Effect of Rickettsiella viridis endosymbionts introduced into Myzus persicae aphids on parasitism by Diaeretiella rapae: A combined strategy for aphid control?

Abstract

Aphids are major crop pests in southeastern regions of Australia. Some aphid species harbor heritable facultative endosymbionts that may induce beneficial or detrimental impacts on aphids under certain ecological conditions. Aphid-parasitoid interactions can be greatly affected by facultative endosymbionts but there is still limited research on many species of economic significance. Here we assessed the effects of a facultative endosymbiont, Ricketsiella viridis, on parasitism of the major aphid pest, Myzus persicae, by Diaeretiella rapae. We found that R. viridis does not provide M. persicae with significant protection against D. rapae, with parasitoids showing a preference for probing aphids infected with R. viridis. The fecundity of M. persicae is reduced due to infection with R. viridis regardless of the presence of parasitoids. Moreover, we show that parasitoids may facilitate horizontal and subsequent vertical transmission of facultative endosymbionts in aphids which could increase the spread of deleterious effects associated with R. viridis. Based on these findings, simultaneous release of D. rapae and M. persicae infected with R. viridis in the early cropping season (lower population densities and cooler conditions) may contribute to an effective strategy for efficient management of this pest.