Common Garden Snail

Helix aspersa

Family: Helicidae

Order: Eupulmonata

Class: - Gastropoda

Description:

Adult - The shell is over 30 mm

Colour - The shell is brown usually with alternating lighter brown spiral stripes. The body is dark grey.

Body - Soft and slimy body enclosed within a hard spiral shell.

Mouthparts -

Antennae - 2, retractable

Legs - None

Egg - Spherical, pearl white, 4 mm diameter. Usually about 40 mm deep in moist soil.

Habits - Leaves a silver trail.

Biology:

The shell is made of calcium carbonate (limestone) and covered with a protein coat that provides the distinctive colours and patterns.

The body remains moist making them susceptible to dehydration.

They produce a mucous slime when they move leaving a typical silver snail trail.

They are mainly active during damp weather when temperatures are 15-25 degrees C. They are less active during heavy rain and in high winds.

They are hermaphrodites, all individuals may lay eggs. Mating usually takes place in mid autumn to mid winter. The eggs are laid into moist soil and cannot survive dry periods.

Life Cycle:

They seal themselves inside their shell and aestivate in summer. With cooling temperatures and autumn rains they become active and mate. 2-4 weeks later they dig a small hole about 40 mm deep in moist soil and lay 20-120 eggs. The eggs hatch in 2-4 weeks and the young snails emerge to feed.

Habitats:

Mainly found in cultivated and irrigated areas with introduced plants. Rarely found in bushland.

They hide in shady protected areas.

Origin and History:

Mediterranean.

Distribution:

Widespread. Significance:

Significance:

Beneficial:

Edible and the most widely farmed species in France.

Detrimental:

This is the main urban pest snail species.

Major pest of ornamentals.

Damages a wide range of seedlings and vegetables.

Damages citrus fruit, leaves and young shoots.

Feeds mainly on the leaves of grape vines and deciduous fruit trees but may occasionally damage young fruit.

Damage is usually irregular pieces missing from the leaf edges or the removal of cotyledons in broad leaved crops resulting in plant death. Damage can be difficult to see if seedlings are being chewed down to ground level as they emerge.

Management and Control:

Baits are often used.

A combination of cultural, chemical and biological control are usually required to provide control.

Graze or burn stubble to remove refuges.

Kill summer and autumn weeds and plants along fence lines to reduce food supplies and refuge areas.

Burn in autumn to kill surface dwelling species.

Monitor paddocks for snails in autumn before planting and lay baits early before egg laying commences in autumn.

Use fortnightly applications of baits at lower rates (e.g. 5 kg/ha) rather than a single high rate of bait.

Bait refuge areas such as fence lines.

Use control options that minimise damage to biological control agents such as Ground Beetles.

Avoid liming paddocks as this aids survival of the snails.

Spring baiting is often ineffective because many populations are relatively immobile juveniles and there is ample alternative feed.

Replant areas of broad leaved crops that have been damaged at emergence.

Related Species:

Green Snail (Helix aperta) has a smaller, green to brown shell that is uniform in colour. When young they have a cream rather than dark grey body.

Similar Species:

References:

CSIRO. The Insects of Australia. Melbourne University Press. (1991)

WADA. Insects and Allied Pests of Extensive Farming. Department of Agriculture - Western Australia Bulletin No. 4185.

Avidov, Z. and Harpaz, I. (1969) Plant Pest of Israel. Israel University Press. P

1316

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.