[Molluscicidal effect comparison between TDS and MNSC in field].

OBJECTIVE: To compare the molluscicidal effects between "Luo-wei" (TDS), a plant molluscicide in 4 percent, and metaldehyde and niclosamide (MNSC) in the field. METHODS: A natural ecological environment with Oncomelania hupensis was selected as the test area, the test concentrations of TDS and MNSC were 2.5 g/m3 and 2 ml/m3 respectively by the immersion method; the test doses of TDS and MNSC were 3 g/m2 and 2 ml/m2 respectively by the spray method; the doses of WPN in a control group were 2 g/m3 and 2 g/m2 respectively by the two methods above-mentioned. The molluscicidal effects between TDS and MNSC were compared by using the synchronous design method and parallel comparative method. RESULTS: In the TDS group, the death rate of snails was 90.70% by immersion for 24 hours, reached to 81.40% after spraying for 7 days, and there were no significant differences among the observation time points in molluscicidal effects (P > 0.05). One day after the spraying, the death rate of snails was less in the TDS group compared with that in the MSCN group (P < 0.01), but the death rates of snails were similar in both groups 3 days after the spraying (P > 0.05). In the MSCN group, the death rate of snails was 99.17% by immersion for 24 hours, reached to 66.07% by spraying for 1 day. In the WPS group, the death rate of snails was 97.15% by immersion for 24 hours, reached to 71.43% after spraying for 1 day, and there were no significant differences (both P > 0.05). CONCLUSION: TDS has a good molluscicidal activity and stable efficacy, and the molluscicidal effect of TDS is similar to that of MSCN in the filed, but the molluscicidal sensitivity of TDS is lower than that of MSCN.

[Molluscicidal effect of plastic film mulch covering method].

OBJECTIVE: To evaluate the molluscicidal effect of the plastic film mulch covering method. METHODS: In the barren land with a lot of Oncomelania hupensis snails, 3 experimental groups were set up, in which respectively using 3 different methods: a simple plastic film mulch covering method, film assisted with ammonium bicarbonate, and film assisted with amine molluscicide. In the canals, two experimental groups were set up, in which respectively using 2 different methods: simple plastic film mulch covering method and film assisted with ammonium bicarbonate. In above-mentioned areas, obstacles were cleared artificially. In each experiment group, 4 observation spots were set up, and 100 living snails were pot in each spot, and then, the plastic film mulch was evenly covered. The status of the snails was observed 3, 7, 15 and 30 days after the intervention. RESULTS: In the barren land, the snail death rates of the simple plastic film group were 20.77% and 96.92% 15 days and 30 days after the intervention, respectively. The snail death rate of the film assisted with amine molluscicide group was 80.46% 3 days after the intervention. In all the experiment groups, the snail death rates were from 96.92 to 100% 30 days after the intervention. CONCLUSION: The plastic film mulch covering method has a great molluscicide effect in the hill subtype and water network type of schistosomiasis epidemic areas.