Northwest berry Foundation

Management Detail

Phomopsis Twig Blight

in Blueberries

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Latin name: Phomopsis vaccinii

Description:

Reason for Concern:
1) This canker disease causes dieback of flowers, twigs, and shoots, as well as fruit rot.
2) Bushes that have been weakened by other factors are usually more prone to infection.
3) Frost injury to the base of plants or shoots may result in girdling cankers.
4) This disease is most severe in seasons following winters with mild spells interspersed with cold weather.
5) Periods of hot, dry weather during the growing season may predispose plants to this disease.

Identification/Symptoms:
The primary symptom is a blighting of 1-year-old woody stems that have flower buds. Visible symptoms occur soon after the flower buds reach the green-tip stage first on small twigs and then larger branches. Individual buds turn brown and die, followed by browning and death of the bark around the bud as the fungus spreads from the blighted bud into the twig, spreading until most or all of the flower buds on an individual twig are killed. There it stops, not progressing further down the stem to infect older wood. New infections occur continually as buds open, flower, and produce fruit. Small branches, usually about 2" to 6" long, may wilt suddenly and die. Leaves turn reddish and remain attached to the stem. Infected fruit are soft, often split, and leak juice. Twig blight symptoms are sometimes confused with botrytis fruit rot, fruit rot is characterized by a gray, fuzzy mold on the affected plant part, and there is no dark brown discoloration of the twig.Girding cankers on 1-year-old stems become obvious by early summer and continue to progress downward, eventually encircling the entire shoot. Cankers begin as elongated brownish areas and can become up to 4" long. They can be at ground level up to several feet above the ground. On older stems, the cankers become grayish and flattened and grow up to 8" long. Side branches that become encompassed by the canker will wilt in hot weather. The cankers become covered with tiny black dots: the fungal spore-producing structures. As canes mature, they become girdled by the diseased lesions.

Links:

Scouting:

  • Infection occurs through flower buds and wounds from budbreak to bloom, causing twig, flower, or shoot dieback.
  • It can also enter the plant through pruning wounds or frost cracks and cause girdling cankers.
  • Not common in the Northwest.

 
Cultural Controls:

  • Avoid wounding or injuring plants.

 

For information about chemical controls, check with our Pesticide Guide.

images


photo from Michigan State University


photo from Michigan State University

 

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