Comparative fitness of Proprioseiopsis asetus (Acari: Phytoseiidae) as a biocontrol agent against Megalurothrips usitatus and Thrips flavus.

Abstract

Proprioseiopsis asetus (Chant) (Acari: Phytoseiidae) is a newly developed and commercialized predatory mite that can prey on various phytophagous mites and small insects. To evaluate its potential as a biocontrol agent against pest thrips (Thysanoptera: Thripidae), we constructed age-stage, two-sex life tables and investigated the biological characteristics of P. asetus fed on two economically important thrip species, Megalurothrips usitatus and Thrips flavus (Thysanoptera: Thripidae), both of which cause significant crop damage. Our results show that P. asetus successfully develops and reproduces when fed on both thrips species, indicating its biocontrol potential against these pests. However, P. asetus reared on T. flavus exhibits shorter preadult duration, mean generation time (T), and population doubling time (DT), along with obviously reduced longevity, compared to P. asetus reared on M. usitatus. Despite the shorter lifespan, P. asetus fed on T. flavus shows significantly higher fecundity (F = 36.35 eggs/female), intrinsic rate of increase (r = 0.1816 d^-1) and finite rate of increase (λ = 1.1991 d^-1) than on M. usitatus (F = 30.75 eggs/female, r = 0.1375 d^-1 and λ = 1.1474 d^-1). Notably, no significant differences were observed in net reproductive rate (R₀), adult preoviposition period (APOP), total oviposition period (TPOP), or oviposition duration between the two prey species. These findings indicate that P. asetus is a promising biological control agent for both thrip species, with T. flavus being a more suitable prey to support its rapid development, high fecundity and faster population growth, despite the trade-off in adult longevity. Based on these results, we propose tailored biocontrol strategies: frequent releases of P. asetus for T. flavus management to compensate for its shorter lifespan, and early release for M. usitatus to establish a population before the pest reaches damaging levels, aiming for more efficient and sustainable pest management in crop production systems.