Laboratory study on the molluscicidal effect of carbamide.

Objective The study was conducted to establish a molluscicide with strong snail-killing effects and low toxicity to aquatic organisms.Methods Immersion tests using 100,200,400 and 800 mg/L carbamide and spraying tests using 15,20,25 and 30 g/m2 carbamide were conducted under laboratory conditions to measure the molluscicidal effects,respectively,which were then compared to the effect using 2 g/m2 niclosamide.Results The Oncomelania hupensis mortality rates ranged from 3% to 6% after carbamide immersion at the concentration of 100-800 mg/L,suggesting no statistical difference from those in the control group(P0.05).The 1,3 and 5 d O.hupensis mortality rates in laboratory spraying tests reached 91%,90% and 95% in the 30 g/m2 group,while those in the 2 g/m2 niclosamide group were 97%,96% and 98%,indicating no statistically significant difference(P0.05).Conclusion Under laboratory conditions,carbamide immersion was ineffective in killing snails,whereas carbamide spraying had the same molluscicidal effects as niclosamide did.