Disease forecasting (Apple canker)

The ADEM system is a PC-based system and contains a disease forecasting model for Neonectria canker and fruit rot. The disease models are driven by the following weather variables recorded on a logger and downloaded to a PC:

• Rainfall
• Surface wetness duration
• Ambient temperature
• Ambient relative humidity

The models use the weather data to determine the favourability of the weather for Neonectria infection of fresh leaf scars and near-mature fruits and indicate the incidence of disease likely to occur at these two infection sites.

Forecast of cankers

The model assumes that the inoculum level is high and varietal susceptibility to Neonectria is high.

• In addition to weather, the system requires inputs on the age of leaf scars based on inputs on date for leaf fall – 10%, 50%. 90% leaf fall.
• Currently the model for leaf scar infection is not used in practice since it records infection that has already occurred and as there are no fungicides with eradicant action against N. ditissima and so it is difficult to make use of the information.

Forecast of fruit rot

The model will be revised to include new data on fruit susceptibility to Neonectria rot from recent inoculation experiments.