Apple canker (Neonectria ditissima) model

During the growing season, the presence of wounds is limited, and other fungicide applications often control potential infections. The critical period is in autumn: picking wounds, leaf fall wounds, and pruning wounds are all entry points for the fungus at a time when climatic conditions are favourable to infections and when healing is slow.

The time between infection and visual symptoms varies from 5 days to over a year. The length of the incubation period depends on the variety, amount of inoculum, temperature, and time of year. At high temperatures, symptoms sometimes do not even appear. There is currently too little known about the process, and therefore, the onset of symptoms is not included in the model.

The Model

In the bar below the graph, dark blue represents the periods when your weather station recorded rain. Light blue is the period when there is wetness on the leaves; this is calculated based on your records of rainfall, relative humidity, and leaf wetness.

The middle graph indicates the periods of spore ejection (in yellow), germination (in white) and infection (red line). During each rain event, the number of conidia deposited on the wound surface increases with the amount of rainfall. Ascospores discharge is simulated at a constant rate as long as the temperature is over 5 C. Spore germination is dependent on temperature.

The top graph allows visualisation of wound healing as a function of temperature. The user can define the start date of leaf fall (5% of fallen leaves) in the BIOFIX tab and see when there are still sensitive wounds. For the moment, the model does not take the number of injuries into account for the risk calculation. Leaf fall is only shown and modelled as a normal statistical distribution to cover all varieties and situations.

Potential infection events are calculated throughout the year based on weather data. As the presence or absence of sensitive wounds in the orchard is not taken into account in RIMpro, infection events should however only be considered if there are recent wounds on the tree.

Treatments

Users who have an individual RIMpro account can enter fungicide applications in their orchards. The degradation of the fungicidal cover by precipitation is represented by a grey layer over the infection events.