Cutworm - economic considerations for management

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

Pre-crop

Understand the potential yield losses associated with cutworm feeding damage.

  • Caterpillars feed at or near ground level on the leaves or stem, with large caterpillars often cutting off the stems and killing young seedlings. 

Assess the costs and benefits of taking preventative action.

  • The cost of preventing cutworms should be weighed against the savings of non-action in the event that there is no major infestation during the year. Costs include the opportunity cost of the cost of spray and biological costs such as also killing natural enemies of cutworms. Biological control agents can be important in some years.

Assess the cost and benefits of controlling summer weeds (green bridge) to reduce feed source.

  • Early and complete control of any green bridge two weeks before planting will minimise survival of cutworm larvae.

In-crop

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

  • 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.
  • Compare the costs ensuring you allow for the possibility of further treatment.
  • Selection of insecticide may be influenced by the opportunities to control other insects.
  • If applying insecticide at the same time you would with other treatments only assess the marginal cost of application, i.e. the cost of going over the paddock is not included as it would have been incurred anyway. The marginal cost is the cost of the insecticide and any additional time needed to prepare and apply.
  • Consider choosing a treatment option where the expected return is sufficient to offset its 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.

Ignore all previous treatment costs in assessing current management options.

  • Costs associated with previous treatments should be ignored as they cannot be recovered. They are ‘sunk costs’, i.e. even if the current treatment results in the crop not breaking even, provided the additional benefit of the treatment is greater than the cost of treatment, then the net return from treatment is still 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 net income.

  • 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.

Post-crop

Consider using an integrated pest management system and include a resistance management strategy into your spray program.

  • Include a resistance management strategy into your spray program to reduce the chance of cutworms and other non-target pests becoming resistant. If monitoring indicates the need to spray, then insecticide choice (such as ‘soft’ on natural enemy chemicals) and rotation of chemical groups needs to be considered, along with appropriate spray application.

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 - 12:19pm