Mycelial inoculation of canes proved a useful method for assessing R. material for resistance. When canes were inoculated in summer resistant genotypes developed relatively small lesions which produced a few small sclerotia in the following spring. The size of lesions in autumn generally provided the best discrimination between genotypes. Very strong resistance was found in several spp., of which R. pileatus and R. occidentalis are the most useful for breeding; hybrids of raspberry with these spp. or R. crataegifolius also had strong resistance. The resistance shown by a derivative of red raspberry cv. Chief was less strong, as was the resistance conferred by gene H, which determines cane pubescence.