BEAN DOWNY MILDEW RISK FORECAST SCHEME
How does the forecast scheme work?
In general the disease is favoured by cool and wet conditions. Using weather data collected by automatic logging equipment, rainfall over the preceding six days and temperature over the preceding three days are compared to long term averages expected at the monitoring locations. In this way, short term episodes of favourable conditions will not overshadow a season which has largely been unfavourable for pathogen infection - or vice versa.
A numerical risk factor for the temperature and rainfall is combined and categorised into three levels of infection risk based on when the disease has appeared in monitored fields in recent seasons. When the infection risk is described as 'Moderate' or 'High', infection will be expected if the pathogen is present. Unfortunately, real-time detection of pathogen presence in the air around crops is not currently feasible without hugely expensive equipment. For this reason the forecast scheme makes the assumption that inoculum is always present and capable of infecting susceptible plants.
The scheme provides warnings of conditions that favour downy mildew in crops which are not exposed to the soil borne stage of the pathogen's life cycle. The fungus produces resting spores that can survive in the soil for upto eight years, therefore crops growing where peas and/or beans have suffered mildew attacks in recent seasons may become infected as they emerge from the soil.
A final point to consider is that the weather recording stations are only representative of limited areas around their locations. Rainfall in particular can vary in amount across short distances, so fields not too far away may experience more or less than the recorded precipitation. CropMonitor is working to try to expand the available network of weather stations able to make observations useful for agricultural applications but for the time being we are restricted in the numbers and placement of our equipment.
In general the disease is favoured by cool and wet conditions. Using weather data collected by automatic logging equipment, rainfall over the preceding six days and temperature over the preceding three days are compared to long term averages expected at the monitoring locations. In this way, short term episodes of favourable conditions will not overshadow a season which has largely been unfavourable for pathogen infection - or vice versa.
A numerical risk factor for the temperature and rainfall is combined and categorised into three levels of infection risk based on when the disease has appeared in monitored fields in recent seasons. When the infection risk is described as 'Moderate' or 'High', infection will be expected if the pathogen is present. Unfortunately, real-time detection of pathogen presence in the air around crops is not currently feasible without hugely expensive equipment. For this reason the forecast scheme makes the assumption that inoculum is always present and capable of infecting susceptible plants.
The scheme provides warnings of conditions that favour downy mildew in crops which are not exposed to the soil borne stage of the pathogen's life cycle. The fungus produces resting spores that can survive in the soil for upto eight years, therefore crops growing where peas and/or beans have suffered mildew attacks in recent seasons may become infected as they emerge from the soil.
A final point to consider is that the weather recording stations are only representative of limited areas around their locations. Rainfall in particular can vary in amount across short distances, so fields not too far away may experience more or less than the recorded precipitation. CropMonitor is working to try to expand the available network of weather stations able to make observations useful for agricultural applications but for the time being we are restricted in the numbers and placement of our equipment.
