Biosciences, College of Life & Environmental Sciences, University of Exeter, Hatherly Laboratories, Exeter, UK.
Pest Manag Sci. 2020 Aug;76(8):2846-2853. doi: 10.1002/ps.5838. Epub 2020 Apr 22.
Farmland bees encounter insecticides in their diet when visiting the flowers of pesticide-treated crops with residues in nectar and pollen. A sustained exposure to even trace residues could be severely harmful if the ingested substance has a long biological half-life and its toxicity therefore intensifies over time, which is termed time-reinforced toxicity (TRT). Bumble bees are important farmland pollinators, but their susceptibility to TRT from insecticides has not been established previously. This study therefore investigated the potential for three farmland insecticides (imidacloprid, thiamethoxam and fipronil) to generate TRT in bumble bees (Bombus terrestris L.) by dietary exposure in the laboratory using lethality as an endpoint under both fixed-dose and pulsed-dose regimes.
The insecticides varied in toxic effect. Fipronil exposures produced a dose-dependent reduction in longevity (days of exposure survived) and strong TRT with no evidence of clearance-based recovery. Thiamethoxam exposures also produced a dose-dependent reduction in longevity, but with moderate TRT and evidence of some clearance-based recovery. Imidacloprid exposures produced a hormesis with reduced longevity only at the highest doses and an absence of TRT.
Our study further confirms the potential for certain dietary insecticides at trace levels to harm farmland bees during sustained exposures because of their capacity to cause time-reinforced toxicity. Our findings suggest that regulatory oversight of pesticides will better safeguard bee health by testing the active ingredients of farmland agrochemicals for their capacity to produce TRT in these ecologically important nontarget organisms. Our study demonstrates the potential for certain dietary insecticides at trace levels to harm farmland bumble bees during sustained exposures because of their capacity to cause time-reinforced toxicity. © 2020 Society of Chemical Industry.
农田蜜蜂在访问施药作物花朵时会在饮食中接触到杀虫剂，这些杀虫剂在花蜜和花粉中残留。如果摄入的物质半衰期长，其毒性随着时间的推移而加剧，即使是微量残留也会对其造成持续暴露，这种现象被称为时间强化毒性（TRT）。大黄蜂是重要的农田传粉媒介，但它们对杀虫剂 TRT 的敏感性以前尚未确定。因此，本研究通过实验室饮食暴露，使用固定剂量和脉冲剂量方案，以死亡率为终点，研究了三种农田杀虫剂（吡虫啉、噻虫嗪和氟虫腈）对大黄蜂（Bombus terrestris L.）产生 TRT 的可能性。
杀虫剂的毒性作用不同。氟虫腈暴露会导致寿命（暴露天数）依赖性降低和强烈的 TRT，没有清除恢复的证据。噻虫嗪暴露也会导致寿命依赖性降低，但 TRT 适中，有一定的清除恢复证据。吡虫啉暴露会产生激素反应，只有在最高剂量下才会降低寿命，而且不存在 TRT。
我们的研究进一步证实，在持续暴露的情况下，由于某些饮食性杀虫剂具有产生时间强化毒性的能力，即使在痕量水平下也可能对农田蜜蜂造成伤害。我们的研究结果表明，通过测试农田农用化学品的有效成分是否具有在这些生态重要的非靶标生物中产生 TRT 的能力，对农药进行监管监督将更好地保护蜜蜂健康。我们的研究表明，在持续暴露的情况下，由于某些饮食性杀虫剂具有产生时间强化毒性的能力，即使在痕量水平下也可能对农田大黄蜂造成伤害。© 2020 英国化学学会。
