In a greenhouse trial, 4 petioles on young canes of 7 Rubus idaeus cultivars were inoculated with 13 pathogen isolates. Axillary buds at treated nodes were shorter and emergence of lateral shoots was less than at uninoculated nodes in all cultivars. The length of buds was significantly affected by cv. and position of buds on the canes. In cv. Chilcotin there was a 39.7% reduction in length in inoculated buds. There were significant cv. X isolate interactions, vs. 18% in Meeker. This was confirmed by joint regression analysis of bud and lesion lengths in 8 cultivars grown in the field and tested with 14 isolates. No discontinuous variation in disease expression was found.