Downy Mildew of caneberries

Downy mildew initially causes a light green to yellow discoloration on the upper blackberry or olallieberry leaf surface that eventually progresses to red and purple. Mature lesions are often angular and restricted by veins. White to gray spore masses also appear on the opposite side of lesions on the leaf underside, but they may be sparse and difficult to see.

Primocanes systemically infected by downy mildew are often stunted and have red streaks on the side of the cane that faces the sun, with reddish colored terminal leaves. Downy mildew infected fruit (dry berry) is dull in luster, lacking in turgidity, and dries out rapidly. Early infection of green fruit induces premature reddening, shriveling, and hardening. Fruit infection later in the season causes shriveling, drying, and the fruit splitting into two parts. Downy mildew infected pedicels are dry and red.