Pathogen
Climacodon septentrionalis is known as the northern tooth fungus (Luley 2022).
Hosts
Based on the samples submitted to the UMass Plant Diagnostic Laboratory, sugar maple (Acer saccharum) is the primary host in southern New England. Less common hosts include silver maple (A. saccharinum), American beech (Fagus grandifolia), and European beech (F. sylvatica). Occasionally, Climacodon can be found on birch (Betula), hickory (Carya), oak (Quercus), apple (Malus) and elm (Ulmus) (Sinclair and Lyon 2005).
Symptoms & Signs
Climacodon causes a spongy, white trunk rot of deciduous hardwoods in both forests and managed landscapes. The fungus primarily invades upper trunk wounds or frost cracks but can also colonize branch stubs. When codominant canopy leaders are present, the union with the main trunk is often an infection point. Basal trunk wounds may also serve as infection points. Symptoms of infection on sugar maple may include bulges and swollen sections of the lower trunk, especially at codominant leader unions. More often, no observable symptoms are present and the only indication of the disease are the large, annual fruiting bodies produced by Climacodon. These mushrooms consist of many, shelf-like layers that are cream-colored to pale yellow when fresh, becoming grey-brown with age. They can persist on infected trees for many weeks and typically form in late summer to early autumn (mid-August to mid-September). The underside of the mushroom consists of numerous small spines or teeth, which bear the fungal spores, hence the common name northern tooth fungus. The decay column can extend up to 4 m (13 ft.) above visible mushrooms and 1.5 m (5 ft.) below. Spores are wind-dispersed to infect nearby, susceptible trees.
Management
Infected trees with annually produced mushrooms can persist in the landscape for many years with relatively few symptoms of disease (Luley 2022). In many cases, these trees can remain structurally stable despite infection. Meaning, the incidence of Climacodon alone is not justification for removal. However, when the fungus is confirmed, a thorough risk assessment should be performed by a certified arborist. Advanced decay detection techniques, such as resistance drilling or sonic tomography, may be required to understand the extent of the damage. For sugar maples, avoid wounding the trunk to reduce possible points of entry for the fungus. This includes basal wounds from lawn care equipment. When the disease is confirmed, nothing can be done to eradicate the fungus and fungicides will have no effect.
References
Luley, CJ. 2022. Climacodon septentrionalis. In: Wood Decay Fungi Common to the Northeast & Central United States, 2nd Edition. Urban Forest Diagnostics LLC, Naples, NY. Pp. 88–89.
Sinclair WA and Lyon HH. 2005. Diseases of Trees and Shrubs, 2nd edn. Cornell University Press, Ithaca, NY.