EVALUATION OF FUSARIUM-AVENACEUM AND OTHER FUNGI FOR POTENTIAL AS BIOLOGICAL-CONTROL AGENTS OF INVASIVE RUBUS SPECIES IN BRITISH-COLUMBIA

Fungi were isolated from naturally infected Rubus strigosus, R. parvif lorus, and R, spectabilis plants in an attempt to identify biological control agents for these invasive species in reforestation sites. Thre e endemic fungi, Fusarium avenaceum, Colletotrichum dematium, and a Ph omopsis sp., were selected for further study after they were found to induce >50% leaf area necrosis when inoculated onto detached Rubus lea ves using in vitro pathogenicity tests. However, when inoculum was app lied to intact Rubus plants under shadehouse conditions, significant f oliar necrosis was not observed. Inoculum production methods, amendmen t of inocula with adjuvants, and application of low doses of glyphosat e were investigated for their effects on pathogenicity. Foliar infecti on was increased significantly when inoculum of F. avenaceum was sown on a rice-grain substrate and applied in combination with an organosil icone surfactant (0.4% Silwet L-77(R)) to R, strigosus and R, parviflo rus plants. Extraction and analysis of infested rice filtrates for met abolite production showed that a single toxin, moniliformin, was prese nt at levels of 3300 ppm. Pathogenicity of the other two fungi was not enhanced under any conditions assayed. The potential for further deve lopment of F. avenaceum as a biological control agent of weedy Rubus s pecies is discussed.