Cypress trees include a variety of landscape trees and shrubs that thrive in northern temperate regions. These prolific climbers grow 2 to 3 feet every year, reaching heights of more than 70 feet. Although cypress trees are generally known to be pest and disease-resistant, some diseases arise that adversely affect their health, thus requiring immediate attention.
Cercospora Needle Blight
Cercospora Needle Blight is a fungal disease common in Leyland cypresses. This disease causes needles located on the inner branches near the base of the tree to turn brown. It spreads upwards and outwards until only the needles located on the highest branches remain green. Cut off the diseased branches to prevent the spread of disease to other parts of the tree, and treat affected areas with a fungicide that contains copper. Spray the fungicide every 10 days from the time buds arise until they mature.
Annosus Root Rot
Annosus Root Rot is a serious disease that occurs in Italian and Leyland cypress trees. According to the North Carolina State University's Plant Pathology Extension, this fungus appears on freshly cut stumps pines and other conifers, and spreads to adjacent trees. Symptoms include a sudden change in foliage color from green to reddish-brown. No effective measure to control or save affected cypress trees exists. Remove the stump from the soil completely or treat exposed stump surfaces by spreading a thick layer of granular borax over it to keep it from spreading.
Phytophthora Root Rot
Another type of root rot that affects cypress trees is the Phytophthora Root Rot, caused by the Phytophthora cinnamomi--a water mold that exists in the soil and targets younger cypress trees instead of established and mature ones. It occurs where soil drainage is poor, and affected trees exhibit yellowing of foliage. Send samples of affected roots to a local laboratory for analysis that confirm the existence of the mold pathogen.
Caused by Seiridium unicorne, this canker is known to be the most damaging disease to affect cypress trees and plants of all sizes, specifically Leyland cypress, and causes infected twigs, stems and branches to die back. Affected branches turn reddish-brown and the fungus spreads to other parts of the cypress tree or to other trees from shared pruning tools or irrigated water. Although no chemical control exists, reduce chances of spread by pruning affected areas 1 inch below the canker and discarding foliage in a knotted garbage bag. Sterilize pruning equipment before and after use.
Cypress trees affected by Botryosphaeria Canker feature scattered, reddish-brown dead twigs amidst healthy foliage. The fungus Botryosphaeria dothidea, comonly called Bot, causes this disease in cypress trees. Although visible symptoms are similar to the Seiridium Canker, run your hand over the affected areas to determine whether the needles remain intact or fall off. If the needles do not fall, the disease is Botryosphaeria Canker. Watering the cypress tree during dry periods reduces the chances of this disease. Sterilize pruning equipment to minimize the likelihood of spread.