Black Raspberry Streak in Home Fruit Plantings

Inconspicuous purple streaks less than 1 inch long form during warm periods on the lower part of infected canes. Infected plants usually are vigorous, sometimes with no symptoms of virus infection.
Black Raspberry Streak in Home Fruit Plantings - Articles

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The fruit, however, display diagnostic characteristics--they lack a glossy appearance, have drupelets that ripen unevenly, and are sometimes small, blotchy, and seedy. The vector of this virus is not known.

This virus is very unevenly distributed in plants, which makes detection difficult. Use of planting stock from virus-free indexed mother plants and isolation from plants that could be sources of this virus are recommended control measures.