Saturday, July 16, 2011

Scouting fields for blueberry red ringspot virus

Red rings on stems are diagnostic for BRRV
Blueberry Red Ringspot Virus (BRRV) is hard to see during most of the year, but becomes most visible in late summer and early fall. Symptoms include red rings on both stems and leaves. Circular blotches or pale spots may also be visible on ripening fruit, though yield is often not affected. The cultivar Ozarkblue in particular can have severely distorted berries.

Unlike fungal leaf spots, the rings caused by BRRV have green centers or pale centers, and usually do not show through to the underside of the leaf. Rabbiteye cultivars appear to be resistant to the virus, while highbush and southern highbush cultivars are more susceptible. Plants are infected for life, and cuttings taken from infected plants will also have the disease – so it is very important to scout fields that will be used for cuttings, and avoid or remove any suspicious plants before they are propagated. The vector (carrier) is not known, so the only control for this disease is to look for it in July-Sept and isolate or remove any infected bushes.

Spots on leaves are usually only visible on the upper surface. spots are red rings with green centers, unlike fungal leaf spots that have dead centers.
Infected plants may exhibit faint rings on ripening fruit that disappear when the fruit is fully blue.