Evaluation of Biological and Chemical Treatments for Control of Crown Gall on Young Apple Trees in the Kootenay Valley of British Columbia

Field trials at Creston in 1988, 1989, and 1990 on silty loam soil naturally infested with Agrobacterium tumefaciens showed that Agrobacterium radiobacter strain K84 did not control crown gall on young Antonovka apple trees when apphed as a root-dip treatment. Copper oxychloride applied as a root-dip treatment at 2.5 and 5.0 g ai/1 and sewage sludge applied at 260 g per tree as broadcast were effective in reducing crown gall infection but these treatments were toxic to young apple trees in 1989. Lower rates of copper oxychloride, 0.3, 0.6 and 0.9 g ai/1, and sewage sludge at 130 g per tree, did not control crown gall in the 1990 field trial. The biological treatment with the strain AB8 of Bacillus subtilis applied as a root-dip effectively controlled crown gall and was not phytotoxic to young Antonovka apple trees. These results suggest that strain AB8 of B. subtilis has the potential to control crown gall on young apple trees under field conditions.