DO MYZUS (NECTAROSIPHON) SPECIES OTHER THAN M-PERSICAE POSE A THREAT TO THE IDAHO POTATO CROP

Green peach aphids (Myzus persicae (Sulzer)) pose a threat to the Idah o potato (Solanum tuberosum L.) crop primarily because they transmit p otato leafroll virus (PLRV). Only colonizing vectors are epidemiologic ally significant because PLRV is persistently transmitted. Additionall y, Idaho winters are severe enough that most permanently anholocyclic aphid species do not establish. It is now accepted that the taxon that has been known as Myzus (Nectarosiphon) persicae (Sulzer) is in fact at least three species (M. persicae, Myzus nicotianae Blackman and Myz us antirrhinii (Macchiati)). It was not known whether the newly design ated species had the potential to damage the Idaho potato crop, The ob jectives of our research were to determine whether Myzus (Nectarasipho n) spp. other than M. persicae occurred naturally in Idaho, whether th ey could colonize potato and transmit PLRV, and whether they were pote ntially holocyclic. No Myzus (Nectarosiphon) spp. other than M. persic ae were found in Idaho in trap nurseries; however Myzus ascalonicus Do ncaster recently has been found on stored bulbs and in suction trap co llections in north Idaho. Laboratory bioassays for PLRV vector potenti al using Physalis floridana Rydb. indicator plants show that M., nicot ianae can transmit PLRV as efficiently as M. persicae. Similarly, M. n icotianae colonized potato as well as M. persicae in a replicated labo ratory experiment comparing two clones of M. nicotianae and one clone of M. persicae. Our observations indicate that North American M. nicot ianae may be capable of a limited facultative holocycle. Thus, in labo ratory experiments, M. nicotianae is as damaging as M. persicae with r espect to PLRV vector potential; however, M. nicotianae may not occur naturally in areas like Idaho that have no tobacco production. A summa ry of all Myzus (Nectarosiphon) SPP with respect to PLRV epidemiology is provided.