Molluscicidal activity of 25% wettable powder of pyriclobenzuron sulphate against Oncomelania hupensis robertsoni

Abstract

Objective To evaluate the molluscicidal activity of a novel molluscicide pyriclobenzuron against Oncomelania hupensis robertsoni in the mountain regions of Yunan Province, and test its toxicity to fish, so as to provide scientific evidence for the extensive application of this molluscicide in schistosomiasis-endemic foci of Yunan Province.

Methods In the laboratory and snail-breeding field of Dali Prefecture, Yunnan Province, the molluscicidal activity of 5% wettable powder of pyriclobenzuron sulphate (25% PBU) against O. hupensis robertsoni was assessed by using the immersion and spraying method, and the acute toxicity of 25% PBU to carp fries was tested, while 25% wettable powder of niclosamide ethanolamine salt (50% WPNES) served as a control.

Results The 1-, 2- and 3-day 25% PBU LC50 and LC90 values were 0.47, 0.25 and 0.23 mg/L, and 1.54, 0.61 and 0.49 mg / L for O. h. robertsoni by using the immersion method in laboratory, and immersion with 25% PBU at 1.0 mg / L for 1 day achieved a comparable molluscicidal efficacy in relative to 50% WPNES at 1.0 mg/L. Spraying with 25% PBU at 4.0 g/m ² achieved 1-, 3- and 7-day snail mortalities of 64.23%, 96.67% and 100.00% in laboratory, respectively, which were not significantly different from those caused by treatment with 50% WPNES at 1.0 g/m ² (all P values > 0.05). One-day field immersion with 25% PBU at doses of 1, 2 and 4 g/m ³ resulted in snail mortalities of 90.00%, 93.33% and 100.00%, respectively, which were not significantly different from those caused by treatment with 50% WPNES at 1.0 g/m ³ (all P values > 0.05), and 3-day field spraying with 25% PBU at doses of 2.0 and 4.0 g/m ² caused snail mortalities of 86.36% and 87.72%, respectively, which were not significantly different from those caused by 50% WPNES treatment (both P values > 0.05). The 24-, 48- and 72-hour LC50 values of 25% PBU to carp fries were 29.38, 24.62 and 23.38 mg/L, respectively, and no fish death was observed within 72 hours of exposure to 25% PBU at a concentration of 17.5 mg/L and lower.

Conclusion 25% PBU is a novel, highly potent and environment-friendly molluscicide that is feasible in fish ponds, and the recommended dose is 1 g/m ³ for field immersion and 2 g/m ² for field spraying in schistosomiasis-endemic areas of Yunnan Province.

Abstract

［摘要］ 目的 评价吡螺脲在云南大山区的杀螺效果和对鱼类的急性毒性, 为该药在云南省血吸虫病流行区推广应用 提供科学依据。 方法 在云南省大理州实验室和有螺现场, 采用浸杀法和喷洒法开展 25% 吡螺脲硫酸盐可湿性粉剂 (25% PBU) 对湖北钉螺滇川亚种的杀灭试验, 并观察对鲤鱼的急性毒性。以 50% 氯硝柳胺乙醇胺盐可湿性粉剂 (50% WPNES) 为药物对照组。 结果 25% PBU 室内浸杀钉螺 1、2 、3 d 的半数致死浓度 (LC ₅₀) 分别为 0.47、0.25、0.23 mg/L, 90% 致死浓度 (LC ₉₀) 分别为 1.54、0.61、0.49 mg/L; 1.0 mg/L 25% PBU 浸杀 1 d 的杀螺效果与 1.0 mg/L 50% WPNES 对照组 相当。4.0 g/m ² 25% PBU 室内喷洒 1、3、7 d 的钉螺死亡率分别为 64.23%、96.67% 和 100.00%, 与 1.0 g/m ² 50% WPNES 杀 螺效果差异无统计学意义 ( P 均 > 0.05) 。1、2、4 g/m ³ 25% PBU 现场浸杀 1 d 后钉螺死亡率分别为 90.00%、93.33% 和 100.00%, 与 1.0 g/m ³ 50% WPNES 浸杀效果差异均无统计学意义 ( P 均 > 0.05) 。2.0 g/m ² 和 4.0 g/m ² 25% PBU 现场喷洒 3 d 后钉螺死亡率分别为 86.36% 和 87.72%, 与 1.0 g/m ² 50% WPNES 灭螺效果差异均无统计学意义 ( P 均 > 0.05) 。25% PBU 对鲤鱼苗 24、48、72 h 的 LC ₅₀ 值分别为 29.38、24.62、23.38 mg/L; 72 h 观察期内, 17.5 mg/L 及以下浓度组未发现鱼苗死亡 现象。 结论 25% PBU 是一种可应用于鱼塘等环境灭螺的生态保护型新型杀螺剂, 其在云南省血吸虫病流行区现场浸 杀灭螺的建议剂量为 1 g/m ³, 喷洒灭螺建议剂量为 2 g/m ²。