Seiridium canker of cypress

Seiridium canker is a serious fungal disease caused by the pathogen Seiridium cupressi. It primarily affects the bark and cambium of cypress trees and other related conifers. By disrupting the flow of water and nutrients within the vascular system, the fungus eventually leads to the death of affected branches and, if left unchecked, the entire host plant.

The host range of Seiridium cupressi includes various species within the Cupressaceae family, such as Cupressus, Juniperus, and Thuja. The disease is particularly destructive in nursery settings and landscape plantings where trees may be subjected to environmental stress, drought, or physical injury, which creates entry points for the fungal spores.

Early symptoms often involve the browning or reddening of foliage on individual branches. As the infection progresses, distinct sunken cankers develop on the stems and larger branches. These cankers are often associated with heavy resin bleeding, known as gummosis. The bark eventually cracks, revealing the underlying wood, often peppered with the small, dark pycnidia of the fungus.

The development of the disease is highly favored by warm, humid conditions which promote the spread of spores. Spores are primarily disseminated by wind-blown rain and contaminated gardening tools. Poor air circulation in dense plantings, as well as improper pruning techniques that wound the tree without subsequent protection, are key factors that accelerate the epidemic spread.

Management of Seiridium canker relies heavily on rigorous sanitation, including the pruning and immediate destruction of all infected branches at least 10–15 cm below the visible canker. Sterilizing tools with disinfectants between every cut is mandatory to prevent cross-contamination. Preventive applications of copper-based fungicides can help protect healthy tissue, while maintaining tree vigor through proper irrigation and site selection remains the best long-term defense.