Norris Edmund J, Bloomquist Jeffrey R
United States Department of Agriculture, Center for Medical, Agricultural, and Veterinary Entomology, Gainesville, FL 32610, USA.
Emerging Pathogens Institute, Entomology and Nematology Department, University of Florida, Gainesville, FL 32610, USA.
Insects. 2021 Feb 11;12(2):154. doi: 10.3390/insects12020154.
With insecticide-resistant mosquito populations becoming an ever-growing concern, new vector control technologies are needed. With the lack of new chemical classes of insecticides to control mosquito populations, the development of novel synergists may improve the performance of available insecticides. We screened a set of 20 plant essential oils alone and in combination with natural pyrethrins against (Orlando) female adult mosquitoes to assess their ability to synergize this natural insecticide. A co-toxicity factor analysis was used to identify whether plant oils modulated the toxicity of natural pyrethrins antagonistically, additively, or synergistically. Both knockdown at 1 h and mortality at 24 h were monitored. A majority of oils increased the toxicity of natural pyrethrins, either via an additive or synergistic profile. Many oils produced synergism at 2 µg/insect, whereas others were synergistic only at the higher dose of 10 µg/insect. Amyris, cardamom, cedarwood, and nutmeg East Indies (E.I.) oils were the most active oils for increasing the mortality of natural pyrethrins at 24 h with co-toxicity factors greater than 50 at either or both doses. A number of oils also synergized the 1 h knockdown of natural pyrethrins. Of these, fir needle oil and cypress oils were the most successful at improving the speed-of-action of natural pyrethrins at both doses, with co-toxicity factors of 130 and 62, respectively. To further assess the co-toxicity factor method, we applied selected plant essential oils with variable doses of natural pyrethrins to calculate synergism ratios. Only the oils that produced synergistic co-toxicity factors produced statistically significant synergism ratios. This analysis demonstrated that the degree of co-toxicity factor correlated well with the degree of synergism ratio observed (Pearson correlation coefficient r = 0.94 at 2 µg/insect; r = 0.64 at 10 µg/insect) and that the co-toxicity factor is a useful tool in screening for synergistic activity.
随着抗杀虫剂蚊虫种群问题日益受到关注，需要新的病媒控制技术。由于缺乏用于控制蚊虫种群的新型化学类别杀虫剂，新型增效剂的开发可能会提高现有杀虫剂的性能。我们单独筛选了一组20种植物精油，并将其与天然除虫菊酯组合，用于测试对（奥兰多）雌性成年蚊子的效果，以评估它们使这种天然杀虫剂增效的能力。采用共毒系数分析来确定植物油是拮抗、相加还是协同调节天然除虫菊酯的毒性。监测了1小时时的击倒率和24小时时的死亡率。大多数精油通过相加或协同作用增强了天然除虫菊酯的毒性。许多精油在2微克/只昆虫时产生协同作用，而其他精油仅在10微克/只昆虫的较高剂量下才具有协同作用。香脂木、小豆蔻、雪松木和肉豆蔻东印度群岛（E.I.）精油是最具活性的精油，在24小时时可提高天然除虫菊酯的死亡率，在任一剂量或两个剂量下共毒系数均大于50。一些精油还对天然除虫菊酯的1小时击倒率有协同作用。其中，枞叶油和柏木油在两个剂量下对提高天然除虫菊酯的作用速度最为成功，共毒系数分别为130和62。为了进一步评估共毒系数法，我们应用选定的植物精油与不同剂量的天然除虫菊酯来计算协同比率。只有产生协同共毒系数的精油才产生具有统计学意义的协同比率。该分析表明，共毒系数的程度与观察到的协同比率程度密切相关（在2微克/只昆虫时皮尔逊相关系数r = 0.94；在10微克/只昆虫时r = 0.64），并且共毒系数是筛选协同活性的有用工具。
