Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Blueberry -- Shock
 
Cause: The Blueberry shock virus (BSIV) which is pollenborne. Transmission occurs when pollinators, especially foraging honeybees, transfer infected pollen to flowers on healthy plants. All cultivars are susceptible. Once the disease appears in a field, it cannot be eliminated by removing and destroying plants with symptoms. Plants that have recovered from the symptoms appear to produce a full crop, but these plants can continue to serve as an inoculum source for nearby plants and for any new plantings. The disease has been confirmed in Oregon, Washington and British Columbia.
Symptoms: Flowers and young vegetative leaf shoots suddenly die in spring when flowers are just about to open. The entire bush may be blighted, but more often only a part of the branches show symptoms. These symptoms represent the plant's "shock reaction" to infection. Blighted tissues drop; as the season progresses, a second flush of leaves is produced. By late summer, affected plants look normal except they produce little fruit. Leaves that do not blight in spring may show thin red ringspots which are visible on both sides of the leaf. Plants may exhibit the shock reaction for 1 to 3 years and may be symptom-free there after although they still carry the virus.

Note the green stems but with blighted flowers. The healthy comparison stem is in the center of the picture.

The bush without leaves on the right is showing shock for the first time. Other plants in the area appear healthy.

Leaf spots are seen when bushes recover and grow new foliage even the year after inital symptoms are observed.

Bud on the left are healthy but buds on the right have died due to Blueberry shock virus. Sometimes you can find secondary infection by Pseudomonas in these dead buds.
 
Cultural control:

  1. Use certified planting stock for new plantings.
  2. Do not establish new fields adjacent to infected fields.
  3. Maintain good cultural care of infected plants while they are going through seasons with the shock reaction.
  4. For small plantings, let the disease run its course. In larger plantings, rogue plants only if infected ones are confined to a small area; otherwise let the disease run its course.
Notes: This disease has a medium risk rating under Agriculture and Agri-Food Canada's Plant Health Risk Assessment for Vaccinium plants and cuttings from the continental United States. There may be a requirement for testing propagation material bound for British Columbia to ensure it is virus-free.
References:
Bristow, P. R. and Martin, R. R. 1999. Transmission and role of honeybees in field spread of blueberry shock ilarvirus, a pollen-borne virus of highbush blueberry. Phytopathology 89:124-130.
Content edited by: Jay W. Pscheidt on January 1, 2009
 
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