Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Blueberry -- Twig Blight
 
Cause: Phomopsis vaccinii, a fungus that overwinters in infected plant debris. In the spring, spores are dispersed from fruiting bodies (pycnidia) embedded in diseased tissue by rain splash and irrigation water. Infection occurs through flower buds from budbreak to bloom. The disease spreads from flowers into shoots and twigs. The fungus can also infect through injuries such as pruning wounds, frost cracks and herbicide injury and produces girdling cankers. Not common in the Pacific Northwest.
Symptoms: Dieback of flowers, twigs, and shoots. Frost injury to the base of plants or shoots may result in girdling cankers.
Cultural control:

  1. Purchase healthy planting material and/or do not use plants with injured branches.
  2. Prune out, remove, and destroy infected and dead branches.
  3. Avoid wounding or injuring plants.
Chemical control:

  1. Abound at 6 to 15.5 fl oz/A. Do not apply more than 2 sequential applications or more than 3 applications per year. May be applied on the day of harvest. 4-hr reentry.
  2. Cabrio EG at 14 oz/A. Do not use more than 2 sequential applications or more than 4 applications per year. May be used at harvest. 24-hr reentry.
  3. Captan 80 WDG at 1.25 to 3.1 lb/A plus spreader sticker. May be applied up to day of harvest. 72-hr reentry.
  4. Indar 2F at 6 fl oz/A plus a wetting agent. Do not use within 30 days of harvest. 12-hr reentry.
  5. Pristine at 18.5 to 23 oz/A. Do not use more than 2 consecutive applications or more than 4 times/year. Can be used day of harvest. 12-hr reentry.
  6. Switch 62.5 WG at 11 to 14 oz/A. May be used up to and including the day of harvest. Do not apply more than twice sequentially or use more than 56 oz/A/season. 12-hr reentry.
References:
Parker, P.E. and D.C. Ramsdell. 1977. Epidemiology and chemical control of Phomopsis canker of highbush blueberry. Phytopathology 67:1481-1484.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
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