SCLERODERRIS CANKER ( Ascocalyx [ formerly Gremmeniella ] abietina )
Scleroderris canker is a fungus that was found to be killing mature pines in the Adirondack Mountains of New York in the 1970's. Red and Scots pines were commonly affected but other species of conifers were also found to be susceptible.
Peak infection occurs May to June although infection may occur anytime during the growing season. Infected twigs are rain splashed onto new shoots, and spores grow into the vascular cambium where they remained inactive until the host becomes dormant. The fungus then begins to grow whenever temperatures are above freezing, taking advantage of the host's defenses being inactive during dormancy.
Fig. 1. Needles on a pine branch killed by Scleroderris.
Symptoms begin to appear in spring or early summer one year after infection. Shoots 12 inches or longer are likely be fully colonized. Bases of needles on infected shoots turn reddish brown while most other agents that kill conifer needles cause browning from the tip of the needle back toward the base. Infected needles can be easily pulled from the shoot. Fruiting bodies usually appear the following autumn or spring, after shoots are dead, and then minute black pustules erupt from sites where needles were attached or through other cracks in the bark.
On Scots pine the fungus usually kills only the current year's growth. Trees die only when growing points are repeatedly killed. On red pine however, the fungus has the potential to grow down the branch to the main stem and cause a girdling canker.
Because the strain of the Scleroderris canker pathogen found in New York was different from other strains in North America at the time (1974), efforts were made by state and Federal officials to limit potential spread of the fungus. Pines from this region are now quarantined and growers require an inspection and certification before shipping pine forest products out of that region. Contact your local NYS Agriculture & Markets office for more information. Pesticides are also available to try to control this disease on Christmas trees.
Fig. 2. A shoot showing needle loss characteristic of Scleroderris.
Fig. 3. Susceptible trees killed by the disease.
Return to Pest Menu