RESINICIUM BICOLOR - A POTENTIAL BIOLOGICAL-CONTROL AGENT FOR HETEROBASIDION-ANNOSUM

After introductory competition tests in the laboratory, Resinicium bic olor was used as a a potential control agent for the conifer root rot fungus Heterobasidion annosum. Greenhouse pathogenicity tests with R, bicolor on 4-year-old seedlings of Norway spruce (Picea abies) and Sco ts pine (Pinus sylvestris) is of Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) showed moderate incidence of infection. In th ree places in Sweden, four test areas were chosen for field experiment s in first-rotation plantations and also in old forest sires of Norway spruce. Wood blocks, pre-inoculated with one strain of R bicolor, wer e buried in the soil beside stumps at 0, 1, 2, 3 and 4 months after th inning using various spatial designs. In two of the test areas, half o f the stumps were treated with a suspension of H. annosum conidia from one strain by surface spraying. After 2-3 years, stump roots were inv estigated and the length of growth of both species were noted. The ide ntity of mycelia reisolated from roots and wood debris in the test are as were confirmed by somatic compatibility tests with the original str ains. The strain of R, bicolor released was recovered from all over th e test area; the released H, annosum strain was only reisolated from t he conidia sprayed stump roots. R. bicolor had little effect on the gr owth and occurrence of H, annosum. Potential control of disease spread may arise, however, from occlusion of the pathogen from outer parts o f roots.