STUMP PROTECTION AGAINST FOMES ANNOSUS II. TREATMENT WITH SUBSTANCES OTHER THAN CREOSOTE

Various substances when added to the stump surface in concentrated solution directly after felling markedly affect the course of fungal colonization. The extent to which applications kill stump tissues probably affects the rate at which saprophytes develop. Nitrogenous applications favour growth of Trichoderma viride and Penicillium spp., which tend to suppress surface colonization by Fomes annosus; ammonium sulphamate is especially effective in this respect. Some other applications are initially toxic to stump fungi but rapid leaching from the stump surface soon permits growth of various moulds, which again tend to suppress F. annosus and to a large extent other primary basidiomycete colonizers. Substances of this type include urea, which encourages growth of Ophionectria cylindrospora, and disodium octaborate, which favours Botrytis cinerea. The probable mode of action of these substances is discussed. Stumps usually die more rapidly after such treatments than after creosoting, and often as fast as untreated ones. The rapid colonization of treated stumps by saprophytes is of advantage where application is incomplete or the stump is subsequently damaged. The effectiveness of treatments in preventing a major spread of Fomes annosus from roots already containing the parasite is variable and apparently depends to some extent on the particular species becoming dominant. Preliminary screening may be performed in the laboratory with sections of pine stem inoculated with stump fungi; potential protectants are then tested in the forest.