Acetamiprid-Induced Toxicity Thresholds and Population Sensitivity in Trichogramma dendrolimi: Implications for Pesticide Risk Assessment

TL;DR

This study shows that the pesticide acetamiprid can harm beneficial insects like Trichogramma dendrolimi at low concentrations, affecting their reproduction and survival.

Contribution

The study introduces a new method to assess pesticide risks by incorporating sublethal effects on beneficial insect populations.

Findings

Acetamiprid at low concentrations significantly reduces parasitism and emergence rates in Trichogramma dendrolimi.

Field concentrations of acetamiprid could affect up to 97.9% of similar beneficial insect populations.

Sublethal effects of acetamiprid include shortened offspring development and reduced reproductive success.

Abstract

Insects like the Trichogramma dendrolimi are essential for controlling harmful pests in agriculture. However, pesticides used to kill these pests can also harm beneficial insects like T. dendrolimi. This study examined the effects of a common pesticide, acetamiprid, on T. dendrolimi. It found that even small amounts of acetamiprid can reduce the ability of T. dendrolimi to lay eggs and survive, without necessarily killing them. By using a statistical model, the study also showed that acetamiprid could affect a large portion of similar beneficial insects at commonly used field concentrations. These findings highlight the importance of considering not just whether a pesticide kills insects, but also its subtle effects on beneficial insects that help control pests naturally. This information can help improve pest management strategies to better protect both crops and beneficial insects.

Trichogramma dendrolimi, a key egg parasitoid for lepidopteran pest control, faces potential risks from neonicotinoid insecticides like acetamiprid used in integrated pest management (IPM). This study evaluated acetamiprid’s acute and sublethal toxicity to T. dendrolimi and assessed population-level risks via species sensitivity distribution (SSD). Acute toxicity assays using glass-vial residues revealed a 24 h LC50 of 0.12 mg a.i. L−1 for adults, three orders of magnitude below the maximum field rate (100 mg a.i. L−1). Sublethal exposure (1/2–1/100 LC50) significantly reduced parasitism and emergence rates (NOEC = 2.3 μg a.i. L−1) but did not affect offspring survival. Acetamiprid also shortened offspring development at 11.5–57.5 μg a.i. L−1. SSD analysis identified T. dendrolimi as the most sensitive parasitoid to acetamiprid (HC5/HC50) = 0.11/5.88 mg a.i. L−1), with field rates (30–100 mg a.i. L−1) indicating a potentially affected fraction (PAF) of 76.8–97.9%. These findings underscore the need to integrate sublethal effects into pesticide regulations to conserve parasitoid-mediated ecosystem services.

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