Effect of hexythiazox and spiromesifen resistance on the life cycle of the predatory mite Neoseiulus californicus (Acari: Phytoseiidae).

Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is one of the most important and effective predators of Tetranychus spp. (Acari: Tetranychidae). This study analyzed the effects of hexythiazox and spiromesifen resistance on biological characteristics of N. californicus. Pre-oviposition, oviposition, post-oviposition times, adult lifespan, total number of eggs laid per female, net reproductive rate (R0), intrinsic rate of increase (rm), doubling time (DT), mean generation time (T) and finite rate of increase (λ) were compared among three populations: 63.9-fold hexythiazox resistant (HEX14), 53.6-fold spiromesifen resistant (SPR13) and a susceptible base population. Pre-oviposition and oviposition times, mean number of eggs/female, adult lifespan, R0 and rm values were all significantly higher for the two resistant populations than for the susceptible population. Life tables of HEX14, SPR13 and the susceptible population showed that R0 was 35.0, 26.5 and 19.4 (females/female generation), rm was 0.35, 0.32 and 0.30 (females/female/day), DT was 1.92, 2.07 and 2.27 days, T was 9.8, 9.8 and 9.7 days, and λ was 1.43, 1.39 and 1.35 (individuals/female/day), respectively.