INFECTIVITY OF CACOPSYLLA PICTA (SYN. CACOPSYLLA COSTALIS), VECTOR OF 'CANDIDATUS PHYTOPLASMA MALI' IN NORTH EAST ITALY

The recent council order on obligatory measures for the control of apple proliferation in Italy underlines the importance of vector control. For this reason the epidemiology of the disease was studied by focusing on the life cycle and the infectivity of the vector Cacopsylla picta. The proportion of both phytoplasma positive and inoculative insects was determined for both overwintering adults that would return to colonise apple trees in spring and for the springtime generation, hatched at the beginning of summer. The psyllids, collected in an area highly infected by apple proliferation, were split into groups of 3, 5, 10 and 50 individuals; they were tested by PCR for the presence of ‘Candidatus Phytoplasma mali’ or used for transmission trials on apple test plants. We showed that in spring, when the vectors moved to apple trees from shelter plants, they were infective. Part of the springtime generation colonising apple trees, after the acquisition of infectivity, completed the latency period and transmitted phytoplasma. Results showed that the risk of natural transmission of ‘Ca. Phytoplasma mali’ by C. picta within orchards is high during the entire period when the vector is present. These results are significant with regards to apple proliferation prevention strategies such as vector control.