Male-killing bacteria as agents of insect pest control.
Continual effort is needed to reduce the impact of exotic species in the context of increased globalization. Any innovation in this respect would be an asset. We assess the potential of combining two pest control techniques: the well-established sterile insect technique (SIT) and a novel male-killing technique (MKT), which comprises inoculation of a pest population with bacteria that kill the infected male embryos. Population models are developed to assess the efficiency of using the MKT for insect pest control, either alone or together with the SIT. We seek for conditions under which the MKT weakens requirements on the SIT. Regarding the SIT, we consider both non-heritable and inherited sterility. In both cases, the MKT and SIT benefit one another. The MKT may prevent the SIT from failing when not enough sterilized males are released due to high production costs and/or uncertainty on their mating ability following a high irradiation dose. Conversely, with already established SIT, pest eradication can be achieved after introduction of male-killing bacteria with lower vertical transmission efficiency than if the MKT was applied alone. For tephritid fruit flies with non-heritable sterility, maximal impact of the SIT is achieved when the released males are fully sterile. Conversely, for lepidopterans with inherited sterility, maximal impact of the SIT is achieved for intermediate irradiation doses. In both cases, increasing vertical transmission efficiency of male-killing bacteria benefits the SIT; high enough vertical transmission efficiency allows for pest eradication where the SIT is absent or induces only pest suppression when used alone. Synthesis and applications. While both techniques can suppress or eliminate the pest on their own, combined application of the male-killing technique and the sterile insect technique substantially increases pest control efficiency. If male-killing bacteria are already established in the pest, any assessment of the sterile insect technique needs to account for their presence; otherwise, management recommendations could be exaggerated and unnecessarily costly.