Effects of spur blight (Didymella applanata) and premature defoliation on axillary buds and lateral shoots of red raspberry

Nodal lesions typical of natural infections of Didymella applanata were produced on young raspberry canes when wounded petioles were inoculated with mycelium. The buds which developed in the axils of these inoculated petioles were smaller and less likely to produce lateral shoots than those in the axils of delaminated or undamaged petioles, but only when the petioles were inoculated in the field before the end of July. This effect was more pronounced in cv. Mailing Jewel than in cv. Glen Clova which suggests that the latter is more tolerant of D. applanata. Sprays to control D. applanata in the cropping region of canes will probably be effective in Scotland only if applied before the end of July.