Slugs - economic considerations for management

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


Understand the risk of slugs being present and potential crop losses associated with slug feeding damage.

  • Slugs are usually found on heavy soils and wet areas in the high rainfall area. Slugs survive over the summer under stubble, under rocks, in cracks in the ground.
  • Attacks on emerging crops can cause major economic losses, even when slug numbers are relatively low. Slugs will eat all parts of a crop plant, however, seedlings are the most vulnerable and this is the time when major economic losses can occur.

Assess the costs and benefits of taking preventative action such as removing any ‘green bridge’ or destroying stubble.

  • Depending on the slug species control of summer weeds (green-bridge) may increase the effectiveness of baits by removing food competition.
  • Burning and tillage can reduce reticulated slugs but black keeled slugs are relatively unaffected.

If seeding susceptible crops, consider costs and benefits of increasing seeding rates.

  • If planting a susceptible crop, increase seeding rates in paddocks where slugs have been present and follow good agronomic practices to get the crop established.


Compare the costs, benefits and risks of each management option against doing nothing.

  • What are the likely outcomes of each management option? When the result of treatment is unknown consider the most likely (expected), as well as the worst and best results from each treatment option.
  • When calculating the cost of non-treatment, assess the potential risk of yield losses.
  • Consider biological control of predatory insects and organisms, such as carabid beetles and nematodes, which play a role in limiting slug populations.
  • Compare the costs ensuring you allow for the possibility of further treatment.
  • Selection of pellets may be influenced by the opportunities to control other pests.
  • Best practice is to bait without applying any other treatments, therefore the cost of going over the needs to be included as well as the cost of the pellets and any additional time needed to prepare and spread.
  • Consider choosing a treatment option where the expected return is sufficient to offset risk of the treatment. We all have different attitudes to risk when making decisions. The probability (risk) of outcomes can be affected in terms of responsiveness (efficacy), application rates, products, application methods and climatic conditions. The economic calculator can assist with this decision.

Consider risk and associated costs or savings of no treatment or delaying treatment.

  • To avoid unnecessary costs of spreading of pellets or baits regularly monitor slug numbers.
  • It is essential to spread pellets when slugs are active after rain and to apply at label rates. Check pellet distribution after application and re apply if no baits can be found as this usually indicates a high density that has eaten all the bait. 

Ignore all previous treatment costs in assessing current management options.

  • Costs associated with previous treatments should be ignored. They are ‘sunk costs’ and will not have any effect on the economic outcome of a decision that is taken at this stage of the crop cycle, i.e. even if the current treatment results in the crop not breaking even, provided the additional benefit of the treatment exceeds the additional cost, then the economic outcome will still be better than doing nothing about it.

Undertake a ‘what if’ scenario analysis to see what impact changing variables (e.g. grain price and seasonal conditions) have on the projected economic outcomes.

  • Some variables can influence decision outcomes but are not directly controllable, including fluctuations in wheat price, the value of the Australian dollar and seasonal influences. But they need to be considered, even if we cannot include them directly. A ‘what if’ analysis may help you in your decision making.


Consider using integrated pest management system – consider costs and benefits of removal of stubble and green bridges, other pests and diseases and biological impacts.

  • As no single control method will provide complete protection, an integrated approach is needed.

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

Where to go for expert help

Tamara Stretch
+61 (0)8 9881 0225
Page last updated: Tuesday, 2 September 2014 - 12:35pm