Sirococcus clavigignenti-juglandacearum: An Undescribed Species Causing Canker on Butternut

Abstract

Widespread dying of butternut (Juglans cinerea L.) was reported first in Wisconsin in 1967 (Renlund, 1971). The number and extent of the diseased areas, the deterioration of the dead trees, and the determination of canker age by ring count indicated that the disease has been active for several years (Kuntz et al., 1977). Butternut canker since has been found throughout the range of butternut in the midwestern and eastern United States (Anderson and LaMadeleine, 1977). An undescribed fungus has been isolated from diseased specimens collected in several midwestern states. Repeated inoculations of seedlings, saplings, and mature trees of butternut have demonstrated its pathogenicity according to Koch's postulates. Diagnostic symptoms of butternut canker include discrete, elliptical to fusiform cankers involving the bark and wood of twigs, branches, stems, and even exposed buttress roots (Kuntz et al., 1978). Young cankers commonly originate at leaf scars, buds, lenticels, bark wounds, including insect wounds, natural bark cracks, and occasionally at points free of apparent injury. Older cankers on trunks are large, open or partly 641