关键词: 钉螺, 吡螺脲, 灭螺效果, 鱼毒性

Abstract: Objective　To evaluate the molluscicidal effect of 25% wettable powder of pyriclobenzuron sulphate (WPPS) against Oncomelania snails in hilly schistosomiasis⁃endemic regions and test its toxicity to fish. Methods　In October 2020, a snail⁃infested setting which had been cleared was selected in Nanjian County, Yunnan Province and divided into several blocks, and the natural snail mortality was estimated. 25% WPPS was prepared into solutions at concentrations of 1 and 2 g/L, and 25% wettable powder of niclosamide ethanolamine salt (WPNES) was prepared into solutions at a concentration of 2 g/L. The different concentrations of drugs were sprayed evenly, and the same amount of water was used as blank control. Snails were surveyed using the systematic sampling method 1, 3 and 7 days post⁃treatment, and snail survival was observed. A fish pond was selected in Nanjian County, and 2 kg 25% WPPS was evenly sprayed on the water surface to allow the effective concentration of 20 g/L. Fish mortality was estimated 8, 24, 48 and 72 h post⁃treatment. Results　One⁃day treatment with 1 and 2 g/L WPPS and 2 g/L WPNES resulted in 97.99%, 97.99% and 94.11% adjusted snail mortality rates ([χ2] = 3.509 and 3.509, both P values > 0.05）, and the adjusted snail mortality was all 100% 3 d post⁃treatment with 1 and 2 g/L WPPS and 2 g/L WPNES, while 7⁃day treatment with 1 and 2 g/L WPPS and 2 g/L WPNES resulted in 91.75%, 86.57% and 57.76% adjusted snail mortality rates （[χ2] = 14.893 and 42.284, both P values < 0.05）. Treatment with 2 g/L WPPS for 72 h resulted in a 0.67% cumulative mortality rate of fish. Conclusion　25% WPPS is effective for snail control and highly safe for fish, which is feasible for use in hilly schistosomiasis⁃endemic regions.

Key words: Oncomelania snail, Pyriclobenzuron, Molluscicidal effect, Fish toxicity