Aphid vectors of plant viruses migrating in North-West Italy.

The flight activity of aphid species known a s vectors of barley yellow dwarf virus (BYDV) and plum pox virus (PPV) was studied in North-West Italy from 1982 t o 1987. The winged, migrating f orms were captured daily with a suction trap of the Rothamsted Insect Survey type working in Carmagnola, about 30 km South of Torino, a t 12.20 m from soil level. The following species were studied: Anoecia corni (1), Hyalopterus pruni, Metopolophium albidum, M. dirhodum, M. festucae, Rhopalosiphum insertum (2), R. maidis ( 3 ) , R. padi (4), R. poae, Schizaphis graminum, Sipha elegans, Sitobion avenae (5) and S. fragariae, all vectors of BYDV; M. persicae (6), vector of both BYDV and PPV; Brachycaudus helichrysi , and Phorodon humuli, vectors of PPV. The number of individuals of each species captured is reported as weekly sums ( referring t o "standard" weeks), together with weekly rainfall and mean temperature. Some characteristic patterns of migration are compared for each species in d i f f e r e n t years. In 1987 the autumn catches of six species of BYDV-vector species accounted for over 99 % of the total of BYDV vectors, thus confirming our previous finding that the patterns of auturnn migration of all BYDV vector species can be adequately estimated by counting only the species listed above as (1) t o (6).