Pre-crop
Assess the risk of powdery mildew occurring.
- Are you in a high risks area? Are you sowing early? Are you sowing a susceptible variety?
Assess the costs and benefits of taking preventative action.
- Use whole farm budgeting to compare the costs, benefits and risk of alternative actions. If considering planting other crops or more resistant varieties, ensure you work out the opportunity cost of possible lower yields from selecting resistant varieties or lower gross margins from an alternative crop. The expected cost of seed treatment and follow up sprays for each variety or crop need also to be compared.
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 as well as the risk that the efficacy of fungicide applied later in the season may be lower.
- When comparing treatment options allow for different efficacies, fungicide resistance, need for further treatment, different application methods, timing of treatment, seasonal conditions and opportunities to control other diseases.
Ignore all previous treatment costs in assessing current management options.
- Costs associated with previous treatments should be ignored as they are ‘sunk costs’ and will have no bearing 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 cost of treatment then the economic outcome will still be better than doing nothing about it.
Post-crop
Use integrated disease management to reduce disease pressure and reliance on fungicides.
- Due to rising resistance to fungicides consider other farm management strategies to control future outbreaks of powdery mildew such as choosing a resistant variety, avoiding sowing back into affected barley stubble, destroying green bridges, increasing potassium and, to reduce the canopy, review nitrogen rates and graze crops.
To assist in assessing the economic risk and financial costs associated with various treatment strategies go to MyEconomicTool