Cane Blight

This fungal disease appears only on fruiting canes, infection occurs on primocanes near the end of the growing season

Cane blight is caused by a fungus Leptosphaeria coniothyrium. On the canes spore chambers (pycnidia) are developed in which are produced enormous numbers of brown spores. These are exuded in such quantities as to form the smutty discoloration described. These pycnidia, formed on the fruiting canes, produce spores thruout the summer. In the meantime the new canes are growing up among the fruiting canes, and when these are headed back the fungus is given a chance to infect them at the wounded ends. Infection at other points on the new canes may occur during the summer, but it usually appears only where the canes are wounded or injured by insect puncture.
The fungus winters on the new canes as well as on the old fruiting ones. During the fall, on the diseased area of the fruiting canes the fungus develops hollow structures called perithecia, and in the spring other spores are formed in these. In addition, spores produced in the pycnidia live over winter or are formed in the old pycnidia m the spring. The fungus may live on the old canes at least four years after the canes have died. It is thus evident that there are numerous sources of infection in the spring and summer. The spores may be carried to the new growth by rain or mist or by insects, and here cause infection. Insects such as the tree cricket evidently play an important part in disseminating the spores. So far as is known, the fungus gains entrance only thru wounds on the canes, but these wounds are so common that there are usually plenty of chances for infection. It is also known that the berries may become infected and the fungus may grow down the pedicel and into the fruiting branches.
Owing to the fact that the fungus can winter on old and new canes and live for several years on the dead canes, methods of control have not met with much success. Fortunately, under ordinary conditions, the disease does little damage.
No fungicides have been identified for this purpose, but late-season applications of basic copper sulfate may be helpful. See user manual for directions.
Preventive measures consist in se-curing plants free from the disease, cutting out and burning old canes as soon as possible aft€r the fruit is harvested, and avoiding wounding the new canes.