印楝油对兔疥螨幼虫的体外杀螨活性

Acaricidal activity of neem oil against Sarcoptes scabiei var.cuniculi larvae in vitro

将兔疥螨幼虫置于聚苯乙烯小平皿中,分别加入不同浓度的印楝油液体石蜡溶液,以天然除虫菊酯和阿维菌素为阳性对照,蒸馏水和液体石蜡为阴性对照,观察记录不同时间段的螨虫死亡数,以死亡率、半数致死时间(LT50)和半数致死浓度(LC50)为指标评价了印楝油对兔疥螨幼虫的离体杀螨活性。结果显示,未稀释的印楝油能在25 min内杀死所有幼螨,其杀螨活性显著强于500 g/L的天然除虫菊酯(825 min,P<0.01),而与25 g/L的阿维菌素无显著差异(19 min,P>0.05);500、250和125 mL/L印楝油对兔疥螨幼虫的LT50分别为1、2、5 h;24 h的LC50和LC95分别为2.908和12.018 mL/L。结果证实,印楝油对兔疥螨幼虫具有较好的离体杀螨活性。

Sarcoptes scabiei var. cuniculi larvae were placed into small polystyrene petri dishes, and different concentration of paraffin solution of neem oil was directly added into them. 500 g/L pyrethrins and 25 g/L avermectin were used as treated control,while distilled water and paraffin oil represented untreated control. The number of dead mites was examined at different time points,and the mortality,median lethal time（LT50 ） and median lethal concentration（LC50 ） were used to evaluate the acaricidal activity of neem oil against S. scabiei var. cuniculi larvae in vitro. The undiluted neem oil killed all larvae in 25 rain. The acaricidal activity of the undiluted neem oil was significantly higher than that of 500 g/L pyrethrins（825 min, P〈0.01）, but not significantly different from that of 25 g/L avermectin（19 min, P〉0.05）. The LT50 values of 500,250 and 125 mL/L neem oil against S. scabiei larvae were 1,2 and 5 h,respectively. The LC50 and LC95 values were 2. 908 and 12. 018 mL/L 24 hours post-treatment,respectively. These results demonstra- ted that the neem oil had good effect against S. scabiei var. cuniculi larvae in vitro.