Adult - The shell is rarely more than 25 mm diameter.
Colour - Immature snails have a yellow green shell and a cream body. Adults have a green to dark brown shell of uniform colour.
Body - Soft and slimy body enclosed within a hard spiral 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:
In spring they burrow 25-150 mm underground and aestivate over summer to emerge in autumn after rain and lower temperatures.
Habitats:
Occur in a wide range of soil and vegetation types, including natural bushland.
Tend to live on the ground and prefer open grasslands.
Origin and History:
Mediterranean.
Recently introduced to WA.
Distribution:
Established in the Perth metropolitan area.
Significance:
Beneficial:
Detrimental:
They can damage a wide range of plants including most vegetables, cereals, grasses, lupins and some native plants.
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.
Legislation:
In WA, outside of the Perth metropolitan area, they are declared and efforts to eradicate should be encouraged.
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:
Common Garden Snail (Helix aspersa) are larger and have a banded or mottled brown shell.
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
1217
Acknowledgments:
Collated by HerbiGuide. Phone 08 98444064 for more information.