Vineyard Snail

Cernuella virgata

Also called the Common White Snail.

Family: Helicidae

Order: Eupulmonata

Class: - Gastropoda

Description:

Adult - The shell is usually less than 20 mm in diameter.

Colour - The shell is mainly white but often has brown concentric lines. The body is creamy white.

Body - Creamy white, soft and slimy body enclosed within a hard spiral shell.

Umbilicus - Open circular hole.

Mouthparts -

Antennae - 2, retractable

Legs - None

Head -

Thorax -

Abdomen -

Egg -

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:

In spring, they climb posts, plants and other vertical surfaces and aestivate to avoid the hot ground temperatures over summer. They become active again after the autumn rains. 1-2 mm of rain triggers feeding. Mating occurs 2-3 weeks after good autumn rains and lower temperatures and egg laying commences soon after mating. Egg clusters are laid in the top soil from autumn to spring. Eggs hatch about 2 weeks after laying. The juveniles feed in winter and spring and aestivate over summer to become sexually mature at one year old.

Habitats:

Prefers alkaline sandy soils with high calcium content.

Origin and History:

Introduced.

Distribution:

Limited distribution in WA. Suspect snails should be forwarded to the Department of Agriculture for identification.

Significance:

Beneficial:

Detrimental:

Pest of crops, pastures, grapevines and ornamentals.

The major economic damage is usually from feeding on young seedlings.

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. Cereals often recover from early damage whereas broad leaved crops often don't recover even after treatment.

Management and Control:

Baits are often used. They are not effective on young snails that are less than 7 mm diameter as they tend to eat decaying matter and don't consume the baits.

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

Monitor in summer for stubble management options; autumn for burning, cultivating and baiting; winter for re baiting and refuge treatment; and spring for grain contamination.

Avoid liming paddocks as this aids survival of the snails.

Graze or burn stubble to remove refuges.

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

If possible, burn in autumn to kill surface dwelling species.

Monitor paddocks for snails in autumn 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.

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.

Thresholds:

On open areas count the number of snails in 10 quadrats that are 32 x 32 cm to give the number of snails per square metre. Control is usually worthwhile if there are more than 5/m-2 in Oilseeds or Pulses, 20/m-2 in cereals or 80/m-2 in pastures 1317.

Related Species:

Similar Species:

White Italian Snail (Theba pisana) is very similar but tends to have less distinct banding and the umbilicus (the hole at the centre of the spiral shell) is partially obscured rather than the circular hole of the Vineyard Snail.

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.

Micic, Svetlana, Henry, Ken, and Horne, Paul. (2007) Identification and control of pest slugs and snails for broadacre crops in Western Australia. Bulletin 4713. Department of Agriculture and Food Western Australia. Perth, 2007.

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Acknowledgments:

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