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Cornell Fruit Resources: Berries

Resources for Commercial Berry Growers

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Blueberry Scouting

Pruning is a good time to scout for diseases in blueberries.

Make sure your pruning instruments are sanitized before you begin. Lysol is considered the best sanitizer for pruners, as it kills fungi, viruses, and bacteria, and doesn’t corrode metals. A solution of 10% bleach in 90% water is as effective as Lysol, but will corrode metals over time. Alcohol will work well to kill bacteria and viruses, but isn’t very effective against fungal spores.

After pruning, move canes away from the bushes. The best way to prevent diseases next year is to burn the canes. The wood ashes can be used as a fertilizer to provide K and micronutrients to a variety of crops.

Fusicoccum Canker:

Reddish spots on canes, often near the ground near a leaf scar. Spots 1 inch and larger develop a bull’s eye pattern. Read more about canker diseases at this link.

Young blueberry twig with orange fusicoccum canker. Canker is elongated oval form and has ringlike gradation in color intensity. Center is whitish-orange and outer edges are more rust-colored.
Fusicoccum canker with bull’s eye pattern. Cut this away.

Phomopsis canker and twig blight:

Phomopsis is a fast-moving fungus that usually enters blueberries through the tips of the canes. Cut away any cane tips that look black and dead. Watch for dead wood in pruning cuts. If possible, prune down until the wood is all green. Read more about canker diseases at this link.

Blueberry twig tip, brown and dead from phomosis infection. Lower down the cane the wood is again healthy and green.
Dead wood from Phomopsis tip blight. Cut this away.
Closeup of infected blueberry twig. Half of the cane is white and greenish surrounding the bark. Half of the cane is dark brown and appears dry beneath the bark.
This wood is infected by a fungal canker. Prune it down until all of the wood is green.

Stem gall wasp:

Stem galls can be caused by a small wasp that lays its eggs in the blueberry cane. If the stem galls do not have holes, remove and burn them. Read more about stem gall wasp at this link.

Dormant blueberry bush with several swellings roughly the size and shape of unshelled peanuts. Swellings are maroon in color and are located on twigs off of the main branch at varying heights.
Fresh stem galls. Remove and burn them.
Blueberry stem with three lumpy, egg-shaped galls. Two galls are bright red and shiny. One gall is lumpy, dull gray, and has multiple pin-sized holes.
Old blue-gray stem gall with exit holes. The wasps have already left from it.

Witches’ Broom

A rust fungus that dwells on white firs can cause witches’ brooms in blueberries, an unproductive overgrowth of branches. Cut affected canes out at the base of the plant. Read more about witches’ broom at this link.

Blueberry plant with broomlike, vertical cluster of thin twigs.
Witches’ broom growth on a blueberry bush.
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