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Branch canker and dieback of leyland cypress

OPINION by Jimmy Driggers | July 19, 2021 at 4:03 a.m.

In Arkansas, Leyland cypress (x Cupressocyparis leylandii) is a common, fast-growing ornamental evergreen that is suitable for screens, groupings or as an isolated landscape tree. These trees can easily grow 3 feet per year and reach heights upward of 40 feet.

In Arkansas, this tree is particularly susceptible to a branch canker or branch dieback. Seiridium canker is perhaps the most significant and damaging disease on Leyland cypress. This fungus is commonly associated with both twig cankers and twig dieback. Left unchecked, the fungus can move into the main trunk killing the entire tree.

These disease organisms attack plants that are stressed by environmental factors, such as wounds, drought and freezing. The most obvious indication of the disease is the browning and subsequent dieback of a leader or major side branch. Sunken, dark brown cankers or patches develop on the affected branches near the transition area of healthy and diseased tissues. Small, black fruiting bodies of this fungal organism can often be seen within these areas. Affected branch tips turn yellow or brown. The affected branches are usually randomly distributed on the tree. Underlying woody tissue in the cankered areas is often gray or brown. Extensive resin ooze or "bleeding" on diseased branches may also occur. This symptom resembles sap flow or gummosis type symptoms. When branches are wet from rainfall or overhead irrigation, the fungus advances rapidly, killing tissue in its wake. Entire trees may be killed if the fungi are allowed to advance into larger branches and stems.

Infection typically takes place during wet weather. Microscopic spores are disseminated primarily by splashing from overhead water. Infection occurs primarily through tree wounds; however, one species of Seiridium can penetrate intact young green leaves and shoots. Spores may lodge in bark crevices. Insects and pruning tools may also serve to disseminate spores. These canker diseases can kill large sections of the plant during the spring and summer during periods of frequent rainfall or high humidity.

Cultural practices are important in disease management. All infected branches should be pruned about 3 to 4 inches below the cankered area and destroyed as soon as symptoms are observed. As an added precaution, disinfect pruning blades after each cut with either 10 percent household bleach or 70 percent alcohol. Since this canker disease is often associated with environmental and cultural stresses, plants should be irrigated properly during lengthy drought periods. Field observations suggest that trees grown in shady conditions are more prone to develop these canker diseases. If the plants are irrigated by overhead means, this should be done during the early morning hours. By minimizing overhead water, the level of disease spread can be reduced. Currently, fungicides are not effective for controlling this disease.

Because of the widespread occurrence of this disease on Leyland cypress, homeowners may wish to consider an alternative tree for the landscape. For a list of suitable landscape trees, see FSA6126, Landscape Trees for Specific Uses, at http://[email protected] Early detection and identification are important for effective disease management strategies. If you have questions please contact Jimmy Driggers, county Extension agent-staff chair, by email, [email protected], call 501-623-6841, or come by our office at 236 Woodbine.

Master Gardener information

Master Gardener meetings are held on the third Thursday of each month at the Elks Lodge. The meetings are open to the public, and guests are welcome. For more information, call the Extension office at 623-6841 or email Alex Dykes at [email protected]

EHC information

Are you interested in joining an existing Extension Homemakers Club? EHC is the largest volunteer organization in the state. For information on EHC, call 623-6841 or email Alison Crane at [email protected] Follow Alison on Facebook @garlandEGF and @Garland FCS, and EHC on Facebook @GarlandCountyEHC.

4-H information

For information about Garland County 4-H Club membership or program benefits, call Carol Ann McAfee at the Extension office, call 501-623-6841, or email [email protected] Additional information is available at

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