ATROPELLIS CANKER OF LODGEPOLE PINE: ETIOLOGY, SYMPTOMS, AND CANKER DEVELOPMENT RATES

Abstract

The reproductive structures of Atropellis piniphila (Weir) Lohman and Cash are described from material collected on lodgepole pine in Alberta. Conidia probably precede apothecia. They are produced endogenously and are released in a mucilaginous exudate when the fructifications are wet. Inoculations and subsequent reisolations provide strong evidence of the pathogenicity of A. piniphila, although only a few of the inoculations were successful.The pathogen entered through undamaged bark, and most stem infections originated on stems at branch nodes. Some stem cankers originated as branch infections in a stand where the lower branches were alive, but none originated in this way where live branches were restricted to the upper crown. In stands with large amounts of inoculum, the likelihood of stem tissues becoming infected changed as tissues grew older. An initial period of very low likelihood of infection was succeeded by one of high likelihood, and this in turn by a period of low likelihood.The development of symptoms is described, and the rates of longitudinal and tangential development of cankers are given.