Collar Rot and Basal Canker of Sugar Maple

Two types of trunk symptoms are associated with urban maple decline in Wisconsin. One is a "basal canker," caused by Fusarium spp., and the other is a "collar rot" caused by a Phytophthora sp. Phytophthora collar rot appears to be more destructive. Trunk girdling by these diseases, both occasionally observed on the same tree, was greatest on trees with severe decline (Class V) and least on trees with initial decline (Class II). Incipient cankers were found on trees still healthy in outward appearance (Class I). Buttress roots of planted trees were deeper than the roots of naturally seeded, woodland trees. Moreover, woodland trees exhibited no similar cankers. We believe that the fungi and the diseases they incide are causes of urban maple decline in Wisconsin. They may be associated with maple tree production in nurseries or with planting practices in urban situations.