Selective Breeding and Trait Improvement of Insect Natural Enemies for Ecologically Robust Biological Control

Insect natural enemies are central agents in biological-control programs. Their pest-suppression performance depends not only on release strategy, but also on traits shaped by long-term laboratory rearing and selection. Conventional mass-rearing systems usually evaluate insect natural enemies using production-oriented indicators, such as survival, fecundity, emergence rate, sex ratio and production cost. However, continuous mass rearing can drive laboratory adaptation, genetic drift, inbreeding, shifts in host or prey use, and reduced field performance. In this review, we summarize key target traits for insect natural enemy improvement, including production efficiency, host or prey use, parasitism, predation, nonreproductive host killing, stress tolerance, pesticide compatibility, dispersal, retention and field efficacy. We further discuss how recurrent artificial selection, hybridization, population genetics, and genomics approaches can be integrated to improve insect natural enemies while maintaining genetic quality. Finally, we discuss the links among trait screening, selection design, quality control, storage and transport, and field-performance validation in the development and application of selected lines or improved strains. Overall, this review highlights practical directions for developing stable and field-proven natural enemy lines. Beyond agriculture, this perspective may also support ecological design in urban landscapes through natural enemy conservation and reduced pesticide use.