Symptoms
Symptoms of this disease in spruce hosts include dead and dying branches and perennial lesions on the branches and trunk, which exude resins. Older branches (lower on the trees) sustain more damage than younger ones. In spring and early summer the foliage of an infected branches on host trees fade and turns brown, which is an indication of girdling occurring within a branch or along the mainstem caused by this pathogen. These brown needles will remain attached during the growing season and then fall off during the winter, leaving behind bare twigs and branches. This entire process can occur annually, moving from low branches to higher branches, thus destroying the symmetry of the host tree. Twigs and branches killed by this disease may remain on the diseased host tree for several years. All of this damage caused by this fungal pathogen does not typically begin until the host trees are at least 10–15 years old. However, in landscape nurseries small branches of young blue spruce or occasionally white spruce may be killed.
Lesions typically begin at the bases of small twigs and develop into elliptic or occasionally diamond-shaped cankers. Lesions that originate on branches close to the main stem may actually spread into the main stem. Cambium that has been killed by this disease has a brown to reddish brown internal coloration and is saturated with resins. The underlying sapwood, which has been killed and colonized by the pathogen, is rarely discolored. 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. Cankers formed on the trunk will eventually appear as sunken due to living tissues (callus) expanding and growing around the wounded tissues. Complete girdling of the host trunk or large limbs may occur; however, this event may take several years to even decades to accomplish. In other susceptible conifers, symptoms are similar to those of spruce except resin exudation is usually less prominent. Regarding pines the key symptom to note is the inconspicuous branch cankers caused by this pathogen.
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