Fireblight infection conditions - Cougarblight model

Background Information for this page
Return to radar list for Middletown RI
Weather data for Middletown RI.  Forecast values begin September 20, 2011
     This table shows estimates of RELATIVE daily fireblight blossom infection risk based on weather conditions.  Rating criteria are from the Cougarblight 2010 model developed in Washington and Oregon by Dr. Timothy J. Smith.     
      ABSOLUTE risk depends on the amount of fire blight bacteria in the area, the number of open flowers, and cultivar and rootstock susceptibility.  Relative infection risk may be overstated for first few days of bloom because fire blight bacteria may not have been distributed to open flowers.   
      Gray shading indicates dates when most trees will have lost open blossoms, and are therefore no longer susceptible to blossom infection.  These dates included for later blooming cultivars and for late-blooming young trees.  Absolute risk is much lower on these dates than during full bloom, but apple trees with open blossoms on these dates are susceptible to the risk rating shown.  
      Fireblight infection can occur without rain if there is "heavy" dew.  But heavy dew is not defined in weather reports.  As a rough guess, if there is no rain on a day, but leaves are expected to be wet for at least 3 hours, then infection risk is reported with "if dew" attached.  Infection potential may be overstated on days when the "if dew" tag is attached.
     Fire blight risk categories vary by block history:
   I  = No active fire blight within 1 mile of the orchard this year or last year.  Requires 500 – 800 heat units for HIGH rating, 801 – 1000 for EXTREME!, and 1001+ for EXCEPTIONAL!
  
II = Fire blight was present within 1 mile of the orchard last year, but not currently active in the area this year.
Requires 200 – 350 heat units for HIGH rating, 351 – 500 for EXTREME!, and 501+ for EXCEPTIONAL!

  
III = Active fire blight cankers within 1 mile of the orchard this year. 
Requires 100 – 200 heat units for HIGH rating, 200 – 300 for EXTREME!, and 301+ for EXCEPTIONAL!
 If blossom infection occurred May 25, then blossom blight would be noticeable by June 6, and shoot blight by June 16.
Range of potential open blossom dates
for McIntosh and similar cultivars
Cougarblight Heat Units,
Inches Rain, & 
Leaf Wet Hours
I - No FB within
one mile last year
or this year
II - FB within one mile last year, but not active within one mile this year III - FB active within one mile of orchard this year.
Mac King Bloom
 Tue, May 10 
2 HU,  0.03'',  7 hrs Low Low Caution
Wed, May 11  6 HU,  0.01'',  15 hrs Low Low Caution
Thu, May 12  10 HU,  0.0'',  0 hrs Low Low Low
Fri, May 13  15 HU,  0.0'',  1 hrs Low Low Low
Sat, May 14  14 HU,  0.14'',  24 hrs Low Low Caution
Sun, May 15  18 HU,  0.52'',  24 hrs Low Low Caution
Mon, May 16  15 HU,  0.33'',  24 hrs Low Low Caution
Tue, May 17  13 HU,  1.40'',  24 hrs Low Low Caution
Wed, May 18  28 HU,  0.29'',  24 hrs Low Low Caution
Thu, May 19  39 HU,  1.04'',  24 hrs Low Low Caution
Fri, May 20  49 HU,  0.0'',  24 hrs Low Low Caution
Sat, May 21  55 HU,  0.0'',  20 hrs Low Low Caution
Sun, May 22  43 HU,  0.0'',  16 hrs Low Low Caution
Mon, May 23  32 HU,  0.40'',  24 hrs Low Low Caution
Tue, May 24  41 HU,  0.01'',  24 hrs Low Low Caution
Wed, May 25  103 HU,  0.0'',  13 hrs Low Caution (if dew) HIGH (if dew)
Thu, May 26  119 HU,  0.0'',  24 hrs Low Caution (if dew) HIGH (if dew)
Fri, May 27  160 HU,  0.0'',  19 hrs Caution (if dew) Caution (if dew) HIGH (if dew)
Sat, May 28  191 HU,  0.0'',  19 hrs Caution (if dew) Caution (if dew) HIGH (if dew)
Sun, May 29  160 HU,  0.0'',  24 hrs Caution (if dew) Caution (if dew) HIGH (if dew)
Mon, May 30  362 HU,  0.0'',  15 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Tue, May 31  498 HU,  0.0'',  10 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Wed, June 1  486 HU,  0.18'',  24 hrs Caution EXTREME! EXCEPTIONAL!
Thu, June 2  513 HU,  0.0'',  8 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Fri, June 3  312 HU,  0.0'',  0 hrs Low Low Low
Sat, June 4  149 HU,  0.0'',  0 hrs Low Low Low
Sun, June 5  121 HU,  0.02'',  10 hrs Low Caution HIGH
Mon, June 6  116 HU,  0.0'',  10 hrs Low Caution (if dew) HIGH (if dew)
Tue, June 7  328 HU,  0.0'',  5 hrs Caution (if dew) HIGH (if dew) EXCEPTIONAL! (if dew)
Wed, June 8  817 HU,  0.15'',  1 hrs EXTREME! EXCEPTIONAL! EXCEPTIONAL!
Thu, June 9  1047 HU,  0.42'',  16 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Fri, June 10  1134 HU,  0.04'',  13 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Sat, June 11  911 HU,  1.60'',  24 hrs EXTREME! EXCEPTIONAL! EXCEPTIONAL!
Sun, June 12  407 HU,  0.29'',  24 hrs Caution EXTREME! EXCEPTIONAL!
Mon, June 13  177 HU,  0.01'',  19 hrs Caution Caution HIGH
Tue, June 14  37 HU,  0.06'',  15 hrs Low Low Caution
Wed, June 15  74 HU,  0.0'',  1 hrs Low Low Low
Thu, June 16  195 HU,  0.0'',  5 hrs Caution (if dew) Caution (if dew) HIGH (if dew)
Fri, June 17  208 HU,  0.96'',  16 hrs Caution HIGH EXTREME!
Sat, June 18  295 HU,  0.0'',  13 hrs Caution (if dew) HIGH (if dew) EXTREME! (if dew)
Sun, June 19  352 HU,  0.0'',  3 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Mon, June 20  308 HU,  0.0'',  7 hrs Caution (if dew) HIGH (if dew) EXCEPTIONAL! (if dew)
Tue, June 21  422 HU,  0.0'',  4 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Wed, June 22  384 HU,  1.0'',  24 hrs Caution EXTREME! EXCEPTIONAL!
Thu, June 23  300 HU,  1.0'',  24 hrs Caution HIGH EXTREME!
Fri, June 24  238 HU,  0.02'',  24 hrs Caution HIGH EXTREME!
Sat, June 25  141 HU,  0.02'',  19 hrs Low Caution HIGH
Sun, June 26  142 HU,  0.0'',  24 hrs Low Caution (if dew) HIGH (if dew)
Mon, June 27  335 HU,  0.0'',  10 hrs Caution (if dew) HIGH (if dew) EXCEPTIONAL! (if dew)
Tue, June 28  471 HU,  0.15'',  15 hrs Caution EXTREME! EXCEPTIONAL!
Wed, June 29  701 HU,  0.0'',  13 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Thu, June 30  843 HU,  0.0'',  0 hrs Low Low Low
Fri, July 1  770 HU,  0.0'',  0 hrs Low Low Low
Sat, July 2  738 HU,  0.0'',  15 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Sun, July 3  578 HU,  0.03'',  24 hrs HIGH EXCEPTIONAL! EXCEPTIONAL!
Mon, July 4  650 HU,  0.0'',  12 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Tue, July 5  959 HU,  0.0'',  8 hrs EXTREME! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Wed, July 6  1069 HU,  0.0'',  9 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Thu, July 7  1354 HU,  0.10'',  12 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Fri, July 8  1206 HU,  1.96'',  24 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Sat, July 9  1150 HU,  0.0'',  11 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Sun, July 10  1134 HU,  0.0'',  0 hrs Low Low Low
Mon, July 11  1060 HU,  0.14'',  14 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!