Evaluation on molluscicidal effect of suspension concentrate of metaldehyde and niclosamide

OBJECTIVE: To evaluate the molluscicidal effect of suspension concentrate of 26% metaldehyde and niclosamide (MNSC) in laboratory and field. METHODS: The experiment of MNSC against Oncomelania snails were performed by immersion and spray methods with different time in laboratory and field, and the wettable powder of 50% niclosamide ethanolamine salt (WPN) and fresh water were set as the controls. RESULTS: In laboratory, by immersion method (immersion for 24 h), LC50 of MNSC was 0.058 3 mg/L, which was lower than 0.094 7 mg/L of WPN. For the concentrations of 2.0 mg/L and 1.0 mg/L of MNSC by immersion method (immersion for 24, 48 h and 72 h, respectively), the death rates of snails were all 100%. In laboratory, by the spray method, the snail death rates were higher than 97% on the 3rd and 7th day when the dosage of MNSC was higher than 1.0 g/m2. In the field, by the immersion method, the snail death rates of MNSC (2 g/m3) for 24, 48 h and 72 h were 97.78% -100% in Hubei Province and 97.50% - 100% in Anhui Province, respectively, the rates of WPN were 98.89% - 100% and 97.56% - 100%, respectively, and the snail death rates of MNSC and WPN were both 100% in Jiangsu Province. In the field, by the spray method, the snail death rates of MNSC for 1, 3 d and 7 d were 83.12% - 94.64% in Jiangsu Province, 67.81% - 86.67% in Hubei Province and 72.80% - 100% in Anhui Province, respectively. The snail death rates of WPN for 1, 3 d and 7 d were 78.40% - 86.11%, 77.27% - 87.50% and 83.81% - 98.51%, respectively. In Hunan Province, the snail death rates of MNSC and WPN after spraying for 7 d were 94.94% and 94.20%, respectively, after spraying for 15 d, the rates were 86.67% and 89.38%, respectively. CONCLUSIONS: The molluscicidal effect of MNSC is as the same as WPN by immersion and spray methods in laboratory and field. MNSC has the characteristics of good water solubility, quick dispersing and easy using. In addition, the efficiency component of MNSC is half of WPN. So MNSC is a novel form of molluscicide which is worthy of promotion in field.