Fire Blight Prediction Pears
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:
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.
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 Pear Bloom Period 2018
Actual (not predicted) weather data has been entered into the Cougar Blight Model from May 1 - June 6, 2018 to determine the actual conditions for Fire blight infection of open blossoms during pear bloom period across the pear growing regions of Ontario in 2018 (see maps below). Despite the cold weather experienced in April, pear trees developed very quickly during the early part of May 2018.
Pear trees were at late pink to early bloom in the Essex, Elgin, Kent, Niagara and Norfolk region on May 14, king bloom to full bloom on May 18 which lasted until petal fall around May 23-28. Early bloom occurred around May 16 in the Lambton, Kent and Middlesex regions followed by king bloom around May 18, full bloom on May 23 until petal fall around May 28. Early bloom began around May 18 with full bloom around May 25 in the Georgian Bay and Eastern Ontario pear growing regions an lasted until petal fall around May 28 -30. During this period, the risk of blossom infection in the Essex region was 'High' to 'Extreme/Exceptional' in orchards with active fire blight cankers and 'Low' to 'Caution' in orchards where fire blight was in the neighbourhood the previous year on May 14 in most pear growing regions except in the Essex, Kent, Niagara, western Georgian Bay and far eastern regions of the province. The risk reduced to 'Caution' and 'Low' on May 15 except for the far eastern regions of the province where the risk remained 'High' in orchards with active fire blight cankers. The risk became 'High' to Extreme/Exceptional' in most pear growing regions except in areas close to the open water of the Great Lakes from May 17 - 22 for orchards with active fire blight cankers but remained 'Caution' in the Essex, Kent and Niagara regions for orchards where fire blight was in the neighbourhood the previous year from May 17- 19. The risk became 'High' to 'Extreme/Exceptional' for most pear growing regions starting around May 24 in both orchards that had active cankers or orchards where fire blight was in the neighbourhood but not necessarily in the orchard the previous year. This 'High' to 'Extreme/Exceptional' risk event lasted beyond petal fall in these pear growing regions into early June. Unfortunately secondary or 'rat tail' bloom was present in many orchards after petal fall which are vulnerable to fire blight infection.
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.
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