The flight activity of 29 species of Macrosiphini, recorded over 6 years in a suction trap at Lincoln, is reported. Flight phenology and weed hosts of 20 species are described. The host plant relations of Myzus persicae (S ulzer) were examined. Mallow (Malva neglecta Wallred) and black nightshade (Solanum nigrum L.) were favoura~le hosts, while few M. persicae were found on whlte clover (Trifolium repens L.) or yarrow (Achillea millefolium L.). Aulacorthum solani Kaltenbach was the predominant aphid species on white clover and yarrow in the field, together with Myz~s ascalonicus Doncaster on yarrow. These three aphld species were vectors of beet western yellows virus (BWYV), while hosts of BWYV include the weed species named. It is suggested that BWYV has. a broad ecological base of hosts and vectors In Canterbury.