Problem type: Disease
Name of problem: Raspberry spur blight
Plant name(s): Raspberry (red and purple)
Symptoms / Characteristics:
Purple or dark brown lesions occur on the canes directly below the points of leaf attachment. Eventually these spots may extend to buds and leaf stems. Lower leaves turn yellow and drop prematurely, leaving the petiole attached. Infected leaves often exhibit brown, V-shaped lesions with yellow margins. Darkened tissue turns grey or silver in the fall. The bark dries out and splits lengthwise. At this point, small black fungal bodies may be visible.
Raspberry spur blight is a fungal disease caused by Didymella aplanata. Spur blight and cane blight often occur simultaneously, making diagnosis difficult. Raspberry cane blight is caused by a different fungus (Leptosphaeria coniothyrium) and, although the symptoms differ, the control methods are similar.
Control / Preventions:
Avoid wounding the canes during pruning and harvesting. Restrict pruning to periods of dry weather. Remove and destroy infected canes throughout the growing season and remove fruiting canes after harvest. Promoting good air circulation reduces disease incidence. This involves regular weeding, pruning, thinning and the removal of fruited canes. Avoid dense plantings and excess irrigation, as warm and wet conditions favour the development and spread of the disease. Avoid excess irrigation. The fungus invades both healthy and damaged tissue. Avoid applying excess nitrogen fertilizer as this promotes the growth of vulnerable succulent tissue, ideal for fungal invasion. Resistant varieties are available. There are several registered fungicidal controls.