Absence of residues from crops irrigated with water treated with trifenmorph for schistosomiasis control.

The fate of the molluscicide trifenmorph (N-tritylmorpholine) following its use in irrigation systems to control the intermediate hosts of schistosomes was studied by laboratory and field experiments. Laboratory studies with (14)C-trifenmorph indicated that bean plants did not take up detectable residues when the soil in which they were grown was irrigated with water containing trifenmorph in concentrations likely to occur in the field. These laboratory studies have been complemented by field irrigation studies of growing crops in southern Africa and the Sudan. Residues of trifenmorph and its breakdown product triphenylmethanol could not be detected in the crops and the limit of detectability was 0.01-0.02 ppm. These results indicate that residues are not likely to be present in irrigated crops following the treatment of the irrigation water systems with trifenmorph.