Ex ante analyses to predict the efficacy of natural enemies in biological control

Global annual losses from invasive species are more than one trillion US$. Furthermore, the success rate of biological control (BC) efforts against invasive species is historically low, largely because the pre-release efficacy of putative natural enemies is unknown. Reviews of prior BC efforts have not led to the development of a roadmap to increase the success rate. As an alternative, we deconstructed the highly successful biological control of the invasive cassava mealybug (CM) and cassava green mite (CGM) in Africa using a mechanistic meta population tri-trophic physiologically based demographic model (PBDM) that predicts the efficacy of the natural enemies across vast ecological zones. The model enabled parsing the contribution of each natural enemy and native fungal pathogens to the control of CM and CGM and the recovery of cassava yield. The analysis reveals control would have failed if only some of the natural enemy species had been introduced. PBDMs analyses of other BC efforts show why success or failure occurred and strongly suggests similar analyses could predict pre-release efficacy of natural enemies in future BC programs globally against invasive plant and arthropod species. Such analyses would be an important component in increasing global food security.