徳島市内におけるメトプレン製剤によるアカイエカ防除に関する野外試験

Abstract

The efficacy of Altosid^[○!R]10F (A 10 F; a slow release formulation containing 10% methoprene) was tested against Culex pipiens pallens larvae and pupae living in four highly polluted ditches in Tokushima. Diluted A 10 F was sprayed on the water surface so that the concentration of methoprene was 0.86-2.27ppm to standing water or 0.34-0.71g/m^2 to the area of water surface. The control effect was evaluated by measuring the corrected emergence inhibition rate (CEIR). The effect of methoprene appeared in pupae and 4th instar larvae collected 0.5hr after spraying and CEIR reached 96-100% in the pupae collected after 24hr. The larvae were immersed in sprayed ditches for 2hr. The adults from those larvae were divided into three groups by the time of their emergence; 0-3,3-13,and 13-24hr. The 3-13hr group was most sensitive to A 10 F. When sprayed into gently flowing ditches, methoprene's relative concentration measured by CEIR of immersed larvae remained higher in the margins than at the center of ditch. The CEIRs at three sprayed ditches remained at 82-100% for one week after the first spray. Following the second spray application carried out one week after the first, the CEIRs remained at 81 and 100% for 9 days at Jonan and Tomitabashi, and 88-100% for 16 days at Okinohama I, and sectors of the ditch downstream from the experimental one also showed reduction in mosquito emergence due to A 10 F. The period showing more than 70% CEIR was 10 days after the second spray application at Jonan-1 (78m downstream), 11 days at Jonan-2 (112m downstream), 10 days at Jonan-3 (153m downstream) and 11 days at Jonan-4 (191m downstream). High CEIRs persisted for 16 days after the second spray application at Okinohama-1 (84m and 37m downstream from the application sites). A similar high level was registered on day 54.