Weather, models & degree days

Fire Blight Risk Assessment

This program presents assessments of the risk of Erwinia amylovora infection of apples and pears, based on two models and using calculations based on weather data stored in the UC IPM weather database.

The degree-hour fire blight model assesses actual conditions for Erwinia amylovora bacterial growth and infection. It also indicates when treatment is unnecessary. It takes into account early bloom and periods of continuous cool weather, allowing adjustments in treatment timings.

The mean air temperature model predicts colonization of blossoms by the bacterium, based on daily air temperatures.

Use the models in conjunction with weather data gathered and stored in the UC IPM weather database. If possible, start the season with a full soil water profile so you can avoid irrigation during bloom, which affects the local relative humidity.

Spray Considerations

Model results suggest when you will need to treat for fire blight. For complete information, see the UC IPM Pest Management Guideline for Fire Blight on Pear.

Model Setup

Select a weather station (Grouped by county)

Start Date
End Date