A Technical Report from The Bartlett Tree Research Laboratories 355
Seiridium canker is a fungal disease that affects members of the plant families Cupressaceae and Taxodiaceae. In landscapes, Seiridium canker is most severe on Leyland cypress, Italian cypress, and Monterey cypress. The disease progresses in the canopy from the lower canopy to the higher branches, causing dieback of branch tips or whole branches making them unsightly. Because infections are favored by high leaf wetness and shade, the disease is more severe in dense plantings and older trees with extremely dense canopies.