WSU Whatcom County Extension

Integrated Pest Management for Blueberries

Blueberry Shock Ilarvirus

Disease Pests

 

Shock

Symptoms

Blueberry shock virus (BSIV) is widely spread in blueberry production areas. During bloom, bushes infected with shock virus will suffer from loss of foliage and blossoms resulting in yield loss. New growth of infected plants will be evident at the time of the second flush.  These plants will resume full production in the following season.

 

Life History

Shock virus is pollen borne and is transmitted by pollinators between plants. The virus can spread quickly once established in the field. Symptoms begin to appear just prior to bloom and can continue to develop during bloom. Affected new tissue appears black and older foliage will turn orange. Foliage and developing flowers will wither, eventually falling off by harvest. Affected bushes will flush with new foliage by harvest but little fruit will be produced for that season. Shock can affect an entire bush or just parts of the bush. In portions of the bush that are affected, expect to see the other sections to show symptoms in the up coming years. Once a bush is infected, it will continue to test positive but be symptomless after one to four years. Research has shown that yields are not significantly impacted in recovered bushes.

 

Monitoring

In spring, just prior to bloom, regularly monitor for shock and scorch symptoms. Blueberry shock virus symptoms are identical to blueberry scorch virus.  Test suspicious plants immediately.  Follow the Sampling Guidelines for Blueberry Scorch Virus (pdf) for testing plant samples.   Make sure to label sampled plants with an identification code used in the virus testing.  This will enable you to make a decision on the fate of the potentially infected plant.  Management options vary between scorch and shock, so correct identification is crucial. 

 

Thresholds and Management

Plants with shock virus fully recover.  Once identified as shock (and not scorch), plants should remain in the field.

Management practices used for scorch virus, such as plant removal, are not effective once blueberry shock virus is established in a field.  Promote plant health in infected fields. Fields that are isolated from other blueberry fields may be protected from blueberry shock virus. Purchase virus free plant stock to avoid infection. Use pollinators that originate from non-blueberry fields.

 

Resources

Oregon State University Extension, An Online Guide to Plant Disease Control, Shock Virus
http://plant-disease.ippc.orst.edu/disease.cfm?RecordID=188

Michigan State University, Blueberry Facts, Shock Virus
http://www.blueberries.msu.edu/shock.htm

 

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WSU Whatcom County Extension • 1000 N. Forest St., Bellingham, WA 98225 • 360-676-6736 • whatcom@wsu.edu