Fire Blight Alert and Risk Map Overview

Risk for fire blight infection can be high as temperatures become warm and wet weather occurs during bloom.  Growers can assess risk by using the Fire Blight Disease Prediction Model and selecting specific county and orchard history. This model incorporates the previous 4 days of weather data plus adds a 7-day forecast for estimating leaf wetness and temperature (thereby estimating risk for bacterial growth and infection). There are 66 Mesonet weather stations throughout Kentucky, and weather information for the model is based on data from the closest weather station. For a mobile (phone or tablet) friendly version of this site, visit http://weather.uky.edu/dim.html.

Figure 1: An example of a prediction model query for Fayette County on April 11, 2016. The blue arrow indicates the current date (date model was searched). Risk is based on weather from the previous 4 days. Note that conditions on April 11 were warm and wet, which are favorable for the fire blight pathogen. However, the previous days were cool and dry, which reduced overall risk for infection. The red arrow, on the other hand, indicates forecasted risk for a future date. It is based on temperature and moisture (in this case, humidity) forecasts for the 4 previous days.

Figure 1: An example of a prediction model query for Fayette County on April 11, 2016. The blue arrow indicates the current date (date model was searched). Risk is based on weather from the previous 4 days. Note that conditions on April 11 were warm and wet, which are favorable for the fire blight pathogen. However, the previous days were cool and dry, which reduced overall risk for infection. The red arrow, on the other hand, indicates forecasted risk for a future date. It is based on temperature and moisture (in this case, humidity) forecasts for the 4 previous days.

Remember that apple and pear trees must be in bloom for predictions to be accurate. The example above indicates fire blight risk for a single county on a single date.  Growers are encouraged to regularly check risks for their particular county in order to obtain the most accurate analyses and county-specific forecasts.  Infection by the fire blight bacterium occurs during bloom, thus, protectant antibiotics should be applied when risk is high and trees are in bloom.

Apple development stage varies across the state. Early apple varieties in western Kentucky are at petal fall. In northern and central Kentucky, apples are between pink and 40% bloom, and in eastern KY, apples are between pink and 10% bloom. Most Asian pears are beyond risk for blossom blight, but European pears are in full bloom in cooler regions of the state.

Resources

Information regarding prevention and management of fire blight can be found in:

  • Commercial Fruit Pest Management Guide (ID-232)
  • Backyard Apple Disease Management Using Cultural Practices (PPFS-FR-T-21)
  • Fire blight (PPFS-FR-T-12)
  • Fire blight of Apple (Video)

 

By Nicole Ward Gauthier, Extension Plant Pathologist and Kimberly Leonberger, Extension Associate

 

Posted in Fruit