Vector Control Research Centre (ICMR), Medical Complex, Puducherry, India.
Indian J Med Res. 2009 Nov;130(5):556-60.
BACKGROUND & OBJECTIVE: Pirimiphos-methyl, an organophosphorus insecticide is known to overcome resistance mechanisms of mosquitoes to other organophosphates. Information on the duration of efficacy of pirimiphos-methyl (50% emulsifiable concentrate) for the control of immatures of Culex quinquefasciatus, the vector of bancroftian filariasis, is scanty and hence site specific field trials are necessary to determine the field dosage. Pirimiphos-methyl (50% EC) was tested for its efficacy in cesspits and drains against the immatures of Cx. quinquefasciatus at Puducherry, an endemic area for filariasis, south India.
In cesspits, Pirimiphos-methyl (50% EC) was tested at the dosage of 25, 50, 100 and 200 g(ai)/ ha and in drains at 50, 100 and 200 g(ai)/ha. Immature density during pre-treatment and post-treatment periods was recorded and the efficacy was determined by calculating percentage reduction in larval and pupal densities for a period of about one month.
In cesspits, application of the insecticide at 25 and 50 g(ai)/ha reduced the density of larvae by >80 per cent for 2-4 days only, whereas at 100 and 200 g(ai)/ha, the efficacy lasted for 7-8 days. More than 80 per cent reduction was observed in pupal density for 4 days at 50 g(ai)/ha and for 10-12 days at 100 and 200 g(ai)/ha respectively. In drains treated with 50 g (ai)/ha, >or=80 per cent reduction in larval density was recorded up to 3(rd) day post-treatment. The efficacy showing >or=80 per cent reduction in larval density lasted for 12-13 days and the same in pupal density lasted for 10-12 days at 100 and 200 g(ai)/ha.
INTERPRETATION & CONCLUSION: At the dosages of 100 and 200 g(ai)/ha, pirimiphos-methyl (50% EC) showed no difference in the control of larvae of Cx. quinquefasciatus in cesspits and drains. Pirimiphosmethyl may be applied at the field dosage of 100 g (ai)/ha at 10 day-intervals in the larval habitats of Cx. quinquefasciatus to achieve >80 per cent reduction in immature density.
甲基嘧啶磷是一种有机磷杀虫剂，已知它可以克服蚊子对其他有机磷的抗药性机制。关于甲基嘧啶磷（50%可乳化浓缩物）控制致倦库蚊幼虫的效果持续时间的信息很少，因此需要进行现场特定的现场试验来确定现场剂量。在印度南部的一个流行区——本地治里，对致倦库蚊幼虫的幼虫进行了测试，以确定其在污水坑和排水沟中的效果。
在污水坑中，以 25、50、100 和 200 g（ai）/ha 的剂量测试了甲基嘧啶磷（50% EC），在排水沟中以 50、100 和 200 g（ai）/ha 的剂量测试了甲基嘧啶磷（50% EC）。在处理前和处理后期间记录了幼虫密度，并通过计算幼虫和蛹密度减少的百分比来确定一个月左右的效果。
在污水坑中，以 25 和 50 g（ai）/ha 的剂量施用该杀虫剂，幼虫密度仅减少了> 80%，持续 2-4 天，而以 100 和 200 g（ai）/ha 的剂量，效果持续了 7-8 天。以 50 g（ai）/ha 的剂量处理时，蛹密度减少了> 80%，持续了 4 天，以 100 和 200 g（ai）/ha 的剂量处理时，持续了 10-12 天。在以 50 g（ai）/ha 处理的排水沟中，处理后 3 天内幼虫密度减少了> 80%。以 100 和 200 g（ai）/ha 的剂量处理时，幼虫密度减少了> 80%，持续了 12-13 天，蛹密度减少了> 80%，持续了 10-12 天。
以 100 和 200 g（ai）/ha 的剂量，甲基嘧啶磷（50% EC）在污水坑和排水沟中对致倦库蚊幼虫的控制没有差异。在致倦库蚊幼虫的幼虫栖息地中，甲基嘧啶磷可以以 100 g（ai）/ha 的田间剂量每 10 天施用一次，以达到幼虫密度减少> 80%。
