Some references refer to Seiridium canker by older fungal names such as Coryneum canker or Monochaetia canker. Within the past several years, Seiridium canker has become an increasing problem on Leyland cypress in the Southeast. Leyland cypress trees and branches infected with Seiridium are yellowish at first then turn brown to gray as the branch dies. The fungus infects through wounds or natural openings during periods of drought stress.
Infected sites are sunken, reddish in color and ooze sap profusely.
Individual cankers are long and thin and may be numerous along a branch. Collectively, the cankers interfere with water flow through the branch causing the branch to possibly wilt and die. Spores of Seiridium are produced within dark, disk or cushion-shaped acervuli. Acervuli are produced beneath epidermal cells and often rupture through the epidermis to reveal darkly pigmented spores on short, slender conidiophores. It looks very similar to Pestalotia acervuli.