The molluscicidal properties of Ambrosia maritima L. (Compositae). 2. Results from a field trial using dry plant material.

: A field trial in Egypt of the plant molluscicide, Ambrosia maritima is described. Applications of 140, 70 and 35 mg/l-1 dry, whole plant were made to irrigation canals and drains in June. The treatment effect took between 1 and 5 weeks to become fully established. The reduction in the numbers of alive Biomphalaria alexandrina snails was generally more than 90% and was virtually the same at all treatment levels and in both types of watercourse. The snail population remained at a low level for at least 3 months until September-October. The possible use of a single, annual application in April or May in controlling snails throughout the main schistosomiasis transmission season in Lower Egypt is suggested.