# Evaluating the Direct and Indirect Toxicity of Nine Insecticides on an Important Predatory Natural Enemy in Rice Fields

## TL;DR

This study evaluates how nine insecticides affect six natural predators in rice fields, finding some are safe while others are highly toxic.

## Contribution

The study provides a comparative analysis of insecticide toxicity to multiple natural enemies, identifying safer options for integrated pest management.

## Key findings

- Tetraniliprole, triflumezopyrim, and chlorantraniliprole showed minimal toxicity to six predatory species.
- Spinetoram, avermectin, and emamectin benzoate caused high direct and indirect toxicity to all six predators.
- Pymetrozine, nitenpyram, and imidacloprid significantly reduced predatory activity and caused high mortality.

## Abstract

Natural enemies play a crucial role in suppressing insect pests in rice ecosystems, but their safety is often neglected during insecticide selection. This study compared the effects of nine commonly used insecticides on six important predatory natural enemies of rice pests. The results showed clear differences in insecticide safety. Tetraniliprole, triflumezopyrim, and chlorantraniliprole had minimal direct or indirect toxicity to predators, indicating good compatibility with biological control. In contrast, spinetoram, pymetrozine, nitenpyram, imidacloprid, emamectin benzoate, and avermectin caused high direct or indirect toxicity to all six predators, including green mirid bugs, rove beetles, and spiders. These findings highlight the importance of selecting insecticides that effectively control rice pests while conserving beneficial natural enemies.

Natural enemies play an important role in the integrated pest management (IPM) of rice crops. Chemical control is commonly used for pest management in rice; however, the compatibility between biological and chemical control within this system has not been thoroughly investigated. This study aimed to evaluate both the direct and indirect toxicity of nine insecticides—tetraniliprole, triflumezopyrim, chlorantraniliprole, pymetrozine, spinetoram, nitenpyram, imidacloprid, emamectin benzoate, and avermectin—against six important predators of rice pests: Cyrtorhinus lividipennis, Paederus fuscipes, Ummeliata insecticeps, Tetragnatha maxillosa, Mendoza cancestrinnii, and Pardosa pseudoannulata under laboratory conditions. The results indicated that tetraniliprole, triflumezopyrim, and chlorantraniliprole exhibited negligible direct toxicity (mortality < 30%) to all six predators and did not significantly affect their predatory activity. In contrast, spinetoram, avermectin, emamectin benzoate, nitenpyram, and imidacloprid showed high direct toxicity (mortality > 99%), significantly reduced predatory activity, and were classified as high to extremely high risk for C. lividipennis. Nitenpyram showed strong direct toxicity (mortality > 99%) to P. fuscipes and was categorized as high risk. Avermectin and emamectin benzoate exhibited high direct and indirect toxicity to all four spider species, significantly reducing predatory activity, and were graded from medium to extremely high risk. Spinetoram reduced predatory activity across all four spider species and exhibited direct toxic effects, posing a high risk to U. insecticeps. In conclusion, pymetrozine, spinetoram, nitenpyram, imidacloprid, emamectin benzoate, and avermectin exerted lethal or sublethal effects on all six predators. Conversely, tetraniliprole, triflumezopyrim, and chlorantraniliprole were regarded as safer insecticides for all six predators.