Host-adapted parasitoids in biological control: does source matter?

It has been hypothesized that the success of a biological control introduction is, in part, dependent on the ability of the control agent to become established in its new environment or to its new population of hosts through local adaptation. Despite this, few studies have investigated the influence of the recent coevolutionary history of pest species and natural enemies on the efficacy of biological control agents, especially for agents that are mass-reared for release in agriculture. We investigate the evolutionary potential of a biological control agent Aphidius ervi to adapt to a key pest species, the foxglove aphid Aulacorthum solani, through components essential to the evolution of parasitoid virulence. We explored (1) the influence of genetic variation from natural source populations on the ability to parasitize natal and non-natal host species; (2) the heritability of key traits related to parasitoid fitness; and (3) the efficacy of parasitoid host-selection lines in a greenhouse system. Source populations maintained genetic variation in the ability to utilize natal and non-natal host species; however, only some of the traits sampled suggested local adaptation of parasitoid populations. The ability to parasitize a host was found to be genetically determined and strongly heritable, irrespective of host species. The greenhouse study demonstrated the potential of parasitoid selection lines to substantially increase performance of parasitoids for target pest species. This research provides insight into novel techniques that can be used to increase the quality of biological control agents through the development of lines of natural enemies adapted to particular pest species.