Pre-crop
Understand the potential yield losses associated with rutherglen bug (RGB) feeding damage.
- In canola crops, if there is a warm start to the season, RGB in high population densities can cause death in moisture stressed seedling crops. RGB present in spring are not known to cause yield loss in canola crops, though they can be a grain contaminant.
Assess the cost and benefits of taking preventative action.
- Assess the costs and potential benefits of all preventative actions such as managing weeds in and around paddocks prior to sowing can reduce the likelihood of RGB moving from dying weeds onto emerging seedlings.
In-crop
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.
- Cool weather, for example, several days of continuous rain decreases RGB populations.
- Insecticide spray is usually economic if seedlings are withered and rain is not expected.
- When calculating the cost of non-treatment, assess the potential risk of seedling losses.
- High numbers of RGB in spring can be harvested with the grain. Aerial spraying to suppress RGB numbers is not usually considered economic when compared to costs of cleaning grain.
- 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 as other treatments only assess the actual cost of the chemical application, that is, 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.
- Several days of continuous rain usually stops an epidemic.
- Alternatively, if no action is taken and warm weather continues, population of RGB will multiply and the treatment cost and yield losses could be higher.
Consider further costs associated with re-infestation.
- Repeated influxes of migrating adults can make repeat applications necessary.
Ignore all previous treatment costs in assessing current management options.
- Costs associated with previous treatments should be ignored. They are ‘sunk costs’ and have no bearing on the economic outcome for a decision now, that is, even if the current treatment results in the crop not breaking even, provided the additional benefit of the treatment exceeds the cost, then the economic outcome will still be better than doing nothing about it.
Post-crop
Include a resistance management strategy into your spray program to reduce the chance of RGB and other non-target pests becoming resistant.
- An integrated approach to pest management where paddock selection and weed free fallow periods are used.
To assist in assessing the economic risk and financial costs associated with various treatment strategies go to MyEconomicTool