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 esta blished that the root-dip application of strain EBW4 of Bacillus subti lis alone was effective in increasing the growth of apple trees plante d in old cherry orchard soil that was conducive for replant disease. T he response was measured by increases in cross-sectional trunk area an d shoot height of Jonagold apple trees on (Malus domestica Borkh.) M.9 rootstock. Strain EBW4 of B. subtilis applied as root-dip in combinat ion with metham-sodium fumigation, peat, or NPK fertilization, was als o effective in promoting growth of apple trees but not as consistently as when it was applied alone. Metham-sodium fumigation, NPK fertilize r or mancozeb alone applied as soil treatment did not increase apple t ree growth on cherry orchard soil over 3 yr. The consistent performanc e 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 ap ple trees in soil previously planted with cherry in the Kootenay Valle y of British Columbia.