This is a disease peculiar to wild and cultivated blackberries. It is found in Europe and in eastern North America. In the northern United States where it occurs there is no need for alarm on account of its late fall appearance. However, it may assume a more important role south of New York State.
Plants in sandy soil are said to be more affected. Rust pustules are produced on the canes the last of May or in June, or about blossoming time. These are bright, lemon-yellow in color, and measure from one-eighth to one-half an inch in diameter. They are usually found on the stem near the ground. Later the leaves are affected, the disease first appearing on the lower surface of the leaves of fruiting canes, then on those leaves attached to the new canes. The fruit - stalks and flowers are also rusted.
The general appearance of the disease has given rise to the names yellow Late Rust, white rust, cane rust and Late Rust.
Little is known of the seasonal cycle of the causal fungus, Kuehneola albida, and of its control.
Wilson, G. W. Rusts of blackberries, dewberries, and raspberries. Late rust. Cane rust. North Carolina Agr. Exp. Sta. Rept. 35: 58 - 61. 1912.
Stone, G. E., and Smith, R. E. A late rust of the blackberry (Chry - somyxa albida, Kuhn). Massachusetts (Hatch) Agr. Exp. Sta. Rept. 9: 74. 1897.
Strelin, S. Beitrage zur Biologie und Morphologie der Kuehneola albida (Kuhn) Magn. und Uredo Mulleri Sehroet. Mycol. Centbl. 1:131 - 137. 1912.
Blue Stem is better known on raspberries than on blackberries. Little trouble has been reported from this disease on the latter fruit. It is a Pacific Coast disease at present. (See Raspberry, page 416.)