Q How do I recognise raspberry spur blight?
A Spur blight starts on new canes, appearing in August as areas of purple discolouration, often around a leaf bud. These change colour, first to brown, then black, then whitish. In winter they are less distinct but become dotted with tiny black fruiting bodies.
The areas of damage also enlarge, affecting lengths of cane up to 10cm long. If the damage girdles the cane, the top may die back. Next year, affected buds may not develop, or they may produce shoots which just die back.
Caption: Spur blight affects lengths of cane up to 10cm long
Q Tell me more about raspberry spur blight.
A The disease is caused by the fungus Didymella applanata. By killing buds it reduces fruit production the following year. It also affects loganberries and hybrid berries, and occurs more in Scotland and the north.
Q How do I control raspberry spur blight?
A Affected canes can't be treated. Cut them out and burn them.
Q How can I prevent raspberry spur blight?
A Overcrowding encourages spur blight. Thin the new canes in autumn to 15cm apart on the training wires. In spring, follow the spray programme outlined for cane blight, starting when the canes are 15cm high.