death of the tree. In some instances there may not be any visible signs of Annos root rot--the tree will just fall over. There are no effective chemicals that can be applied to control Phytophthora or Annos root rot.

Keywords: Leyland cypress tree, canker diseases rot, yellowing leaves dieback

About this Author

Paula M. Ezop’s inspirational column "Following the Spiritual Soul" appeared in "Oconee Today," a Scripps Howard publication. She has published her first book, "SPIRITUALITY for Mommies," and her children's chapter book, "The Adventures of Penelope Star," will be published by Wiggles Press. Ezop has a Bachelor of Arts degree from Northeastern Illinois University and has been writing for 10 years.