Situation of cherry little cherry 'closterovirus' in British Columbia, Canada
Cherry little cherry 'closterovirus' was first identified in British Columbia, Canada in 1933, at Willow Point in the West Kootenay's. The disease then spread in the Kootenay Valley, infesting virtually all cherry orchards and production dropped from 680 t in 1947 to 68 t in 1979. The disease appeared in the Okanagan Valley in 1969, and major outbreaks were observed in 1973 and 1977. In 1947, 'the little cherry control regulation' was set up under the authority of the British Columbia Plant Protection Act, to limit the spread of the disease (and in particular to protect at that time the Okanagan cherry industry). This regulation provides for a 'little cherry control area' which now includes: the Okanagan and Similkameen valleys (51st parallel north, 119th meridian east, 121st meridian west, Canada/US border south); the Kootenay region (Creston area). Surveys are carried out in this area and control programmes include the following aspects: use of virus-free planting material; elimination of infected trees, prohibition to grow or import ornamental flowering Japanese cherries (which are symptomless carriers of the pathogen); elimination of cherry seedlings in and near orchards, as well as wild bitter cherry (P. emarginata); control of the insect vector (apple mealy bug: Phenacoccus aceris). During surveys, trees are visually inspected and samples are collected for indexing on woody indicators (new diagnostic techniques are under development).
In the Okanagan valley, results were the following in 1995-96: 26 trees were found infested and destroyed in 1995, and 7 in 1996. However, a thorough survey has not been done in this region for many years. Disease is known to be established throughout the central Okanagan (Pencticton to Oyama) and continues to be found in new locations. The area south of Pencticton has not been surveyed during the last 10 years.
Surveys done in the Creston, Erickson, Wyndell, Canyon and Lister areas, showed the presence of the disease. In Creston: 80 trees were found infected in 1995 and 31 in 1996. However, in the Creston area the control programme has eliminated enough infected trees to allow considerable planting of new orchards (over 41 ha) and production which had fell to 27 t in the 1970s, reached 115 t in 1995.
It is stressed that surveys and control programmes have helped to keep incidence low in commercial orchards but have not eradicated the disease.
Web site of the Ministry of Agriculture and Food, British Columbia, Canada.