Blueberry red ringspot observations and findings in North Carolina.
Observation of suspected blueberry red ringspot virus (BRRV) prompted a survey of the 50-acre NCSU Ideal Tract blueberry farm, and of commercial farms in surrounding counties. Polymerase chain reaction (PCR) testing with red ringspot-specific primers was used to confirm the presence of the virus. Over 18 000 plants were surveyed visually, with PCR used for backup confirmation. The virus was detected primarily in highbush and southern highbush (Vaccinium corymbosum) seedlings, selections and cultivars. Incidence was low. Spread occurred primarily by propagation, but rare, widely scattered infections in older fields suggested an infrequent or inefficient winged vector. Hundreds of rabbiteye (V. virgatum, syn. V. ashei) bushes were also surveyed; symptoms were not observed on any rabbiteye cultivars, and were observed but not confirmed on rabbiteye seedlings. Samples from rabbiteye cv. 'Columbus' were negative in PCR testing. Symptoms were observed, and confirmed by PCR, on highbush and southern highbush from three surrounding counties, including wild or feral blueberries near commercial fields. Symptoms were first seen in early June, became progressively more noticeable through August, and included red rings on leaves, stems and fruit. Scattered to numerous red rings (3-6 mm) with green or pale green centres were the most frequent symptom on leaves, usually visible only on the upper leaf surface. Larger (5-15 mm) red rings or spots were visible on stems of the current season's growth. Most cultivars/clones had few or no fruit symptoms; only 'Ozarkblue' produced distorted, unmarketable fruit on infected bushes. Some infected seedlings and selections appeared to be stunted. The virus has also been reported from Georgia; in this study, southern highbush cultivars 'Star' and 'Misty', reportedly from a Georgia nursery source, were symptomatic and tested positive for the virus. Studies beginning in 2008 will assess possible seed transmission, possible vectors, and determine incidence and severity in southeastern USA.