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 May 21, 2012
     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 estimate varies 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 22, then blossom blight would be noticeable by June 2, and shoot blight by June 12.
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.
McIntosh King Bloom
 Tue, April 24 
0 HU,  0.0'',  5 hrs Low Low Caution
Wed, April 25  2 HU,  0.0'',  0 hrs Low Low Low
Thu, April 26  5 HU,  0.0'',  1 hrs Low Low Low
Fri, April 27  6 HU,  0.0'',  8 hrs Low Low Caution
Sat, April 28  8 HU,  0.0'',  0 hrs Low Low Low
Sun, April 29  8 HU,  0.0'',  0 hrs Low Low Low
Mon, April 30  6 HU,  0.05'',  0 hrs Low Low Caution
Tue, May 1  5 HU,  0.59'',  20 hrs Low Low Caution
Wed, May 2  5 HU,  0.13'',  14 hrs Low Low Caution
Thu, May 3  2 HU,  0.03'',  21 hrs Low Low Caution
Fri, May 4  3 HU,  0.01'',  24 hrs Low Low Caution
Sat, May 5  6 HU,  0.0'',  24 hrs Low Low Caution
Sun, May 6  8 HU,  0.0'',  12 hrs Low Low Caution
Mon, May 7  14 HU,  0.0'',  8 hrs Low Low Caution
Tue, May 8  17 HU,  0.55'',  1 hrs Low Low Caution
Wed, May 9  22 HU,  1.67'',  24 hrs Low Low Caution
Thu, May 10  25 HU,  0.03'',  14 hrs Low Low Caution
Fri, May 11  24 HU,  0.0'',  0 hrs Low Low Low
Sat, May 12  45 HU,  0.0'',  0 hrs Low Low Low
Sun, May 13  66 HU,  0.0'',  0 hrs Low Low Low
Mon, May 14  83 HU,  0.0'',  0 hrs Low Low Low
Tue, May 15  92 HU,  1.16'',  10 hrs Low Low Caution
Wed, May 16  77 HU,  0.45'',  24 hrs Low Low Caution
Thu, May 17  66 HU,  0.0'',  8 hrs Low Low Caution
Fri, May 18  54 HU,  0.0'',  4 hrs Low Low Caution
Sat, May 19  79 HU,  0.0'',  0 hrs Low Low Low
Sun, May 20  101 HU,  0.0'',  0 hrs Low Low Low
Mon, May 21  98 HU,  0.18'',  17 hrs Low Low Caution
Tue, May 22  111 HU,  0.05'',  24 hrs Low Caution HIGH
Wed, May 23  116 HU,  0.0'',  12 hrs Low Caution (if dew) HIGH (if dew)
Thu, May 24  157 HU,  0.0'',  0 hrs Low Low Low
Fri, May 25  208 HU,  0.0'',  0 hrs Low Low Low
Sat, May 26  271 HU,  0.0'',  0 hrs Low Low Low
Sun, May 27  277 HU,  0.0'',  0 hrs Low Low Low
Mon, May 28  237 HU,  0.0'',  0 hrs Low Low Low