Lucerne flea - economic considerations

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


Understand the potential yield losses associated with lucerne flea feeding damage.

  • Lucerne flea can kill seedling crops and pastures and re-growth of lucerne.
  • Yield loss varies with the growth stage of the plant.

Assess the cost and benefits of taking preventative action.

  • Assess the costs and potential benefits of all preventative actions such as destroying any green bridge with chemical, cultivation or heavy grazing prior to sowing, a bare-earth spray immediately after seeding and/or insecticide-treated seed.

Assess the cost and benefits of controlling summer weeds to reduce potential feed sources for fleas.  


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.
  • Insecticides often provide the most effective means of control.
  • Compare the costs of action ensuring you allow for the possibility of further treatment. A follow up spray is often recommended to control later hatchings.
  • An option is to use a bare-earth pre-emergent insecticide followed by a foliar spray soon after emergence.  
  • Timely spot or local spraying can be effective in preventing population build-up and spread.
  • Selection of insecticide may be influenced by the opportunities to control other insects.
  • When calculating the cost of not undertaking a treatment option, assess the potential risk of yield losses and quality downgrades. This will depend on size of the flea population and how early the infestation starts or is detected in the crop.
  • If applying insecticide at the same time you would with other treatments only assess the specific chemical cost of the application, i.e. the cost of going over the paddock is not included as it would have been incurred anyway. The additional (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 the 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 spraying, monitor lucerne flea damage and numbers.  
  • Alternatively, if no action is taken and the lucerne flea population multiplies the treatment cost and yield losses could be higher.

Ignore all previous treatment costs in assessing current management options.

  • Costs associated with previous treatments are ‘sunk costs’ and should be ignored as they will not affect the economic outcome for a treatment decision taken now, 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, the economic return will still be higher than doing nothing about it.


Continue to monitor.

  • Monitoring is the key to reducing the impact of lucerne flea. A planned out program of timely spring and autumn sprays with effective chemicals over two to three years can reduce populations to very low levels.
  • In pasture the best results are usually about seven days after the paddock has been cut for hay or heavily grazed.  

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 - 12:24pm