Seiridium cardinal will destroy the bark of the tree and will eventually cause the tree to die off. Predominately being a cause of death for cupressus conifers such as Monterey Cypress and Macrocarpa. Spores are carried by the wind, insects and also by the feet of birds entering the plant through natural cracks in the bark, through wounds caused by boring insects and through wounds caused by gardening equipment or falling branches. The fungus interferes with the sap-conducting system, eventually causing death of a branch or main trunk above the wound. Older trees are usually more susceptible to the disease, but any tree can succumb if it is stressed, for example by drought or nutrient deficiency.
Most commonly the tree will start to die from the top down, however assorted dead branches appearing at random over the tree, with sap oozing from splits and cracks on the trunk is also an indicator. Branches die rapidly, yellowing almost overnight as the foliage is starved of sap. Conifers planted in avenues or rows tend to be more affected by the disease.