Wrinkled dune snail (Candidula intersecta)

Synonyms: Helix intersecta, Helicella intersecta, Trochoidea intersecta, Cernuella intersecta

Common Names: Wrinkled snail

Description:

Wrinkled dune snail (Candidula intersecta) is a small land snail from western Europe, named for the fine wrinkled ribbing on its pale shell [1][2]. It hitchhikes to new places on plants, soil, stone, and farm goods, and it is a crop pest that feeds on grains and fruit and gathers in large numbers [1][2]. MISIN tracks it as a watch species ? a quarantine-significant pest that is not yet widespread here, where the goal is to catch and report it early before it establishes [1][2].

Identification:

The wrinkled dune snail is small ? its rounded shell is only about 7 to 13 millimeters across (roughly a quarter inch to a half inch), pale white to cream or yellowish, and often marked with brown bands or spots [1][2]. The shell surface has fine ribs or wrinkles, which give the snail its name, and there is a small navel-like opening (umbilicus) in the center of the underside [2]. The soft body is pale yellow to blue-gray [1]. Because it is so small and pale, it is easy to overlook, and it is most often noticed when many gather together [2].

This snail is easiest to find in fall, when cooler, wetter weather brings the snails out to mate and feed, and they often climb plants, fence posts, and walls and cluster in groups [1]. Look for the small pale shells in dry, open, sunny places and on or near crops and nursery plants [1][2].

At-a-glance cues:

1. Small rounded shell, about 7?13 mm (??? inch) across [1][2]
2. Pale white to cream shell, often with brown bands or spots, and a fine ribbed or wrinkled surface [1][2]
3. A small navel-like opening in the center of the shell's underside [2]
4. Often found clustered on plants, posts, or walls in dry open areas, especially in fall [1]

Habitat:

The wrinkled dune snail lives in dry, open, sunny places. Look for it in pastures, grasslands, sand dunes, coastal flats, roadsides, field edges, and farm fields, as well as on nursery plants and around stone and building materials [1][2]. It handles dry conditions well and often climbs up plants, posts, and walls to get off the hot ground [2].

The snail is native to western Europe [1][2]. It has been carried to other parts of the world, including North America, New Zealand, and Australia, where it is treated as a pest of quarantine concern [2]. In the MISIN region it is a watch species ? the priority is to find and report it early, before it becomes established [1].

Reproduction:

The wrinkled dune snail spreads almost entirely by hitchhiking. It and its eggs travel on potted nursery plants, cut flowers, soil, and on stone, marble, tile, and quarry products, as well as on farm machinery, containers, and vehicles ? anything moved from an infested area [1][2]. Because the snails are small and pale and often tuck into crevices, they are easily moved without notice [2].

Each snail is hermaphroditic, meaning it has both male and female parts, so any two adults can mate ? and a lone snail is enough to start a population once eggs are laid [1]. They typically mate and lay their eggs in the soil in autumn, as the weather turns cooler and wetter [1]. For control, fall is both the easiest time to spot the clustering snails and the key time to stop them before eggs are laid (see Management) [1].

Impact and Damage:

The wrinkled dune snail is not a danger to people or pets ? the harm is to crops and trade [2]. On a property with a garden or orchard, it feeds on the seeds and seedlings of grains and on fruit trees such as apple, pear, plum, and peach, and it can damage fruit while it is still on the tree, opening the door to rots and other infections [1][2]. It can also gather in very large numbers [2].

That habit of clustering is what makes it a serious farm and trade pest. Large numbers of snails contaminate harvested grain and produce ? clogging and fouling the harvest ? and snails packed into stored grain can bring fungal growth that spoils it [1][2]. Because it damages crops and rides along in shipped goods, it is listed as a quarantine pest, and keeping it from spreading on plants and materials is the main goal [1][2]. Non-native land snails like this one are also treated as regulated plant pests in the United States ? confirm the specific federal status before relying on it [2].

Similar species:

White garden snail (Theba pisana) is another small, pale, banded land snail from Europe that is a serious invasive pest. It is generally a bit larger, with a more globe-shaped shell and fine brown bands, and it also clusters in large numbers on plants and posts.

Maritime garden snail (Cernuella virgata), sometimes called the vineyard snail, is a closely related small pale snail with brown banding. It is told apart by close shell examination and is likewise an invasive crop and grain-contaminating pest.

Heath snail (Xerolenta obvia) is a similar small whitish snail with brown bands that also lives in dry, open grasslands and roadsides. These small pale "dune and heath" snails are difficult to tell apart in the field and often need an expert to identify with certainty.

Monitoring and rapid response:

Signs to watch for:

1. Small pale, brown-banded, ribbed snail shells (about ??? inch across) in dry, open areas or on crops and nursery plants [1][2]
2. Snails clustered on plants, fence posts, or walls, especially in fall [1]
3. Snails or empty shells turning up on shipped plants, soil, stone, or tile [2]

What you can do:

1. Inspect new plants, pots, soil, mulch, stone, and tile for small snails and shells before bringing them home, and destroy any you find [1][2].
2. Hand-pick snails ? easiest in fall when they cluster ? and kill them by dropping them in soapy water or sealing them in a bag for the trash [1].
3. Do not move soil, plants, or garden and building materials from an area where these snails occur, and clean soil and debris off shoes, tools, and vehicles [1][2].
4. Because this is a quarantine-significant pest, report any suspected find (below) and to your state agriculture department so it can be confirmed and tracked [1][2].
5. Natural area crews, growers, and shippers should monitor high-risk pathways ? nurseries, quarries, and incoming shipments ? and coordinate with the state plant-health program on any detection [2].

When to call a professional:

1. Any suspected wrinkled dune snail, especially on crops or in shipped goods ? contact your state department of agriculture or plant-health program, since it is a regulated quarantine pest and identification should be confirmed [1][2].
2. For chemical control options, contact a licensed applicator or your local cooperative extension office.

Report sightings to MISIN. Help track this species' spread by submitting observations through the MISIN web site or the MISIN mobile app (Android, iOS, Windows, and macOS). Photos at multiple angles paired with a precise GPS location are the most valuable data for confirming new occurrences and triggering rapid-response review.

Credits:

1. Michigan Department of Natural Resources. Invasive Species: Wrinkled Dune Snail (Candidula intersecta). michigan.gov/invasives
2. CABI. Candidula intersecta (wrinkled dune snail) ? Invasive Species Compendium. semanticscholar.org

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