Diagnosing snails in crops

There are three snail species that damage broadacre crops in Western Australia . Snail damage to crops has increased over the past ten years. It is estimated that WA growers spend $3 million annually to control them in coastal and high rainfall areas.

White italian snail
Small pointed snail hiding in wheat head
Small pointed snails hiding in wheat head.
White Italian snails in lupin crop

Suggested thresholds for control

  Oilseeds Cereals Pulses
Small pointed snail 20 per square metre (/m2) 40/m2 N/A
Vineyard 5/m2 20/m2 5/m2
White Italian snail 5/m2 20/m2 5/m2

What to look for

    Plant

  • Shredded leaves with total defoliation in some cases.
  • Canola is most affected.

    Insect Adult

  • The small pointed snail has a conical shell with brown bands of varying width. It is usually less than 10mm in length or diameter. It occurs on all soil types in the high rainfall area.
  • The white Italian snail is up to 30mm across, white with broken brown bands.
  • The vineyard snail is up to 20mm across with almost continuous brown bands. This and the white italian snail prefer alkaline sandy soils.

What else could it be

Condition Similarities Differences
Diagnosing slugs in crops Leave clear slime trails in the morning. Slugs hide during the day.

Where did it come from?

Contaminated stubble
Contaminated stubble
  • These snails were introduced from Europe.
  • Movement of vehicles, materials and equipment are the main way that snails enter farms and spread between paddocks and farm rubbish dumps often have high snail numbers.
  • Stubble retention favours snail buildup.
  • Liming soil also favours snails by supplying calcium that they require for their shells.

Management strategies

Soil application
Soil application
Green bridge control
Green bridge control
  • Tillage will reduce snail numbers but baits are required for in-crop control. Early application of pellets is preferable while seedlings are small.
  • It is essential to spread pellets when snails are active after rain and to apply at recommended rates. Spring baiting is ineffective.
  • Baits alone may not provide sufficient control so it is necessary to carry out additional management practices.
  • Control of summer weeds (‘green-bridge’) results in fewer snails being present in crops and also increases the effectiveness of baits by removing food competition.
  • Weed control along fence lines, around dams and in remnant bush decreases breeding refuges for snails.
  • Burning stubble can reduce snail numbers by 90% however, soil type and risk of wind erosion needs to be taken into consideration.

Economic and financial considerations

To assist in assessing the economic risk and financial costs associated with various treatment strategies go to MyEconomicTool

There may be other economic and financial implications that need to be considered when choosing a management option. These may include:

Pre-crop
  • Understand the risk of snails being present and potential yield losses associated with snail feeding damage.
  • Assess the costs and benefits of taking preventative action such as removing a ‘green bridge’ or destroying stubble.
In-crop
  • Compare the costs, benefits and risk of each management option against doing nothing.
  • Consider risk and associated costs or savings of no treatment or delaying treatment.
  • Ignore all previous treatment costs in assessing current management options.
  • Undertake a ‘what if’ scenario analysis to see what impact changing variables (e.g. grain price and seasonal conditions) have on the economic outcome.
Post-crop
  • Consider using an integrated pest management system.

View these economic considerations in more detail.

How can it be monitored?

  • Snails are usually found near stumps, fencelines and under stubble.

Further information

Where to go for expert help

Page last updated: Monday, 1 May 2017 - 12:12pm