This app estimates apple scab infection risk. You choose a place and date, and the uspest.org server looks up the weather data and runs the risk model. This app then shows you the risk index values classified into risk categories. You can use these categories to adjust management actions, such as intensity of scouting, fungicide selection and fungicide application intervals.
This app is a newer, streamlined interface for the existing model, which is also available through MyPest Page.
Apple scab (from Pacific Northwest Plant Disease Management Handbook).
Select the "Inputs" tab, search for weather stations near you, and choose one either from a list or a map. Be aware that some weather stations have poor quality or missing data. Our software estimates the quality of each station, but you may wish compare results for several nearby stations.
Optionally, you may choose a start date and a span (number) of days. If you leave the start date blank, the end of the output will be five days in the future, using forecast weather data, and the app will count back to a start date in the recent past. The weather forecast data is from the National Weather Service's "NDFD" forecasts.
Then, select "Graph" or "Table" to run the model. Your output will appear after 10-20 seconds depending on server load.
Apple scab infection can be predicted by measuring temperature and leaf wetness, assuming the presence of inoculative ascospores. This model (based on Mills 1944 and adapted by Len Coop) predicts risk of infection by accumulating degree-hours conducive to infection during periods of leaf wetness, which we estimate from temperature, dewpoint, and windspeed. The result (a number 0 – 350, with 195 being the threshold for infection) is classified into a risk class:
Like most plant disease risk models, this one assumes that inoculum is present locally and that you have not recently applied a protective fungicide.
Technical information about apple scab and this model is available on our disease risk model documentation page.
Disclaimer: The index is intended to inform your decisions about management actions, such as choice and timing of control measures and intensity of scouting. It should supplement, not replace, the other factors you consider in making these decisions. Use at your own risk.
Automated email delivery of the disease risk index outputs displayed in this app is available at no cost. An email subscription offers model results for this and several other plant disease models, for up to three weather stations, on a schedule that you select. To subscribe, you will need a uspest.org account.
Next, use one of these buttons to run the model and see the output in the form of your choice.