An outbreak of plum pox virus in Norway

Plum pox potyvirus (PPV) was detected in plum trees in Norway in 1998. This is the first known case of PPV in Norway. During the period 1998 - 2003 altogether 24,864 samples were tested. These samples represent approximately 60,000 trees, of which 638 trees (1%) were infected by PPV. PPV was found in 55 orchards and nurseries and in all areas with economically important plum production, except in the county of Telemark. The primary infection source has been the plum variety collection at Njos Research Station. Most probably, the first infected trees were introduced to Njos by import around 1970. Since then, PPV has slowly been spread by aphids through the variety collection and also into nuclear stock material at Njos. From Njos, infected scions have been spread to nurseries and commercial growers. In some orchards and nurseries, PPV has been spread by aphids. Most infections were detected in 'Mallard'. This cultivar develops leaf symptoms, but almost never fruit symptoms. The main plum cultivar of Norway, 'Victoria', hardly develops any leaf symptoms, but severe fruit symptoms. By the end of 2003, most areas with economic fruit production have been surveyed. These results give a good hope for eradication of PPV from commercial Norwegian plum production.