[Molluscicidal effect of buried niclosamide sustained-release method in plateau mountainous areas].

OBJECTIVE: To evaluate the molluscicidal effect of the buried niclosamide sustained-release method in Oncomelania snail-infested terraced environments of mountainous areas in Yunnan Province. METHODS: A piece of relatively isolated snail-infested terraced environment was selected as experimental plot and randomly divided into four groups. The buried niclosamide sustained-release methods were performed in Group A, B, C with the doses of 6 g/m2, 12 g/m2, 24 g/m2 respectively, and Group D was sprayed with 50% niclosamide ethanolamine salt wettable powder (2 g/m2) as the control. RESULTS: In Group C (with the buried niclosamide sustained-release method of 24 g/m2), the half-year reduction of living snail density was 89.90%, and one-year reduction of living snail density was 96.80%, which were significantly higher than those of Group D (40.35% and 59.11%) (Both P < 0.01) CONCLUSION: The buried niclosamide sustained-release method is effective and suitable for snail control in mountainous terrace areas.

[Molluscicidal effect of WPN and MNSC on Lymnaea].

OBJECTIVE: To evaluate the molluscicidal effect of wettable powder of 50% niclosamide ethanolamide salt (WPN) and suspension concentrate of 26% metaldehyde and niclosamide (MNSC) on Lymnaea. METHODS: WPN and MNSC were prepared as a series of solutions containing the active ingredient concentrations of 0.06, 0.13, 0.25, 0.50, 1.00, 2.00 mg/L and 4.00 mg/L, and the adult Lymnaea snails were soaked in the above mentioned series of solutions in the laboratory, and the LC50 values were calculated. The doses of active ingredient concentrations of 0.03, 0.06, 0.13, 0.25, 0.50, 1.00 g/m2 and 2.00 g/m2 of WPN and MNSC were adopted to spray on Lymnaea snails in the laboratory, and the LC50 values were calculated. A series of solutions containing the active ingredient concentrations of 1.00 mg/L, 0.50 mg/L, 0.25 mg/L, and 0.13 mg/L of WPN and MNSC were prepared, and the adult Lymnaea snails were put into the bowls with each concentration solution above mentioned and the climbing situation of the snails was observed at different time. RESULTS: By the immersion method, LC50 values of WPN at 48 h and 72 h were 0.93 mg/L and 0.64 mg/L respectively; LC50 values of MNSC at 48 h and 72 h were 0.74 mg/L and 0.51 mg/L respectively; by the spray method, when active ingredient concentrations of WPN and MNSC were 1.00 g/m2 or more, the death rates were both 100% after 3 days. In the climbing test, the Lymnaea snails did not climb in the solutions containing the active ingredient concentration of 1.00 mg/L of WPN and MNSC, however, a few snails climbed in the low concentrations. CONCLUSIONS: WPN and MNSC both have the effect of killing Lymnaea snails and inhibiting their climbing. By using the immersion method in the field, the active ingredient concentration of 2.00 mg/L of WPN and MNSC for 48 h is appropriate; by using the spray method, the active ingredient content of 1.00 g/m2 of WPN and MNSC for 3 days is appropriate.