Some inoculum factors in pathogenicity studies of Hypoxylon pruinatum (Klotzsche) Cke. on Populus tremuloides Michx

Inoculum type was an important factor in pathogenicity studies of Hypoxylon pruinatum (Klotzsche) Cke. on Populus tremuloides Michx. The percentages of infection from bark meal and mycelial inocula were superior to that from agar plug inoculum, irrespective of whether the bark wounds were superficial or exposed the cambium and xylem. In experiments with mycelial inoculum it was demonstrated that autoclaved and living bark without inhibiting microorganisms were favorable to the growth of the pathogen. However, mycelial growth and infection were prevented when an abundance of bark saprophytes was applied to the host before inoculation. It appeared that the susceptibility or resistance of living bark to infection may have been more closely related to microbiological than chemical factors of the host tissues