Trials with a new molluscicide

A description is given of laboratory and field trials with a new molluscicide, Bayer 73. Following successful laboratory trials at one part per million, a river containing much vegetation and many semi-stagnant pools was treated at this dosage, the application resulting in a complete disappearance of snails and eggs for a minimum distance of 3 miles below the point of application. It is suggested however that caution must be exercised in assessing the results of molluscicide treatments as the usual population sampling techniques may have serious defects at low population densities. The malacological field data are supported by chemical analyses. Further trials are planned as there is evidence that the dosage employed was excessive.