Effects of plant age, leaf age and virus yellows infection on the population dynamics of Myzus persicae (Homoptera: Aphididae) on sugarbeet in field plots

Field experiments in which clip-caged apterae of Myzus persicae (Sulzer) (Homoptera: Aphididae) were monitored on sugarbeet revealed that leaf age, plant age and infection of the host with beet yellows closterovirus (BYV) had very large effects on aphid performance (development, reproduction and survival). On healthy plants performance was much better on young, expanding heart leaves than on older leaves. performance on senescent leaves was poor. When apterae were kept on young heart leaves all their lives (by moving clip-cages to younger leaves every 4 days) there was a strong negative relationship between aphid performance and plant age (measured as plant leaf number at birth). On plants inoculated with BYV apterae showed large improvements in performance. These occurred so rapidly that nymphs born at the time of virus inoculation could benefit as much as those born later. The sizes and between-leaf distributions of M. persicae populations which developed from standard numbers of colonists on whole plants in cages were consistent with the results of the clip-cage experiments. Alatae were less sensitive than apterae to differences in plant and leaf age. Implications of the results for BYV epidemiology and control are discussed.