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采用药膜法测定了不同光照条件下天然除虫菊素对桔小实蝇Bactrocera dorsalis(Hendel)成虫的触杀毒力,试图通过毒力的变化来明确除虫菊素用于防治桔小实蝇成虫的光稳定性。测定结果表明,天然除虫菊素在室内(平均光强25.00±0.53KLux)条件下对桔小实蝇成虫仍表现出较好的触杀毒力,其LC50为33.90μg/mL。在黑暗处理和光照处理的对比实验中,经平均光强600.00±1.99KLux的光照处理24h和72h后,除虫菊素对桔小实蝇成虫的触杀活性极显著低于黑暗处理,死亡率分别从98.33和97.67下降到6.65和1.67,表明光照对除虫菊素的杀虫活性影响极大。活性与光照时间的动态关系显示,除虫菊素和对照药剂氯氰菊酯一样,对桔小实蝇成虫的触杀活性随光照时间的增加呈指数型下降,其衰减过程符合一级动力学模型。除虫菊素受光照的活性半衰期为4.90h,明显短于氯氰菊酯的37.46h。
The toxicity of natural pyrethrin to adults of Bactrocera dorsalis (Hendel) under different light conditions was measured by the membrane method. The toxicity of pyrethrin to the light stability of adult adults of Bactrocera dorsalis (Hendel) Sex. The results showed that natural pyrethrins still showed good contact toxicity to adults of the fruit fly, with an LC50 of 33.90μg / mL under laboratory conditions (mean light intensity 25.00 ± 0.53KLux). In the contrast experiment of darkness treatment and light treatment, the contact activity of pyrethrin against adult adults of the fruit fly was significantly lower than that of the dark under the illumination of 600.00 ± 1.99KLux with the average light intensity of 600.00 ± 1.99KLux for 24 and 72 hours, respectively. The mortality rate was 98.33 And 97.67 down to 6.65 and 1.67, respectively, indicating that light has a great effect on the insecticidal activity of pyrethrins. The dynamic relationship between activity and light time showed that the insecticidal activity of pyrethrin and the control agent cypermethrin decreased exponentially with the increase of light time and the decay process accorded with the first-order kinetic model. The active half life of pyrethrin by light was 4.90 h, which was significantly shorter than that of cypermethrin of 37.46 h.