Abstract: Objective To evaluate the molluscicidal effect of 60% metaldehyde water dispersible granules(MWG) against Oncomelania hupensis snails in laboratory and field settings. Methods By the standard procedures specified in Efficacy Test Methods and Evaluation of Molluscicide for Pesticide Registration(NY / T 1617-2008), we conducted the experiment in both laboratory and field setting using MWG against the snails via immersing and spraying methods. Then the mulluscicidal effect was compared with that of 50% wettable powder of niclosamide ethanolamine salt ( WPN ). Results In the laboratory, LC50(s) at 1, 3 and 7 d was 0. 312(0. 271~0. 360), 0. 216(0. 190~0. 245)and 0. 177(0. 160~0. 196) g /m² , respectively, by MWG immersing. The mortality rate of snails was 98. 00% by spraying MWG for 7 days in dose 0. 900 g / m² in the laboratory setting, and respectively 90. 91% and 85. 12% by the identical protocol applied to the field settings at grass beaches and flood plains in Yueyang and Jiangling County. The difference was insignificant for the mortality rate of snails when comparing the dosage of 50% WPN (1. 000 g / m² ) with that of 60% MWG (0. 900 g / m² and 1. 800 g / m² administered at the grass beaches in Yueyang County, χ² = 2. 555, 3. 340; P > 0. 05, respectively) and (1. 800 g / m² administered at the flood plains in Jiangling County (χ² =0. 989, P>0. 05). Conclusion Spraying 60% MWG in dose of 0.900 g / m² in both laboratory and field setting can lead to the requirements specified in Efficacy Test Methods and Evaluation of Molluscicide for Pesticide Registration, which suggests that this protocol may be a novel and potent molluscicide with easy performance.

Key words: Metaldehyde WG, Water dispersible granule, Molluscicidal effect, Oncomelania hupensis