Review of the efficacy and persistence of pyriproxyfen 0.5% granules on Anopheles sp. and Aedes sp. breeding sites in Sri Lanka

Abstract:
The insect growth regulator, pyriproxyfen (Sumilarv 0.5 G) at the rate of 0.01 mg a.i./L was applied to gem pits as well as river and stream bed pools as a part of a large scale trial in a gem mining area in Sri Lanka. The results indicated pyriproxyfen inhibited emergence of the primary malaria vector, Anopheles culicifacies adults in gem pits and river bed pools for 185 and 190 days respectively and significant reduction of incidence of malaria. A small scale trial showed that two annual treatments with pyriproxyfen at the rate of 0.01 mg a.i. /L would be cost effective. Twelve villages were determined to be the major breeding places of the primary vector and secondary vector, An. subpictus. Pyriproxyfen was applied at the rate of 0.01 mg a.i. /L to the vector breeding places of the treatment villages. The treatment caused significant reduction of the adult An. culicifacies (78%) and An. subpictus (72%). Similarly incidence of malaria (70%) was reduced in the treatment villages. Ground level domestic water storage cement tanks are one of the important breeding sites of Aedes aegypti and Aedes albopictus. Small scale field trial was carried out using the 1000 liter capacity unwashed tanks to assess the efficacy of 0.001 ppm, 0.1 ppm of pyriproxyfen and 1 ppm temephos 1% granules. Results indicated the inhibition of emergence of adults up to 40, 57 and 56 days respectively. Data from similar field bioassays using 0.01 ppm pyriproxyfen and 1ppm temephos, but with washing of tanks after 14 days and refilling of the tanks showed 100% emergence inhibition up to 22 days and 15 days respectively. Other breeding places were treated with a combination of temephos 50 EC and pyriproxyfen 0.5% granules at the rate of 0.111 kg a.i. /ha and 0.01mg a.i. /L respectively. The results to date indicate pyriproxyfen inhibits mosquito adult emergence for at least one month.