An immersion test for screening chemicals for molluscicidal activity against Oncomelania nosophora snails and a modification of the McMullen plate test are described. Results of screening 89 compounds by these methods are given. Twenty-four compounds had an LD50 of less than 0.1 mg (5 ppm) by the immersion test and 0.2 mg (100 ppm) by the plate test. Sodium pentachlorophenate and dinitro-o-cyclohexylphenol were control chemicals. It is believed that the immersion test eliminates several variables inherent in the plate test and that it is preferable for screening of molluscicides in the laboratory.
Captain, U. S. Army. Present address: Walter Reed Army Institute of Research, Walter Reed Army Medical Center, Washington 12, D. C.
Lt. Col., U. S. Army. Present address: Sixth Army Area Laboratory, Ft. Baker, California.