Some factors affecting the transmission of sugar‐beet mosaic and pea mosaic viruses by Aphis fubue and Myzus persicae

SUMMARY Alate Aphis fabae were often less efficient vectors than Myzus persicae of pea mosaic virus and sugar‐beet mosaic virus. Flight‐mature A. fabae rarely transmitted these viruses unless they had either flown (tethered) or fasted for several hours before feeding on infected plants; by contrast, flight‐mature M. persicae transmitted either virus before flying or fasting, though more frequently afterwards. There was little difference in the infectivity of the two species after they had flown and then fed for a short time on infected plants. Aphids flown for 1–5 hr. and then allowed a short feed on infected plants transmitted only slightly more often than aphids flown for 15 min., but they remained on the host plants longer. After flying for 15–60 min., many A. fabae settled permanently on broad bean plants, and a few on sugar‐beet plants, but most M. persicae flew off after feeding on these plants for a few hours. Many flight‐mature alatae of both species probed briefly before flying from a plant for the first time; more M. persicae than A. fabae transmitted after such pre‐flight probing on infected plants. The infectivity of flying or fasting alatae, and fasting apterae, decreased at similar rates. The rate of decrease was accelerated as the temperature rose, and few aphids transmitted after 30 min. at temperatures above 30 °C. PMV and SBMV, but not henbane mosaic virus, were transmitted more often by alatae than by apterae. The species of plant (broad bean or sugar beet) on which aphids developed did not affect their ability to transmit PMV or SBMV.