The effects of the environment, especially those of temperature, on the susceptibility of young canes of red raspberry cv. Malling Jewel, to wound inoculation with D. applanata in late July, were examined. Inoculation of their internodes showed that canes grown in spring in an unheated glasshouse were more susceptible to infection and provided a better substrate for sporulation than those grown in cooler conditions outside. The axillary buds were smallest and lateral shoot failure was most severe following inoculation of petioles of canes grown under cool spring conditions and maintained at relatively high temperatures in August and September.
In British Columbia most canes of susceptible cultivars were naturally infected from soil level to above heading height. Buds at infected nodes were smaller, fewer lateral shoots emerged and the number of flowers per infected cane node less than at lesion-free nodes in the cropping region of canes. The results are discussed in relation to D. applanata infection of canes in Scotland where a cool spring climate is not so conducive to spur blight as in British Columbia.