Fire Blight Prediction Apples

Below is the seven day predicted Fire blight risk maps based on the Cougarblight model.

To use the maps below, orchards must be assigned to one of two categories based on the fire blight situation in the orchard last year and this year as follows:


  1. Fire blight occurred in the orchard last year and is now active in your neighbourhood
  2. Fire blight occurred in the neighbourhood last year

Once the orchard has been assigned to one of the categories above, locate the region the orchard is in and follow the animated maps for the predicted fire blight risk corresponding to the date at the top of the map.

Map Legend

The following risks are colour coded and designated as follows:

Low: Indicates a low risk of fire blight occurring. Wetting of blossoms during these temperature conditions has not resulted in new infections in past years. The blossoms within a few meters of an active canker may be an exception.

Caution: Wetting of flowers under these temperature conditions is not likely to lead to infection, but the possibility increases if the weather becomes warmer and wetter. Weather forecasts should be carefully monitored. If antibiotic materials are not being used, blossom protection with other materials should be initiated one or two days prior to entering a high infection risk period. Continue appropriate protective sprays until the infection risk drops below the "high" threshold.

High: Under these temperature conditions, serious outbreaks of fire blight have occurred. Orchards that recently had blight are especially vulnerable. The risk of severe damage from infection increases during the later days of the primary bloom period, and during petal fall, while blossoms are plentiful. Infection is common, but more scattered when late blossoms are wetted during high risk periods. The potential severity of infection increases if a series of high risk days occur.

Extreme/Exceptional: Some of the most damaging fire blight epidemics have occurred under these optimum temperature conditions, followed by blossom wetting. These infections often lead to severe orchard damage, especially during primary bloom or when numerous secondary blossoms are present. As the season progresses, secondary blossoms tend to form less frequently, and hot summer temperatures of 35°C and above greatly reduce the frequency of new blossom infections.

Current growth stages for key apple growing regions

County/Region Growth Stage Blossom blight risk?
Essex - Chatham-Kent Developing fruit No
Middlesex - Elgin Developing fruit No
Norfolk Developing fruit No
Niagara Developing fruit No
Grey Developing fruit No
Durham developing fruit No
Quinte developing fruit No


Apples - Fire blight occurred in the orchard last year and is now active in your neighbourhood

Text equivalent

Apples - Fire blight occurred in the neighbourhood last year

Text equivalent

Model Information and Cautions

As with any model, the risk is a general guide and environmental conditions may be more conducive for fire blight infection in your orchard than what is indicated by the maps. All growers are encouraged to run either the Cougarblight or Maryblyte model with data generated in their orchard for a more accurate prediction.

A risk has been calculated for each date in each region based on the weather prediction and assumes that open blossoms are present and dew or rain will wet the blossom which is necessary for a fire blight infection to occur. If there are no open blossoms or if wetting of the open blossoms does not occurs, infection will not take place. However, it only takes a little dew to wash the fire blight bacteria into the open blossom for infection to occur.

For more information:
Toll Free: 1-877-424-1300
Author: OMAFRA Staff
Creation Date: 24 February 2017
Last Reviewed: 14 June 2019