A CANKER AND FOLIAGE DISEASE OF YELLOW BIRCH: I.’ DESCRIPTION OF THE CAUSAL FUNGUS, DIAPORTHE ALLEGHANIENSIS SP. NOV., AND THE SYMPTOMS ON THE HOST

Diaporthe alleghaniensis R. Horner Arnold, sp. nov., is described and illustrated in both the ascigerous and conidial (Phomopsis) states, and the cultural characters are given. This is the first species of Diaporthe described on the host Betula alleghaniensis Britt. It is distinguished morphologically from known species of Diaporthe by the narrow cylindrical ascus with truncate apex and by the narrow cylindrical-ellipsoid ascospores with variable position of the single septum. It is a facultative parasite of yellow birch (B. alleghaniensis) on which it causes an annual bark canker and foliage disease. The symptoms of the disease are described and illustrated.