Caneberry spur blight

Signs. In the late summer, the bark of infected areas split and the lesions produce fruiting bodies called pycnidia. Pycnidia appear as small black dots to the naked eye and can been seen as flask-shaped structures under a microscope. Perithecia another fruiting body, forms after the pycnidia. Perithecia appear as medium, black, erupting dots. In the spring, spur blight can be mistaken for winter injury therefore it is important to scout for these signs in September to assess the potential damage that will be done in the following season. 
Symptoms. Infection generally occurs in the late spring when the environment is wet and optimal for fungus to proliferate. Symptoms do not become visible until mid to late summer. Visible symptoms include purple and brown expansive lesions appearing below buds, leaves and the lower portion of the stem. Leaflets that are infected have wedge-shaped brown patches. Infected leaflets may fall, leaving only the petiole and canes behind. During the next season, branch growth from diseased canes will often be weak and wilted.
Disease Cycle. The raspberry spur blight fungus spreads through the pyciospores that are released from the pycnidia. The spores are released and infect other raspberry plants with the help of rain through open wounds or natural openings. The fungus will then spread throughout the plant and will live in lesions during the winter to survive. After winter there are two spore types that are formed pycniospores and ascospores. The pycniospores come from conidia and the ascospores come from the perithecia that was formed. Both of these spores will spread through rainfall onto new plants and start the process over again.