Spur blight (Didymella applanata) is a dangerous fungal disease of blackberry

Spur blight (Didymella applanata) is a fungal disease of blackberry. The disease is caused by a fungus Mycosphaerella rubina. 
The winter spores are developed during the fall and early spring in the little black pustules. These spores remain immature over winter, but mature early in the spring. They are discharged in the early part of May and, falling on the young shoots, start a new infection. The summer spores bring about infection later in the season. 
The first appearance of the disease is a brown or purplish-brown discoloration on the young canes just below the leaf stems. This appears... read more

This disease affects flowers and buds on plants, anthers are swollen, brown, and do not shed pollen

Caused by a fungus Hapalosphaeria deformans. This disease affects Boysenberry, Marion, Evergreen Thornless, and other cultivars with wild trailing blackberry in parents. The disease is severe in some plantings, severity varies markedly from year to year. Rain splashes spores from infected flowers to axillary buds of primocanes during bloom. The infection process occurs in summer.
Stamens of infected flowers are flattened against the petals instead of in an upright ring. Anthers are swollen, brown, and do not shed pollen. Since sporulation occurs before the flower opens, the flower has a white,... read more

This article describes the most important reasons causing blackberry diseases

The most part of diseases of blackberry plants is appearing due to bacteria and fungi activity. These microorganisms are living on the leaves and canes of the different plants, destroying, modifying plant and using it's resources.
Bacteria are ultral small one-celled microorganism, which reproduces very rapidly by a simple splitting into two cells. Each of these two cells soon grows up to the size of parent cell. They penetrates into tissues of the plants and causes different diseased conditions, for example - rotting and wilting. The some part of bacterial diseases can be cured.
Fungi are... read more

Very destructive fungal disease, poor growth and failed to set fruit as well as canes and leaves symptoms

Verticillium Wilt can be easily widespread and extremely dangerous. While raspberries and hybrid-berries are more susceptible to the disease, blackberries also are attacked by the pathogen but are not inclined to wilting. Verticillium Wilt is caused by Verticillium dahliae and Verticillium albo-atrum, a fungal plant pathogens.
These pathogens can exist in the soil prior to planting, may be brought in on planting stock, or may move with the wind. The pathogens can survive either in plant dead cuttings or free in the soil. The fungus enters the roots through breaks or wounds and moves into the... read more