Pointed Snails

Prietocella acuta - Pointed Snail

Prietocella barbara - Small Pointed 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 - The shell of the Small Pointed Snail is usually less than 10 mm long and that of the Pointed Snail is usually 12-18 mm long and the cone is sharper.

Colour - Greyish brown with brown bands of varying widths.

Body - Dark, soft and slimy body enclosed within a hard conical shell.

Wings - None.

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. Over summer they aestivate in debris, crops, up to 50 mm under the soil, under stumps or stones or they climb vegetation or posts to avoid high temperatures. 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:

They are not restricted to alkaline soils.

Origin and History:

Distribution:

Widespread.

Significance:

Small Pointed Snails are usually more prolific than the Pointed Snail.

Beneficial:

Detrimental:

Pest of pastures, crops and ornamentals.

Occasionally they can cause serious damage to young vines.

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 height 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.

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.

Cultivation to 5 cm deep to bury Pointed Snails will reduce populations by 40-60%.

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.

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 20/m-2 in Oilseeds, 40/m-2 in cereals or 100/m-2 in pastures 1317.

Biological Control:

A parasitic fly (Sarcophaga penicillata) has been introduced to help control the Pointed Snail (Prietocella acuta)

Related Species:

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.