BIOLOGICAL TREATMENT FOR PLANTING APPLE-TREES IN SOIL PREVIOUSLY PLANTED WITH CHERRY TREES IN THE KOOTENAY VALLEY OF BRITISH-COLUMBIA

Field trials conducted in the Kootenay Valley during 1989 to 1991 established that the root-dip application of strain EBW4 of Bacillus subtilis alone was effective in increasing the growth of apple trees planted in old cherry orchard soil that was conducive for replant disease. The response was measured by increases in cross-sectional trunk area and shoot height of Jonagold apple trees on (Malus domestica Borkh.) M.9 rootstock. Strain EBW4 of B. subtilis applied as root-dip in combination with metham-sodium fumigation, peat, or NPK fertilization, was also effective in promoting growth of apple trees but not as consistently as when it was applied alone. Metham-sodium fumigation, NPK fertilizer or mancozeb alone applied as soil treatment did not increase apple tree growth on cherry orchard soil over 3 yr. The consistent performance of strain EBW4 of B. subtilis for 3 yr suggests that this bacterium has the potential to be used as a biological treatment for planting apple trees in soil previously planted with cherry in the Kootenay Valley of British Columbia.