Photo: The snail-killing decollate snail
Snails and slugs have many natural enemies including ground beetles, pathogens, snakes, toads, turtles, and birds, but most are rarely effective enough to provide satisfactory control in the nursery. One predator found in some California gardens is a large Staphylinid beetle called the devil’s coach horse, Ocypus olens. However, this beetle, which is more than 1-inch long, also will feed on ripening or decaying fruits and vegetables.
Domesticated fowl—such as ducks, geese, or chickens—kept penned in infested areas can be effective snail predators that significantly reduce problems. Be careful, though, as these birds also can eat seedlings.
The predatory decollate snail, Rumina decollata, has been released in Southern California citrus orchards to control young brown garden snails and may be providing effective biological control. It feeds only on small snails, not full-sized ones. Because of the potential impact of the decollate snail on certain endangered mollusk species, it can’t be released in California outside of Fresno, Imperial, Kern, Los Angeles, Madera, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, Ventura, and Tulare counties. Decollate snails can feed on seedlings, small plants, and flowers and can be a nuisance when they cover the back patio on a misty day. Because snail baits will kill decollate snails, you shouldn’t use them where these predators are active. Also, nurseries with a “snail-free” designation should not use decollate snails since any snail found in a shipment is cause for rejection.
Nematodes are small microscopic worms and some species are known to kill snails and slugs. One species called Phasmarhabditis hermaphrodita is currently being used as a biological control agent in Europe but because this nematode has not been found in North America it cannot be used in the U.S.
The information in this section has been modified from the University of California IPM website (http://www.ipm.ucanr.edu/).