Two-sex life tables of bifenthrin-selected and unselected strains of Chrysoperla carnea: stability of resistance.

Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is an important agricultural biocontrol agent that preys on various soft-bodied insect pests. This study was carried out to evaluate the fitness parameters of bifenthrin-selected (Bifen-Sel) and unselected (Unsel) strains of C. carnea and their reciprocal crosses (C₁ and C₂) by using an age-stage and two-sex life table approach. After continuous selection with bifenthrin (44 generations), the Bifen-Sel strain of C. carnea developed a 9.55-fold resistance level when compared to that of the Unsel. Biological parameters, such as the pupal period, pre-adult duration, male and female longevity, adult pre-oviposition period, and oviposition period of the Bifen-Sel strain, all were significantly different from that of the Unsel strain and their crosses C₁ and C₂. The larval period, total pre-oviposition period, female ratio, reproductive female ratio, and fecundity of the Bifen-Sel strain were significantly different from those of the Unsel strain. Demographic parameters, including intrinsic rate (r_m), finite rate (λ), net reproductive rate (R₀), mean generation rate (T), and gross reproductive rate of the Bifen-Sel strain, were similar to those of the Unsel strain but significantly higher than those of the C₁ and C₂ crosses of C. carnea. Bifenthrin resistance was stable in the Bifen-Sel strain of C. carnea. These findings provide valuable insights into bifenthrin resistance dynamics in C. carnea as it resulted in no fitness cost and support its selective use under controlled conditions, while highlighting the need for future research on predation potential of this resistant strain under field conditions with bifenthrin applications.