The relation of bark moisture to the development of canker diseases caused by native, facultative parasites VII Some effects of the saprophytes on the bark of poplar and willow on the incidence of Hypoxylon canker
Bier, J.E.; Rowat, M.H.
Canadian Journal of Botany 40(1): 61-69
ISSN/ISBN: 0008-4026 DOI: 10.1139/b62-007
In culture studies, H. pruinatum was inhibited by natural bark extracts of Populus trichocarpa and a Salix sp., and by extracts of two of the most common saprophytes (one a Pullularia sp.) prevalent at the nodes, lenticels, and other irregularities of 1- to 3-year-old bark of these species, but was stimulated by extracts from surface-sterilized bark. There was no difference between extracts from dormant or active bark. Hypoxylon, but not the saprophytes, grew at 30 degrees C., and the saprophytes, but not the pathogen, at 3 degrees . The pathogen appeared to prefer a drier medium. Under laboratory conditions, <10% of natural, watered, cuttings, but >85% of surface-sterilized watered cuttings were successfully inoculated. Saprophytes were, however, unable to prevent infection of cuttings with low turgor. Natural bark extracts applied externally to incipient cankers on surface-sterilized watered cuttings arrested the disease, whereas sterile water applied to controls did not. The presence and activity of saprophytic antagonists is thought to play an important role in the canker resistance of dormant trees.