|What causes the some branches on Leland Cypress trees to turn brown and other branches on the same tree to appear healthy? What can I do to prevent this occurance? Also,does fertilizing the trees help?
|It's difficult to diagnose the problem with your Leyland cypress without actually seeing it! Seiridium and Botryosphaeria cankers, Cercospora needle blight, and Phytophthora and Annosus root rots are all common afflictions. With Seiridium and Botryosphaeria, cankers appear as sunken, dark brown or purplish patches on the bark, often accompanied by extensive resin flow. It should be noted that resin exudation often occurs from the branches and stems of otherwise healthy plants of Leyland cypress thus resin flow by itself is not a diagnostic characteristic for Seiridium canker. Scattered twigs or branches killed by the fungus turn bright reddish brown, and are in striking contrast to the dark green healthy foliage. Fruiting bodies of the fungus appear on the bark surface of the cankers as small circular black dots barely visible to the naked eye. Spores of the fungus are spread to other parts of an infected tree, or from tree to tree by water splash from rain or irrigation. Prune out and destroy dead branches. Effective chemical control is not available.
The first symptom of Cercospora needle blight is a browning of the needles in the lower crown next to the stem. The disease slowly spreads upward and outward until, in severe cases, only the needles at the tips of the upper branches remain green. Cercospora needle blight can be controlled by spraying with copper-containing fungicides according to label directions.
Root rots are typically found in root systems where the drainage is poor. While I can't diagnose the problem with your Leyland cypresses, I hope this information is helpful.