Pre-crop
Assess the risk of septoria tritici occurring.
- Is your area susceptible to septoria tritici this year? Consider paddock history (particularly wheat on wheat in stubble retention farming systems), recent outbreaks in the district and projected climatic conditions. If so, consider planting other crops or less susceptible varieties or reduce surface wheat stubble before seeding wheat after wheat. Use whole farm budgeting to compare the costs, benefits and risk of alternative actions.
Understand the potential yield losses associated with infection.
- Potential yield loss is dependent on climatic conditions (moisture and temperature) and the resistance rating of the variety. Because the majority of varieties currently grown in Australia have partial resistance to septoria tritici blotch, losses from this disease are now insignificant. However, if susceptible and very susceptible varieties are grown, this disease is likely to cause annual average losses of up to 20% with individual crop losses much higher.
Assess the costs and benefits of taking preventative action.
- The cost of preventing septoria tritici should be weighed against the savings of non-action in the event of disease occurring. Costs include the opportunity cost of lower yields from selecting resistant varieties, lower gross margins from an alternative crop, or the cost of seed treatment. For example, if septoria tritici does not occur how much better off would you have been if you had not taken unnecessary steps to prevent it.
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.
- When calculating the cost of non-treatment, assess the potential risk of yield losses and quality downgrades. This will depend on disease resistance of the variety and how early the disease starts or is detected in the crop. Quality reductions such as lower hectolitre weights can also reduce revenue.
- Compare the costs ensuring you allow for the possibility of further treatment.
- Selection of fungicide may be influenced by the opportunities to control other diseases or weeds.
- Consider costs and benefits for both ground and aerial application methods.
- 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.
Consider risk and associated costs or savings of delaying treatment.
- Applying fungicide as soon as possible after the first detection of septoria tritici is usually the most effective fungicide control.
- However, there may even be economic benefits from delaying treatment and monitoring the progress for a period, particularly for adult plant resistance varieties. The season may change and septoria tritici may not cause as much damage as initially expected.
- Alternatively, if no action is taken and the disease infestation spreads the treatment cost and yield losses could be higher.
- Spraying after crop flowering finishes is generally not economic but further research is being done on this.
Consider the potential risk of re-infection and costs of further treatment.
- The length of time a fungicide is effective depends on the active ingredient, rate of application, and climatic conditions. The probability of follow up treatment is dependent on the variety, time to harvest, and upcoming climatic conditions.
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 costs.
- 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 longer term consequences of not adequately treating septoria tritici.
- When making your decision, look beyond in-crop benefits and costs to also consider possible future effects, i.e. future costs and benefits. Saving money in the short term by not treating today may result in adverse future consequences. For example a build-up or spread of septoria tritici, or possibly a breakdown in cultivar resistance could have serious longer term consequences. This economic calculator does not consider these post-crop implications.
- To reduce the cost and risk of another outbreak in next season’s crop, consider destroying stubble by grazing or cultivation (if erosion is not a problem). Such practices will have more effect if undertaken on a district basis. If not possible, consider growing an alternative crop or resistant variety the following year.
To assist in assessing the economic risk and financial costs associated with various treatment strategies go to MyEconomicTool