SUMMARY: Sodium 2,5-dichloro-4-bromophenol named B-2 was evaluated for application in the field as a molluscicide against Oncomelania nosophora. A dosage of 10 g/m2 as 25% liquid form or 25 g/m2 as 10% granular form of B-2 was suggested as a standard dose for the control of O. nosophora. The residual concentration of B-2 in the soil after application was observed to decrease more rapidly than did that of NaPCP. The residual level of B-2 in the rice grains harvested from the paddy field in which the chemical was applied at most 4 times during the planting season did not exceed 0.03 ppm.

SUMMARY: Laboratory trials of sodium 2 ,5 dichloro-4-bromophenol named B-2 f or the molluscicidal effect against Oncomelania nasophora were carried out by Komiya's immersion technique. The values of LC50 of B-2 varied from 0 .38 ppm to 0 .54 ppm depending on the collection time of the snail . They were almost equal to those of NaPCP, but lower than those of Niclosamide . In the tests of toxicity to carp, rainbow trout and killifish , B-2 showed lower toxicity than NaPCP. Some aspects of mollusciciding application of the chemical were discussed .