Effect of non-volatile metabolites of Trichoderma harzianum together with certain salts containing Mg ++ , Fe +++ , Mn ++ , Cu ++ , Al +++ , Ca ++ , K ++ , Na + , PO 4 ---and SO 3 ---on the production and length of rhizomorphs of Armillaria borealis, A. gallica and A. ostoyae was studied. In pure medium, T. harzianum exhibited stimulating effect on rhizomorphs of A. borealis (both number and length) and A. ostoyae (only initiation).Cu ++ salt totaly inhibited the initiation of rhizomorphs of Armillaria borealis, A. gallica and A. ostoyae. Effect of other compounds on the activity of T. harzianum depended on Armillaria species. The majority of chemical compounds tested supressed the activity of non-volatile metabolites of T. harzianum. Evident stimulating effect was observed under influence of sulphate salts consisting Al ++ and Fe +++ on the rhizomorph number of A. borealis and A. gallica, respectively.