Natural Enemies Gallery

Decollate Snail

Hosts or Prey

Various snail and slug species especially brown garden snail, Cantareus aspersus =Helix aspersa

Identification

The decollate snail’s spiraling shell is pinkish brown, elongated, and tapered toward the rear. Young snails can have a more pale-colored shell. The shell grows up to 1-3/5 inches (40 mm) long and 5/8 inch (14 mm) in diameter. As the shell grows, the tip breaks off and older whirls of the shell are dropped; only four to seven whirls are retained in older snails. Young snails may retain up to 10 whirls of the shell.

The antennae, head, and foot are blackish to dark olive-gray. They protrude from the shell's wider (front) end, except they are withdrawn into the shell when the snail is disturbed or taking shelter from heat and sunlight. When feeding on the body of a snail or slug, the prey may produce an excessive amount of foamy mucous in an apparent effort to repel the decollate.

The round, whitish eggs occur in topsoil. Eggs of decollate snail have a brittle shell and are 1/12 inch (2 mm) in diameter.

Decollate snails are active mostly at night and during overcast or rainy weather. During the day they hide in liter on the ground and in the top 1 inch of soil.

Life Cycle

Snails are hermaphrodites, having both female and male parts. They are self-fertile, but commonly mate with another decollate before laying eggs. Decollate snail becomes reproductively mature about 10 months after hatching from an egg. Mature females can lay about 200 eggs per year and up to 500 eggs during their lifetime. Eggs are laid singly or in loose clusters in a depression in soil and generally hatch within 10 to 45 days.

Unlike brown garden snail that will climb trees and other objects, the decollate snail lives only in and on litter and soil. Decollates climb only to escape heavy rain or irrigation water.

In addition to snails and slugs, decollate snail feeds some on seedlings, leaves in contact with the soil, and fallen bruised fruit. In citrus where they commonly occur, they have not been observed to feed on citrus leaves or undamaged fruit.

Habitat

Decollate snail occurs at irrigated sites in Central and Southern California. It is legal to purchase and release decollates only in the counties of Fresno, Imperial, Kern, Los Angeles, Madera, Orange, Riverside, Santa Barbara, San Bernardino, San Diego, Ventura, and Tulare. Because of its potential adverse impact on populations of certain endangered and native mollusks, decollate snail should not be released outside of the above counties.

Decollate snail is native to North Africa and the Mediterranean Region. It was inadvertently introduced into Southern California in the 1960s. Because it is a burrowing species and the eggs and snails occur in topsoil, decollate can be spread readily in container plants and soil that are moved.

Commercial Availability

Decollate snails are reared commercially and can be purchased for introduction into certain areas where they may not be present. While not consistently effective, introducing the decollate snail can reduce brown garden snail populations to insignificant levels in 4 to 10 years. Because decollate introductions are legal only in certain counties check with the local office of the county agricultural commissioner or wildlife officials before introducing them.

Do not release decollate snails near where poison baits are used because baits kill both the pest and predator snails. Decollate introductions are compatible with pruning tree skirts (branches that touch the ground) to make it more difficult for brown garden snails to attack low-hanging fruit. Decollates can be used in combination with applying trunk barriers; for example, copper foil or an effective copper compound (e.g., Bordeaux mixture) can be applied to trunks to exclude and repel snails that climb. Decollate snails generally do not climb trees, thus they will not be affected by skirt pruning or trunk barriers.

For detailed recommendations on snail control and decollate introductions in commercial agriculture, consult the online UC IPM Pest Management Guidelines: Citrus.

More Information

Scientific classification:

  • Phylum: Mollusca
  • Class: Gastropoda
  • Order: Stylommatophora
  • Family: Subulinidae
Adult decollate snail, Rumina decollata, a predator of snail pests.
Adult decollate snail, Rumina decollata, a predator of snail pests. Credit: Jack Kelly Clark, UC IPM Program
Eggs of decollate snail, Rumina decollata, placed unnaturally close together to be photographed.
Eggs of decollate snail, Rumina decollata, placed unnaturally close together to be photographed. Credit: Jack Kelly Clark, UC IPM Program
Adult decollate snail, Rumina decollata (bottom), feeding on a brown garden snail, Cornu aspersum.
Adult decollate snail, Rumina decollata (bottom), feeding on a brown garden snail, Cornu aspersum. Credit: Jack Kelly Clark, UC IPM Program
Remnant shells of beneficial, predatory decollate snails, Rumina decollata, killed by pesticide bait.
Remnant shells of beneficial, predatory decollate snails, Rumina decollata, killed by pesticide bait. Credit: Jack Kelly Clark, UC IPM Program
Appearance and relative size of adult decollate snail, Rumina decollata.
Appearance and relative size of adult decollate snail, Rumina decollata. Credit: David Kidd