Theba pisana (OF Müller, 1774)

Cornu aspersum (OF Müller 1774)

Snails, Pisa snail, squirrel

Two main species of snails can be harmful to the vineyard.

• Damage and nuisance

These gastropods are polyphagous, nocturnal, hibernating on the ground then climbing on the vines as soon as the temperatures warm, especially if the spring is wet (figure 1). These pests will then consume the young shoots during bud break (figure 2). On older leaves, snails attack the leaf blades but leave the veins. The damage can be significant during the rainy season. The protective sleeves for young vines promote their concentration.

• Description of pests

• Theba pisana (pink caragouille or small white snail or Pisa snail) has a white shell measuring 12 to 25 mm in diameter and decorated with more or less marked brown bands.
  • Cornu aspersum squirrel ( snail) is larger, 30-40 mm in diameter, and the shell is golden-brown with dark ornamentation (Figure 3).

• Life cycle, population dynamics

Snails are hermaphrodites. The eggs (Figure 4) are laid in groups in a hole in the ground from late spring to late summer. Hatching occurs about a month later and gives rise to a miniature adult which gradually grows with its shell. The speed of development is more or less rapid depending on the species, 4 to 5 months for Theba pisana , more than a year for Cornus aspersum .

During the winter, the snail remains in its shell, sealing it with its mucus forming a kind of operculum which will be pierced when activity resumes in the spring. In ungrassed plots when the vines are budding, snails are more of a problem because they are looking for food. The distribution of these pests is in foci, but they are not always visible because of their nocturnal activity.

• Protection methods

Collecting snails, once used, is a very time-consuming and often insufficient method. Copper known for its repellent action is effective too late because it is only used for foliar treatments. Molluscicides should be used before bud break when the snails are not yet mounted on the vines. For information, there is a national observatory , operating with a network of trappers, making it possible to anticipate the first risks.

In addition, there are beetles living on the ground, predators of snails, such as the glowworm Lampyris noctiluca (Linnaeus 1767) (Lampyridae, photo), ground beetles (Carabidae, photo), or the larva of Drilus flavescens , GA Olivier 1790 (Drilidae) that thrives in the shell feeding on the pest (photo).

Among small animals, the common hedgehog <em> Erinaceus europaeus </em> L 1758, is a remarkable predator of snails (photo). However, this species protected in France, which mainly nests in hedges and bushes, tends to leave the agricultural environment and take refuge in urban areas. We can promote its installation on the plots by arranging nesting boxes (piles of wood).

Bibliography

Delbac L, Davidou L, Rouzes R (2015) Secondary vine pests . Union Girondine des Vins de Bordeaux, special issue, April, 65-68

Classification : Animalia, Mollusca, Gastropoda, Pulmonata, Helicidae
New species : Helix aspersa ( C. sprinkling )

English name : vine snail, white garden snail ( T. pisana ), garden snail ( C