Snails

Cernuella virgata - Vineyard Snail

Prietocella acuta - Pointed Snail

Prietocella barbara - Small Pointed Snail

Helix aperta - Green Snail

Helix aspersa - Common Garden Snail

Theba pisana - White Italian Snail

Family: Helicidae

Order: Eupulmonata

Class: - Gastropoda


Synonyms:

Pointed Snail Prietocella acuta was Cochlicella acuta

Small Pointed Snail Prietocella barbara was Cochlicella barbara

Description:

Adult -

Colour -

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

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:

They seek shelter under plants or debris during the day. 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 laying eggs commences soon after mating. Egg clusters are laid in the top soil from autumn to spring. Eggs hatch about 2 weeks after they are laid. The juveniles feed in winter and spring and aestivate over summer to become sexually mature at one year old.

Habitats:

Origin and History:

All pest species are introduced.

Distribution:

Widespread.

Significance:

Major pests of crops, pastures, vegetables 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.

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.

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. Look for them on moist, warm still nights or search for silver slime (mucous) tracks in the morning.

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.

Baits are not effective on young snails as they tend to feed on decaying matter and don't eat the baits.

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 the numbers exceed those below for various crops.


SpeciesOilseedsCerealsPulsesPastures
Small Pointed Snail2040N/A100
Vineyard Snail520580
White Italian Snail520580
Adapted from Micic et al (2007)

Related Species:

Slugs.

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.

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.