Crumbly Berry, Raspberry Bushy Dwarf
Crumbly berry is the most common bramble virus in the Mid-Atlantic region. This is a red raspberry disease caused by the tomato ringspot virus and spread by the dagger nematode. Many plants that appear normal produce small fruit that fall apart when picked, which results from the failure of some of the drupelets to develop. Since this virus primarily acts on the vitality of pollen, poor pollen performance results in unfertilized seed and undeveloped seed, which result in undeveloped drupelets. This virus has a wide host range, including many weeds such as dandelion. Symptoms of this disease vary with raspberry variety. Yellow ringspots can be seen on the expanding leaves of new shoots that often will disappear in midsummer. The canes sometimes are stunted and plant vigor is reduced.
Plants are infected when infected pollen is transferred by pollinators or by wind. Infected plants can be found in the wild as well as in flowering plantings. New plantings located near infected plants frequently become infected within two or three flowering seasons.
Management can be especially difficult because this virus is pollen vectored. Wild brambles in the vicinity should be eliminated, but because pollinators can travel long distances, eliminating enough plants to eliminate the virus may not always be possible. Esta and Heritage seem to be resistant to this virus.