Tree Fruit & Grape News, May 2001

Little Cherry Survey Update

The 2000 Survey 

A total of 935 cherry trees were tested for Little Cherry Virus (LCV) during the 2000 survey. Samples were collected from late June through to the end of August from Creston, Penticton, Keremeos, Cawston, Oliver, Summerland, Naramata, Kelowna, Westbank, Peachland, Winfield, Oyama, and Vernon, with the heaviest sampling at Penticton and Creston. 

Summary of Results: 

• There were 102 positive samples, with 17 positives in Creston and 85 in the Okanagan 
• Overall, 10.9% of samples were positive 
• All Okanagan positives were in the Penticton area 
• 12.2% of Creston samples were positive 
• 16% of Penticton samples were positive 
• The percentage of positive infected samples collected in individual orchards ranged from 0 to 100%. One Penticton orchard with a long (30+ years) history of LCV infection was intensively surveyed. Each tree was sampled individually. 
  • 349 samples 
  • 38 positives (10.9%) 
  • Positive samples show a clustered pattern, indicating a slow rate of spread. 

Testing methodology 

The new ELISA test that was developed by D'Ann Rochon's lab at the Summerland Research Station was ready for field testing this summer. All survey samples were tested by ELISA with great success. All positives and additional random samples were double-checked by PCR. The results were in agreement for Okanagan samples, but there were discrepancies for many samples from Creston (positive by ELISA, but negative by PCR). Possible reasons for the discrepancies were investigated last fall. It was determined that the ELISA test is picking up an additional strain of LCV that was not picked up by the PCR test. There is no doubt that the additional strain is LCV. 

A Second Little Cherry Virus? 

Since switching to laboratory tests for LCV several years ago, it has been noted that we are no longer finding LCV in many Central and North Okanagan orchards where LCV was detected in the past by woody indexing. This raises the question of what we were finding in the woody indexing for these sites. If it is not LCV, it may be a different virus with similar symptoms. Preliminary research at AAFC Summerland by Mike Bernardy indicates that there may be a cherry virus in the North Okanagan that is similar to a German Little Cherry Virus. This virus is not closely related to the BC Little Cherry Virus, however it is also called "Little Cherry Virus" and has similar symptoms. Further research is needed to confirm this. Plans for 2001 The Okanagan-Kootenay Cherry Growers Association is currently pursuing funding for research into the causal agent of the North Okanagan little cherry disease and its distribution. It is anticipated that the project will proceed this summer under the direction of Mike Bernardy at AAFC, Summerland. Planning for the 2001 survey is also underway. The survey will concentrate on the Penticton and Creston areas. A minimum of 4000 trees will be tested if requested funding is secured. Samples will be tested using the new ELISA test. Current LCV regulations will be re-examined based on results of the 2001 survey. 

For more information, please contact 
Gayle Jesperson, Plant Pathologist, 
BCMAFF Kelowna.

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