Synergistic toxicity and physiological impact of thiamethoxam alone or in binary mixtures with three commonly used insec
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Original article
Synergistic toxicity and physiological impact of thiamethoxam alone or in binary mixtures with three commonly used insecticides on honeybee Yufei WANG , Wenxin ZHANG , Tengfei SHI , Shengyun XU , Bozhi LU , Hongwei QIN , Linsheng YU Anhui Agricultural University, Hefei 230036, China Received 26 November 2018 – Revised 14 October 2019 – Accepted 13 November 2019
Abstract – As one of the most widely used insecticides, thiamethoxam (Th) plays an important role in agriculture pest control but is hazardous to the health of honeybees (Apis mellifera ligustica ). In agricultural practice, several types of insecticides are often applied simultaneously, but their synergistic effects on honeybees remain elusive. Here, we treated honeybees with various binary mixtures of insecticides in which a sublethal dose of Th was mixed with three other common insecticides: λ-cyhalothrin (λ-cy), β-cypermethrin (β-cy), and abamectin (Ab). The mortality rates of the groups treated with the insecticide mixtures were higher than that obtained with the pesticides alone. Specifically, the Th + λ-cy and Th + Ab combinations exerted a synergistic effect (P < 0.05) on bees and resulted in significantly higher mortality than that obtained with the single treatments. However, the Th + β-cy mixture had no synergistic effect (P > 0.05) on bees, and the mortality rate of this group was almost identical to those of the groups administered these pesticides alone. Furthermore, the Th + λ-cy and Th + Ab mixtures significantly suppressed the activity and expression of glutathione S-transferases (GSTs), which are key detoxification enzymes in insects. This result suggests that the Th + λ-cy and Th + Ab combinations at a given concentration adversely affect the survival of honeybees. Our study provides novel information for the selection of pesticide combinations based on protecting honeybee populations. honeybee / insecticide / thiamethoxam / binary mixture / synergistic effect
1. INTRODUCTION Honeybees are important pollinators of crops and wild plants. Due to their specificity for pollination, relocation, and domestication, honeybees are the most ideal pollinators for agricultural production. Bees simultaneously provide various high valueadded products, such as honey, royal jelly, and beeswax. However, bees have recently been affected by a wide range of biological and abiotic factors (Moritz et al. 2010), such as insecticides, pathogens,
Corresponding author: L. Yu, [email protected] Handling Editor: Monique Gauthier
and parasites (Nazzi and Le Conte 2016), and the separate and combined effects of these factors have led to a significant reduction in the number of bees worldwide (Goulson et al. 2015). This issue should be highlighted and has thus attracted international attention. The abuse of insecticides is probably one reason for the observed reduction in bees. The neonicotinoid insecticides function as nicotinic acetylcholine receptor (nAChR) agonists that selectively bind to nAChRs (Millar & Denholm 2007). Due to their high
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