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Spots or blotches on blueberry stems or branches:

Canker diseases

Fusicoccum putrefaciens and Phomopsis vaccinii

• Reddish-brown, target like cankers can be found on infected branches
• Cankers are often low on the branch and near a leaf scar
• Cankers enlarge each year until they girdle and kill the stem
• In summer, leaves on infected branches, wilt and turn reddish-brown
• Small black bumps can be found around cankers and on dead branches

More information on Canker diseases

Anthracnose

• Salmon to orange colored sticky spore masses develop on infected berries and stems when wet
• Infected twigs/canes have dark brown lesions with raised bumps arranged in concentric circles
• Reddish-brown round to irregular spots on leaves
• Berries become soft and wrinkled from the blossom end

Botrytis Blight/Gray Mold

Botrytis cinerea

• Twigs turn brownish-black and become gray
• Infected blossoms turn brown and become covered with a fuzzy gray mold
• Berries are covered with a fuzzy gray mold
• Leaves have brown, irregular lesions and may become distorted

More information on Botrytis Blight/Gray Mold

Unusual growth on stem or branches:

Crown Gall

Agrobacterium tumefaciens

• Galls (tumor-like overgrowth) occur on roots, where the stem meets the soil and occasionally higher on stems
• Young galls are soft, light green in color, with no bark
• Older galls are brown to black and are hard
• Severely infected plants may be stunted
• Severely infected plants should be removed and destroyed

More information on Crown Gall

Witches Broom

Pucciniastrum goeppertianum

• Broom-like clusters of swollen reddish-brown stems and small leaves develop in the plant
• Young stems within brooms are initially yellow or reddish, but later become brown and shiny, and, eventually, dry and cracked
• Most common on blueberries in northern Minnesota planted near fir trees
• Will cause needle yellowing and loss in nearby fir trees
• Infected blueberry plants should be removed and destroyed

More information on Blueberry witches broom

Source: University of Minnesota Extension