(conidial state -Cytospora kunzei) was first described by Waterman in 1955,[6] as the causal agent for the branch and stem cankers she observed on Douglas fir.
These brown needles will remain attached during the growing season and then fall off during the winter, leaving behind bare twigs and branches.
[1][2][4][8][10][11] Lesions typically begin at the bases of small twigs and develop into elliptic or occasionally diamond-shaped cankers.
Amber colored resin profusely exudes from the edges of cankers, runs down the bark, or drips onto lower branches or the ground, and then hardens into a white crust.
The lesions associated with this pathogen typically go visibly unnoticed on infected host trees for several years, due to the diseased tissue being held in place by resin.
The formation of callus at canker margins is subtle or nearly absent, usually resin is the only indication of an underlying bark lesion.
Complete girdling of the host trunk or large limbs may occur; however, this event may take several years to even decades to accomplish.
Pycnidial stromata are shaped like short cones, 1-2 mm in diameter, with fertile chambers radiating from the center and opening through a common pore at the top.
Typically, unfavorable environmental conditions such as drought, high temperatures, or site specific stresses favor development and infection of this disease.
This pathogen can be found in outer bark of what appear to be healthy branches, which indicates latent infection may occur prior to lesion development.
Dispersal of conidiospores and ascospores via running or splashing water provides evidence for the year-to-year intensification and increasing progression of symptoms.
Both spore types have also been found dispersed on the wind in the vicinity of diseased trees, yet the means of becoming airborne is still uncertain.
During periods of prolonged drought or on dry sites regular watering is important during the growing season, as well as, the application of fertilizers every few years.
Proper sanitization of tools is crucial in prevention of accidental spread of this disease; this may be done by disinfecting them by either swabbing or immersing them in a solution of 70% rubbing alcohol.