From suboptimal prey to optimal performance: selective breeding improves Orius laevigatus performance on a low-cost...

The mass production of the generalist predator Orius laevigatus currently relies on expensive factitious prey, such as Ephestia kuehniella eggs. While astigmatid mites offer a low-cost alternative, their use has been historically limited by a significant decline in predator fecundity and fitness. This study evaluates the success of a 15-generation selection program aimed at developed strains adapted to an astigmatid mite diet (Acarus siro). We compared two selected lines (MITE1-15 and MITE2-15) against a commercial population. Our results show that the MITE2-15 line overcame the reduced fecundity typically associated with alternative prey, reaching oviposition on A. siro comparable to E. kuehniella. Furthermore, this genetic gain in reproductive output was achieved without physiological trade-offs, as the selected lines maintained standard morphological size, improved developmental time, and exhibited high survival rates across multiple astigmatid species, including Suidasia medanensis and Carpoglyphus lactis. A significant population-diet interaction confirms that targeted selection leads to a synergistic adaptation superior to generalist stress-tolerance strategies. These findings represent an advance in the development of improved natural enemies, providing the biocontrol industry with a robust, cost-effective strategy to replace expensive factitious prey without compromising the quality or resilience of the mass-reared predators.