Systemic Assessment of Chronic Toxicity of Thiamethoxam on Honeybees (Apis mellifera)
by
, ,
Meng-Jia Li
1,2,†, 
Qi-Bao He
2,†,
Yi-Fan Wu
2,
Quan Gao
2,
A-Long Wang
2,
Jin-Jing Xiao
2,
Min Liao
2,
Yong Huang
2,
Yao-Hui Wang
2,* and
Hai-Qun Cao
2,* 1
College of Resources and Environment, Anhui Agricultural University, Hefei 230036, China
2
Anhui Province Key Laboratory of Crop Integrated Pest Management, School of Plant Protection, Anhui Agricultural University, Hefei 230036, China
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Insects 2025, 16(9), 936; https://doi.org/10.3390/insects16090936
Submission received: 5 August 2025
/
Revised: 31 August 2025
/
Accepted: 3 September 2025
/
Published: 5 September 2025
(This article belongs to the Section Social Insects and Apiculture)
Simple Summary
The unreasonable use of pesticides has contributed to a significant decrease in honeybees and unsustainable colony loss. This phenomenon has caused wide public concern in many places around the world. While the majority of current risk assessments have addressed the health of workers, they rarely refer to the queen and drone bees. Based on our previous nationwide monitoring of pesticide residues in royal jelly and other samples in the main honey-producing areas in China, we selected thiamethoxam with a high detection rate and concentration as the test pesticide to test whether it affects reproductive bee development and adversely impacts health and viability. We evaluated the effects of thiamethoxam on the entire larval development cycle of reproductive bees and conducted a comparative analysis, demonstrating that thiamethoxam significantly alters ecdysone and juvenile hormone titers in both queen and drone larvae, impairing metamorphosis and reproductive development.
Abstract
Honeybees (Apis mellifera ligustica Spin.) are the most significant pollinating insects, playing a vital role in maintaining biodiversity. In healthy colonies, the reproductive success of the queen and the genetic contribution of drones are essential for long-term survival, directly affecting brood production, genetic diversity, and environmental adaptability. While the physiological and behavioral impacts of chemical pesticides on worker bees are relatively well documented, the risks to reproductive bees (queens and drones) remain poorly understood. In this study, we comprehensively assessed the effects of the widely used neonicotinoid thiamethoxam on the key developmental and physiological parameters in reproductive bees, including survival, pupation rate, eclosion rate, hormone titers, and detoxification enzyme activities. Our finding reveals that thiamethoxam exerts sublethal effects on larvae, significantly impairing the fitness of reproductive bees. Specifically, exposure altered juvenile hormone III, ecdysone titer, and acetylcholinesterase activity in reproductive larvae, with these effects showing a negative correlation with pesticide concentration. Notably, CYP450 activity exhibits a biphasic dose–response, with an initial elevation followed by a decline after reaching peak levels. These results demonstrate that thiamethoxam adversely affects the growth and development of reproductive bees, potentially compromising colony stability. By elucidating these sublethal effects, our study provides critical insights for mitigating pesticide-related threats to honeybee health. Our findings may help to scientifically and rationally avoid the potential risks of chemical pesticides to honeybees.
