Effects of Prey-Mediated Sublethal Exposure to Imidacloprid and Nitenpyram on the Fitness and Predation Capacity in Chrysopa pallens

TL;DR

This study shows how insecticides used to control cotton aphids can harm beneficial green lacewings, even at low doses, by reducing their ability to reproduce and hunt prey.

Contribution

The study reveals novel sublethal effects of imidacloprid and nitenpyram on green lacewings via prey exposure, impacting their predatory and reproductive performance.

Findings

Sublethal insecticide exposure via aphids reduced green lacewing adult body size, fecundity, and prey-capture efficiency.

Imidacloprid suppressed predatory behavior more than nitenpyram, while nitenpyram more strongly delayed development and population growth.

Both insecticides increased handling time and reduced searching efficiency in lacewings, following a Holling type II functional response.

Abstract

The control of cotton aphids, a major pest of cotton, often relies on insecticide applications. This practice, however, can adversely affect non-target beneficial insects that provide essential biological control services. Among these, the green lacewing (Chrysoperla pallens) is a key aphid predator whose role in maintaining field health may be compromised by such insecticide-mediated effects. This study investigated the effects of sublethal doses of imidacloprid and nitenpyram on green lacewings, mediated indirectly through the consumption of exposed aphids. Our results demonstrated that low-dose insecticide exposure mediated by aphids not only delayed larval development and reduced adult body size and fecundity, but also compromised the lacewings’ prey-capture efficiency. The two insecticides affected lacewings in different ways. Imidacloprid significantly compromised foraging efficiency, while nitenpyram more strongly suppressed population growth. This indicates that even non-lethal exposure can reduce the effectiveness of natural pest control. Incorporating these indirect pathways into risk assessments is a critical consideration for developing integrated pest management strategies that protect beneficial predators and promote more sustainable cotton systems.

Chrysopa pallens Stephens (Neuroptera: Chrysopidae) is a key predatory species in cotton agroecosystems. This study investigated the prey-mediated sublethal effects of imidacloprid and nitenpyram at low concentrations (LC20), on C. pallens when exposed via consumption of contaminated prey, assessing impacts on its development and predatory function. C. pallens is a key predatory species in cotton agroecosystems. This study investigated the prey-mediated sublethal effects of imidacloprid and nitenpyram (LC20) on the developmental performance and predatory capacity of C. pallens. Leaf-dipping bioassays were used to assess the toxicity of imidacloprid and nitenpyram to Aphis gossypii Glover (Hemiptera: Aphididae). Age-stage, two-sex life table analysis was conducted to evaluate their subsequent effects on the life history traits and predation performance of C. pallens. Imidacloprid was more toxic to A. gossypii than nitenpyram. Sublethal exposure marginally prolonged larval development, but the effect was not statistically significant. Both insecticides significantly extended the pupal stage, with nitenpyram inducing a greater delay. Imidacloprid markedly increased adult longevity, and both compounds significantly reduced female fecundity. Imidacloprid also suppress predatory behavior more potently, decreasing daily adult consumption and reducing first-instar attack rates by approximately 30%. Although all treatments followed a Holling type II functional response, both insecticides increased handling time and reduced searching efficiency. Overall, imidacloprid primarily inhibited predatory performance, whereas nitenpyram more strongly prolonged development and reduced critical population growth parameters. These findings provide essential evidence for ecological risk assessment and for refining the incorporation of natural enemies into cotton integrated pest management (IPM) strategies.

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