BLACK STEM GALLS ON ASPEN AND THEIR RELATIONSHIP TO DECAY BY PHELLINUS-TREMULAE

Efficient use of trembling aspen (Populus tremuloides Michx.) is often limited by the presence of extensive decay and stain. Aspen trees wit h black stem galls of unknown cause reportedly have less advanced deca y caused by the fungus Phellinus tremulae (Bond.) Bond. and Boriss. th an do adjacent trees without galls. Nine field sites having large numb ers of galled aspen were surveyed for the presence of P. tremulae conk s. Logistic regression showed that the odds of a gall tree having at l east one conk was 44% of that for trees without galls, and that the oc currence of conks varied among sites and increased with increasing tre e diameter. Inclusion of black galls in models used to predict decay m ight result in greater accuracy on sites where these galls are prevale nt. Black galls may also be potential sources of biological control ag ents against decay-causing organisms in aspen.