Can snails ever be effective and safe biocontrol agents?

The use of snails as biocontrol agents against other snails and against aqu atic weeds is reviewed, evaluating their success and their impacts on non-t arget organisms. The predatory snail Euglandina rosea land other species), although widely used against Achatina fulica (the giant African land snail) on Pacific and Indian Ocean islands, has not been shown to control A. fuli ca but has seriously impacted endemic island species. The facultative preda tor Rumina decollata, used in California against. Helix aspersa (brown gard en snail), is widely considered to be environmentally benign. However, evid ence of its effectiveness is weak and it will also consume native snails. A mpullariid and thiarid freshwater snails have been used as competitors land incidental predators) of snail vectors of human schistosomes, the parasite s causing schistosomiasis (bilharzia). Successful control has been reported but impacts on native biotas have been essentially ignored. Ampullariids h ave been used in attempts to control aquatic weeds, sometimes successfully, but again with little consideration of impacts on native biota. Most snail s have generalist feeding habits. Thus they are inappropriate biocontrol ag ents because of their potential nontarget effects. Rarely has adequate pre- release testing of snails been undertaken and post-release monitoring of no n-target impacts has always been incidental. The use of non-native snails f or biocontrol purposes is poorly regulated; many introductions are unoffici al and sometimes illegal. Use or snails as biocontrol agents, if implemente d, must be based on adequate pre-release testing, post-release monitoring a nd genuine concern for preservation of native biodiversity.