Pest risk assessment for apple proliferation phytoplasma ('Candidatus Phytoplasma mali')

VKM’s Panel on Plant Health gives the following main conclusions of the risk assessment: 1) The overall probability of entry is considered as very likely, with a low level of uncertainty. Plants for planting, scions, budwood and rootstocks are the main pathways for AP. Insect vectors are only of concern regarding local spread of AP. 2) The overall probability of establishment is considered as very likely, with a low level of uncertainty. Apple and some other species of Malus are the main hosts of the pest, and the number of host plant species is low. However, host plants are widespread and abundant in the PRA area. The vector Cacopsylla melanoneura occurs in parts of the PRA area. The climatic conditions are considered as suitable for AP because there have already been restricted outbreaks in Norway. Establishment is not restrained by competitors or natural enemies. Existing cultural or management practices are ineffective to prevent establishment. 3) AP may easily be spread by plants for planting, rootstocks, scions, budwood, and psyllid vectors. Plant materials are easily and rapidly spread within the whole PRA-area, and consequently represent a considerable risk for spread of the disease. Psyllid vectors and root bridges may be important for rapid local spread; 4) There is a high probability that AP may cause extensive economic damage in fruit orchards in the country. Apple is commonly grown in private gardens all over the southern part of Norway. In the central and northern part of Norway apple growing is restricted because of lower average temperatures. Commercial growing on a large scale is mainly restricted to some areas in the counties of Rogaland, Hordaland, Sogn og Fjordane, and Møre og Romsdal in Western Norway, and the counties of Buskerud, Telemark and Hedmark in Eastern Norway. Consequently these areas will be at most risk economically for AP to establish in Norway.
NO; en; vkm@vkm.no