Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Blueberry (Vaccinium corymbosum) -- Alternaria Fruit Rot
 
Cause: Alternaria spp., fungi. Although not as common as ripe rot, this disease has caused severe losses in some Oregon fields. Infections can occur any time between late bloom through fruit maturity. Infections remain quiescent (latent) until fruit ripens. The disease often is not seen in the field but develops in storage or in transit to market.
Symptoms: As fruit ripens, the first symptom is a shriveling or caving-in of the side of the berry. This deformity is generally located near the flower end of the berry. The damaged part may be covered with a blackish or dark greenish mass of spores that gives the surface of the berry a dull cast. Although berries may be dry in the field, the rot can become watery when harvested fruit is stored. Infected berries also tend to break open easily.
Cultural control:

  1. Harvest promptly to prevent overripe fruit.
  2. Cool berries rapidly after harvest.
  3. Avoid wounding or bruising fruit during harvest.
Chemical control: Spray after full bloom when berries are developing. Bloom applications have not been very effective.

  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 two (2) sequential applications or more than four (4) applications per year. May be used on the day of harvest. 24-hr reentry.
  3. Captan 80 WDG at 1.25 to 3.1 lb/A. May be applied up to day of harvest. Moderate control ranking. 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.
  7. Ziram 76 DF at 3 lb/A. Do not apply after 3 weeks from full bloom. Moderate control ranking. 48-hr reentry.
Notes: Although Bravo products are registered on blueberry, they have not been shown effective against this disease and cannot be applied after early bloom.
Biological control:
  1. Serenade MAX at 1 to 3 lb/A. Active ingredient is a protein from Bacillus subtilis strain QST 713. Efficacy in the Pacific Northwest is unknown. 4-hr reentry.
References:
Bristow, P. R. and Windon, G. E. 1998. Epidemiology of Alternaria fruit rot in the Pacific Northwest. pp. 176-179. In Cline, W. O. and Ballington, J. R. (eds.). Proc. 8th North American Blueberry Research and Extension Workers Conf. May 27-29, 1998. Wilmington, NC. 293 pp.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
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