Branch Canker and Dieback
this tree is particularly susceptible to a branch canker or branch dieback.
This disease may be actually caused by two fungi, Seiridium unicorn or Botryosphaeriadothidea.
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.
Botryosphaeria canker produces symptoms similar to Seiridium canker. This canker
disease affects many woody ornamentals.
Symptoms and damage
Both disease organisms attack
plants that are stressed by environmental factors, such as wounds,drought and freezing
.The mostobvious indication of the disease is thebrowning 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 both fungal organisms can often be seen within these areas. Affected
branch tips turn yellow or brown.
The affected branches are usually randomly distributed on the tree.
This random distribution of branch dieback is useful in disease diagnosis. 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 gummosistype 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.
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 these two canker diseases
are 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. In nursery situations, containergrown trees should be protected from prolonged
periods of subfreezing temperatures, which may create wounds on the stems. Do not
take and propagate cuttings from infected plants. If Leyland cypress is to be grown
as a screen, be sure to have a minimum of 12 to 15 feet between plants. 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 www.uaex.edu. Early detection and
identification are important for effective disease management strategies. For further
information about Seiridium canker and other diseases of Leyland cypress, contact
your local county Extension office.