SCORCH AND SHOCK: EMERGING VIRUS DISEASES OF HIGHBUSH BLUEBERRY AND OTHER VACCINIUM SPECIES

Blueberry scorch virus (BlScV) was first characterized in 1988 and subsequently it was shown that Sheep Pen Hill Disease of blueberry in New Jersey was caused by a strain of BlScV. There was not much interest in the virus until the mid 1990’s when blueberry scorch disease became increasingly important in New Jersey. In 2000, BlScV was detected for the first time in British Columbia, Canada and has since been found to be widespread in blueberry plantings there. The virus can be transmitted by several different aphids under experimental conditions but the vector(s) that are important for transmission in the field are not known. In 2003, it was discovered that cranberry is a symptomless host for BlScV. It appears that there are significant biological differences between some strains of BlScV especially with respect to symptoms in many cultivars. The NW type strains do not produce visible symptoms in many cultivars, whereas the EC strains cause leaf and flower blighting in most cultivars other than ‘Jersey’. Blueberry shock virus (BlShV) was first reported in 1991 in Washington and Oregon and has continued to spread in Oregon, Washington and British Columbia since that time. It has not been reported from other blueberry production areas. It is pollen-borne and plants show a severe shock (dieback of flowers and leaves) reaction the first one or two years after infection but do not show any symptoms in subsequent years and the recovered plants produce a full crop. Other viruses of importance in blueberry include Tomato ringspot, Tobacco ringspot, Blueberry shoestring and Blueberry leaf mottle along with a few viruses of minor importance.