Pistia clearance with herbicides in rural-filariasis control: A preliminary note.

Of a number of herbicides used in Pistia clearance, as a control measure of rural filariasis (Wuchereria malayi) in Ceylon, Phenoxylene 30 (MCPA) and 2,4-D amine salt were found to be the most effective, cheapest, and easiest to handle. 56 ml (2 fluid ounces) of Phenoxylene 30, and 28 ml (1 fluid ounce) of a wetting agent ("Teepol"), were added to 4.2 litres (approximately 1 Imperial gallon) of water, and 163 litres (36 gallons) were sprayed over 4,046 m(2) (1 acre) of water covered with Pistia. It is much more effective to spray young Pistia, which will be killed in about a week. Excellent results were obtained, during a large-scale field experiment, with a single application. The total cost per acre was Rs20, being only one-sixth that of manual removal. The methods of application are described.