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 three categories based on the Fire blight situation in the orchard last year and this year as follows:

Apples

  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 three 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.

Summary of the Actual Fire Blight Risk during Apple Bloom Period 2017

Actual (not predicted) weather data has been entered into the Cougar Blight Model from April 19 - June 11, 2017 to determine the actual conditions for Fire blight infection of open blossoms during apple bloom period across the apple growing regions of Ontario. The periods for risk of fire blight infection was different for most Ontario apple growing regions except for the period May 16- 21 when the risk was 'High' or 'Extreme/Exceptional' in most regions of the province.

The risk was 'High' or 'Extreme/Exceptional' in many regions of Southwestern Ontario including Essex, Elgin, Kent, Middlesex, Lambton and Oxford counties during April 27 -30 when some early varieties in southwest were coming into bloom and again on May 17 - 21 at the end of bloom period for some late varieties. The risk was also 'High' or 'Extreme/Exceptional' in many regions of Southwestern Ontario for several days during May 29 - June 11 when trees had open secondary 'rat tail' blossoms.

The risk was 'High' or 'Extreme/Exceptional' in the Norfolk, Haldiman, Hamilton, Wentworth and Brant during May 17-21 when apple were coming into bloom and for several days during May 29 - June 9. The risk was also 'High' or 'Extreme/Exceptional' from June 9-11 when trees had many secondary or 'rat tail' blossoms.

The risk was 'High' or 'Extreme/Exceptional' in the Georgian Bay Regions during May 17-21 when apple trees were coming into bloom, for several days during May 29 - June 1 when many varieties were in bloom and during June 9-11 when trees were finishing bloom or had many secondary 'rat tail' blossoms.

The risk was 'High' or 'Extreme/Exceptional' in regions along Lake Huron including Grand Bend, Huron West, Bruce West and Grey West during May 17-21 when apple trees were coming into bloom and for several days during June 10-11 when trees had many secondary or 'rat tail' blossoms.

The risk was 'High' or 'Extreme/Exceptional' in Wellington and Waterloo regions during May 17-21 when apple trees were coming into bloom and during June 10-11 when trees had many secondary or 'rat tail' blossoms. During the period of May 29 - June 9 there were several days when the risk was 'Caution' or 'High'.

The risk was 'High' or 'Extreme/Exceptional' in the Niagara region during May 17-21 when many varieties were in bloom, during May 29 - June 1 and June 10-11 when trees had many secondary or 'rat tail' blossoms.

The risk was 'High' or 'Extreme/Exceptional' in the Peel, York and Halton regions during May 17-21 when many varieties were in bloom. The risk was 'Caution' or 'High' for several days during May 30 - June 4 and June 10-11 when trees had many secondary or 'rat tail' blossoms.

The risk was 'High' or 'Extreme/Exceptional' in Eastern Ontario including the Durham region during May 17-21 when most trees were in late pink to early bloom and June 7-11 when trees had many secondary or 'rat tail' blossoms. There were also several days when the risk was 'Caution' or 'High' during May 24 - June 1 when many trees were in full bloom.

Apples

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

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Apples - Fire blight occurred in the neighbourhood last year

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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
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 24 February 2017
Last Reviewed: 22 June 2017