[Molluscicidal effect of LDS in mountainous areas of Yunnan Province].

ABSTRACT

OBJECTIVE: To observe the molluscicidal effect of a novel molluscicide, salt of quinoid-2', 5-dichloro-4'-nitrosalicylanilide (LDS) on Oncomelania hupensis in laboratory and field of mountainous areas of Yunnan Province. METHODS: With the immersion method, 10% LDS with concentrations of 0.1, 0.2, 0.4, 0.6, 0.8 mg/L was tested, and 50% niclosamide (WPN) with the concentration of 2 mg/L as well as fresh water were tested as the controls. The molluscicidal effects of 24, 48, 72 h were observed in lab and the field. With the insufflation method and powdering method, 10% LDS with doses of 0.2, 0.4, 0.6, 0.8, 1.0 g/m2 was tested and 50% WPN with the dose of 2 g/m2 as well as fresh water were tested as the controls. The molluscicidal effects of 1, 3, 7 d were observed in lab and the field. RESULTS: At the room temperature of 25-26 degrees C and water temperature of 21-22 degrees C, when exposed for 72 h by the immersion method, the snail death rates of above-mentioned five concentrations of LDS and WPN as well as fresh water were 93.33%, 100%, 100%, 100%, 100%, 100% and 6.67%, respectively in lab. At the field temperature of 18-28 degrees C and water temperature of 18-23 degrees C, when exposed for 72 h by the immersion method, the snail death rates of above-mentioned five concentrations of LDS and WPN as well as fresh water were 91.11%,100%,100%, 100%, 100%, 100% and 3.33%, respectively in the field. When exposed for 7 d by the insufflation method, the snail death rates of five above-mentioned dosages of LDS and WPN as well as fresh water were 90.00%, 94.00%, 96.00% 99.00%, 99.00%, 94.00% and 6.00%, respectively in lab and 80.00%, 82.14%, 88.35%, 90.83%, 96.55%, 92.56% and 4.55%, respectively in the field. When exposed for 7 d by the powdering method, the snail death rates were 74.77%, 88.89%, 94.50%, 90.38%, 92.17%, 90.38% and 4.55%, respectively in the field. CONCLUSION: LDS has a good molluscicidal effect on Oncomelania hupensis in mountainous areas.