Effects of Sublethal Concentrations of Pyridaben on Development, Reproduction, and Vg Gene Expression in Neoseiulus womersleyi

TL;DR

This study shows that low levels of the pesticide pyridaben harm a beneficial predatory mite by reducing its lifespan, reproduction, and population growth.

Contribution

The study identifies and functionally characterizes two vitellogenin genes in Neoseiulus womersleyi for the first time.

Findings

Sublethal pyridaben exposure reduced the lifespan and egg-laying of F0 mites.

Pyridaben suppressed population growth and delayed development in the next generation (F1).

RNAi silencing of NwVg1 or NwVg2 caused similar reproductive impairments as pyridaben exposure.

Abstract

Predatory mites are important natural enemies used in agriculture to control pest mites. However, they can be harmed by chemical pesticides, even at low concentrations that are not immediately lethal. This study investigated how low (sublethal) concentrations of a common acaricide, pyridaben, affect a beneficial predatory mite, Neoseiulus womersleyi. We found that exposure to these sublethal doses reduced the lifespan and egg-laying ability of the directly exposed generation (F0). It also negatively impacted the next generation (F1), slowing down their development, reducing survival of young mites, and ultimately suppressing the population’s growth rate. For the first time, we identified and studied two key genes in this mite, NwVg1 and NwVg2, which are crucial for egg production. Pyridaben exposure lowered the activity of these genes. When we experimentally turned off these genes, the mites showed similar problems in reproduction and survival as those exposed to the pesticide. Our results show that pyridaben can seriously harm this beneficial predator by damaging its health and disrupting its reproductive genes.

The predatory mite Neoseiulus womersleyi is a key natural enemy in Integrated Pest Management (IPM), but its efficacy is threatened by non-target effects of acaricides like pyridaben. This study evaluated the transgenerational sublethal effects of pyridaben (LC30 and LC50) on N. womersleyi and explored the role of vitellogenin (Vg) genes. Using two-sex life table analysis, we found that exposure reduced longevity, fecundity, and oviposition period in F0 females, while prolonging immature development and suppressing population growth parameters (r, λ) in F1. Two Vg genes (NwVg1 and NwVg2) were cloned and characterized; their expression was significantly downregulated by pyridaben. RNAi-mediated silencing of NwVg1 or NwVg2 recapitulated the pyridaben-induced reproductive impairments, confirming their functional role. Our results demonstrate that pyridaben imposes multigenerational costs and that its reproductive toxicity is mediated, at least in part, through the suppression of Vg synthesis.

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