Laboratory and field trials of a slow-release copper molluscicide in St. Lucia

Tests of a slow-release molluscicide containing 50% copper sulfate were under-taken in laboratory and field situations in St. Lucia. In laboratory trials, a granule form of the molluscicide produced 100% mortality of Biomphalaria glabrata down to 4 mg/liter active ingredient (a.i), while the pellet form produced 100% mortality down to 8 mg/liter a.i. In field trials, a dose of 100 mg/liter a.i. in granule form caused mortality of B. glabrata in banana drains but had no effect on B. glabrata populations in a marsh habitat. In both habitats, the dose of 100 mg/liter produced mortality of other molluscan fauna which caused changes in the molluscan diversity indices. This failure in field trials may have been due to dilution of copper levels caused by flooding and also by uptake of copper by mud and algae.