Adult - The shell is usually less than 20 mm in diameter.
Colour - The shell is mainly white but often has fine brown concentric lines. The body is creamy white.
Body - Creamy white, soft and slimy body enclosed within a hard spiral shell.
Umbilicus - Partially obscured 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 and are often found on green summer weeds. 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:
Alkaline, sandy soils that usually have free limestone in the profile.
Origin and History:
Distribution:
Widespread.
In WA, they tend too occur close to the coast because this is where the limestone soils occur.
Significance:
Snails don't feed on Canola or cereal seed but will attack all plants soon after germination. 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.
Beneficial:
Detrimental:
Pest of cereal crops, pastures, grapevines and ornamentals.
Contaminate pasture with their slime making it less palatable to stock.
They climb cereal plants and are harvested with the grain, increasing its moisture content and contaminating it with the decaying snail remains.
They may contaminate dried vineyard fruit products.
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.
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.
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, 20/m-2 in Pulses, 5/m-2 in cereals or 80-2 in pastures 1218.
Related Species:
Similar Species:
Vineyard Snail (Cernuella virgata) is very similar but tends to have more distinct banding and the umbilicus appears as a circular hole that is not partially obscured as it is White Italian 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 for more information.