Latin name: (no Latin name)
Reason for Concern:
1) This virus is common and can be confused with scorch virus.
2) Plants may exhibit shock symptoms for 1 to 3 years but then produce a normal fruit yield. Even though symptom-free, the plant still has the virus and serves as a source of inoculum for further spread.
Blossoms are blighted in spring when flowers are just about to open. Infected young leaves wilt and develop blackened streaks down the center vein, and can blight, turning orange. The entire bush may be blighted, but more often only a part of the branches show symptoms. These symptoms represent the plants "shock reaction" to infection. At this stage, scorch virus and shock virus look the same. Leaves that remain green may develop visible, red ringspots on both sides of the leaf which can also be noticed on the leaves that appear the following season. Blighted blossoms and leaves drop, defoliating bushes by early summer. A second flush of leaves is produced. Infected bushes appear normal by late summer, although there will be little fruit. Berkeley, Bluegold, Earliblue, Duke, Pemberton, Rancocas and Bluetta are very susceptible. Symptoms occur for 1 to 3 years and then the plant recovers. A good crop can be produced in well-managed fields although recovered plants are still infected with the virus. Pollen produced from these plants is contaminated with the virus. Thus, the virus can spread to nearby healthy bushes during pollination.
The virus is dispersed by infected pollen carried by bees or by infected planting stock. It spreads rapidly in a radial pattern from the infection focus. 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.
- Flowers and young vegetative leaf shoots suddenly die when flowers are just about to open (shock reaction).
- The entire bush may be blighted but, more commonly, only a portion of the branches will show symptoms.
- Blighted tissues drop; as the season progresses a second flush of leaves is produced.
- By mid-summer, affected plants look normal except they produce little fruit.
- Plants may exhibit shock symptoms for one to three years and may be symptom-free thereafter, producing a normal fruit yield.
- To correctly identify the virus causing the symptoms, contact your local extension office to arrange for sending in a sample to be tested.
- As shock virus is spread via pollination there are few controls to stop the virus from entering a field, and there is little research done to determine the patterns of infection. Since plants fully recover, shock virus economic damage is considered minimal.
- Go to (Oregon State University Online Guide) for a description of other blueberry viruses.