Zhu Yu Cheng, Yao Jianxiu, Adamczyk John, Luttrell Randall
USDA-ARS, Stoneville, Mississippi, United States of America.
USDA-ARS, Poplarville, Mississippi, United States of America.
PLoS One. 2017 May 3;12(5):e0176837. doi: 10.1371/journal.pone.0176837. eCollection 2017.
Imidacloprid is the most widely used insecticide in the world. In this study, we used spraying methods to simulate field exposures of bees to formulated imidacloprid (Advise® 2FL) alone and binary mixtures with seven pesticides from different classes. Synergistic toxicity was detected from mixtures of Advise (58.6 mg a.i./L imidacloprid)+Domark (512.5 mg a.i. /L tetraconazole), Advise+Transform (58.5 mg a.i./L sulfoxaflor), and Advise+Vydate (68 mg a.i./L oxamyl), and mortality was significantly increased by 20%, 15%, and 26% respectively. The mixtures of Advise+Bracket (88.3 mg a.i./L acephate) and Advise+Karate (62.2 mg a.i./L L-cyhalothrin) showed additive interaction, while Advise+Belay (9.4 mg a.i./L clothianidin) and Advise+Roundup (1217.5 mg a.i./L glyphosate) had no additive/synergistic interaction. Spraying bees with the mixture of all eight pesticides increased mortality to 100%, significantly higher than all other treatments. Except Bracket which significantly suppressed esterase and acetylcholinesterase (AChE) activities, other treatments of Advise-only and mixtures with other pesticides did not suppress enzyme activities significantly, including invertase, glutathione S-transferase (GST), and esterase and AChE. Immunity-related phenoloxidase (PO) activities in survivors tended to be more variable among treatments, but mostly still statistically similar to the control. By using specific enzyme inhibitors, we demonstrated that honey bees mainly rely on cytochrome P450 monooxygenases (P450s) for detoxifying Advise, while esterases and GSTs play substantially less roles in the detoxification. This study provided valuable information for guiding pesticide selection in premixing and tank mixing in order to alleviate toxicity risk to honey bees. Our findings indicated mixtures of Advise with detoxification-enzyme-inducing pesticides may help bees to detoxify Advise, while toxicity synergists may pose further risk to bees, such as the Bracket which not only suppressed esterase and AChE activities, but also increased toxicity to bees.
吡虫啉是世界上使用最广泛的杀虫剂。在本研究中，我们采用喷雾法模拟蜜蜂在田间接触单独的配方吡虫啉（Advise® 2FL）以及与七种不同类别的杀虫剂的二元混合物的情况。在Advise（58.6毫克有效成分/升吡虫啉）+Domark（512.5毫克有效成分/升四氟醚唑）、Advise+Transform（58.5毫克有效成分/升氟啶虫胺腈）以及Advise+Vydate（68毫克有效成分/升杀线威）的混合物中检测到协同毒性，死亡率分别显著增加了20%、15%和26%。Advise+Bracket（88.3毫克有效成分/升乙酰甲胺磷）和Advise+Karate（62.2毫克有效成分/升高效氯氟氰菊酯）的混合物表现出相加作用，而Advise+Belay（9.4毫克有效成分/升噻虫胺）和Advise+Roundup（1217.5毫克有效成分/升草甘膦）没有相加/协同作用。用所有八种杀虫剂的混合物对蜜蜂进行喷雾处理会使死亡率增加到100%，显著高于所有其他处理。除了Bracket显著抑制酯酶和乙酰胆碱酯酶（AChE）活性外，其他仅使用Advise以及与其他杀虫剂混合的处理对包括转化酶、谷胱甘肽S-转移酶（GST）以及酯酶和AChE在内的酶活性没有显著抑制作用。存活蜜蜂中与免疫相关的酚氧化酶（PO）活性在各处理间的变化趋势更大，但大多在统计学上仍与对照相似。通过使用特定的酶抑制剂，我们证明蜜蜂主要依靠细胞色素P450单加氧酶（P450s）来解毒Advise，而酯酶和GSTs在解毒过程中起的作用要小得多。本研究为指导预混和桶混中的农药选择以减轻对蜜蜂的毒性风险提供了有价值的信息。我们的研究结果表明，Advise与诱导解毒酶的农药混合可能有助于蜜蜂对Advise进行解毒，而毒性增效剂可能会给蜜蜂带来进一步风险，例如Bracket不仅抑制酯酶和AChE活性，还增加了对蜜蜂的毒性。
