The role of flying aphid vectors in the transmission of cucumber mosaic virus and potato virus Y to peppers in Israel

More than 44 species of aphids were trapped by suction during the spring seasons of 1981, 1982 and 1983 over a pepper field at Bet Dagan, Israel. Nineteen species transmitted cucumber mosaic virus (CMV), while seven transmitted potato virus Y (PVY) at least once. Over 80% of the CMV and of the PVY infection among test plants (Capsicum annuum cv. Weindale) exposed to trapped aphids was caused by Aphis citricola and two or three other Aphis species, Myzus persicae and Macrosiphum euphorbiae. Landing rate was determined by comparing the proportion of each species found on green tiles or pepper plants with that found in suction traps. A. citricola was the most common but was found in a much lower proportion on plants than either in flight or on green tiles. Aphis spp. and M. persicae were more than 2–5 times more frequent (relative to other species) on green tiles than in flight. M. persicae and M. euphorbiae, which colonise peppers, were found on peppers at a proportion several times higher than either on green tiles or in the air. The relative importance of the different vector species was calculated by multiplying abundance by the proportion of transmitters and the landing rate. A. citricola and Aphis spp. were responsible for more than 50% of the total transmission of either CMV in 1981 and 1982 and of PVY in 1981. Peaks of CMV infection of bait plants coincided with peaks of transmitters of A. citricola and Aphis spp. caught in suction traps. The significance of these findings in primary infection of peppers with CMV and PVY is discussed.