The effect of temperature on the response of canes of red raspberry cv. Mailing Jewel to infection by Didymella applanata

SUMMARY A single population of container‐grown red raspberry plants cv. Mailing Jewel was divided and grown in two environments prior to wound inoculating young canes with Didymella applanata in late July. The plants were then sub‐divided and held in one of three contrasting post‐inoculation environments. Various assessments were made to examine the effect on spur blight of the different environmental treatments. Inoculation of internodes showed that D. applanta produced longer lesions and more pseudothecia on canes grown in spring in an unheated glasshouse than on canes grown outside, but post‐inoculation conditions had little effect on these aspects of disease. Petiole inoculations showed that dwarfing of axillary buds in the first season and lateral shoot failure in the year after infection were most serious on canes grown outside in spring but held at relatively high temperatures in August and September after inoculation. The results indicate that spur blight may have the potential to cause higher yield losses in areas with warmer spring and autumn conditions than those usually experienced in north‐east Scotland.