Fireblight infection conditions - Cougarblight model

Background Information for this page
Return to radar list for Hancock NH
Weather data for Hancock NH.  Forecast values begin July 31, 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 24, then blossom blight would be noticeable by May 31, and shoot blight by June 9.
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
 Sat, May 14 
7 HU,  0.28'',  10 hrs Low Low Caution
Sun, May 15  10 HU,  1.27'',  24 hrs Low Low Caution
Mon, May 16  10 HU,  0.39'',  24 hrs Low Low Caution
Tue, May 17  11 HU,  0.51'',  24 hrs Low Low Caution
Wed, May 18  8 HU,  0.49'',  24 hrs Low Low Caution
Thu, May 19  15 HU,  0.14'',  24 hrs Low Low Caution
Fri, May 20  29 HU,  0.02'',  20 hrs Low Low Caution
Sat, May 21  51 HU,  0.23'',  23 hrs Low Low Caution
Sun, May 22  50 HU,  0.12'',  14 hrs Low Low Caution
Mon, May 23  50 HU,  0.20'',  22 hrs Low Low Caution
Tue, May 24  139 HU,  0.27'',  19 hrs Low Caution HIGH
Wed, May 25  212 HU,  0.0'',  10 hrs Caution (if dew) HIGH (if dew) EXTREME! (if dew)
Thu, May 26  468 HU,  0.0'',  3 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Fri, May 27  877 HU,  0.0'',  6 hrs EXTREME! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Sat, May 28  871 HU,  0.05'',  18 hrs EXTREME! EXCEPTIONAL! EXCEPTIONAL!
Sun, May 29  1143 HU,  0.0'',  8 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Mon, May 30  1269 HU,  0.0'',  0 hrs Low Low Low
Tue, May 31  1178 HU,  0.0'',  0 hrs Low Low Low
Wed, June 1  1387 HU,  0.36'',  10 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Thu, June 2  1030 HU,  0.02'',  5 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Fri, June 3  658 HU,  0.0'',  0 hrs Low Low Low
Sat, June 4  348 HU,  0.0'',  0 hrs Low Low Low
Sun, June 5  75 HU,  0.02'',  4 hrs Low Low Caution
Mon, June 6  245 HU,  0.0'',  10 hrs Caution (if dew) HIGH (if dew) EXTREME! (if dew)
Tue, June 7  602 HU,  0.0'',  0 hrs Low Low Low
Wed, June 8  1163 HU,  0.54'',  4 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Thu, June 9  1367 HU,  0.65'',  22 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Fri, June 10  1295 HU,  0.16'',  11 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Sat, June 11  930 HU,  0.97'',  22 hrs EXTREME! EXCEPTIONAL! EXCEPTIONAL!
Sun, June 12  354 HU,  0.0'',  24 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Mon, June 13  131 HU,  0.26'',  15 hrs Low Caution HIGH
Tue, June 14  26 HU,  0.11'',  24 hrs Low Low Caution
Wed, June 15  117 HU,  0.29'',  18 hrs Low Caution HIGH
Thu, June 16  446 HU,  0.0'',  10 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Fri, June 17  475 HU,  0.25'',  13 hrs Caution EXTREME! EXCEPTIONAL!
Sat, June 18  671 HU,  0.06'',  18 hrs HIGH EXCEPTIONAL! EXCEPTIONAL!
Sun, June 19  647 HU,  0.0'',  8 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Mon, June 20  478 HU,  0.0'',  0 hrs Low Low Low
Tue, June 21  702 HU,  0.0'',  0 hrs Low Low Low
Wed, June 22  534 HU,  2.05'',  14 hrs HIGH EXCEPTIONAL! EXCEPTIONAL!
Thu, June 23  477 HU,  0.41'',  24 hrs Caution EXTREME! EXCEPTIONAL!
Fri, June 24  319 HU,  0.35'',  24 hrs Caution HIGH EXCEPTIONAL!
Sat, June 25  75 HU,  0.23'',  24 hrs Low Low Caution
Sun, June 26  118 HU,  0.01'',  15 hrs Low Caution HIGH
Mon, June 27  398 HU,  0.0'',  10 hrs Caution (if dew) EXTREME! (if dew) EXCEPTIONAL! (if dew)
Tue, June 28  654 HU,  0.50'',  7 hrs HIGH EXCEPTIONAL! EXCEPTIONAL!
Wed, June 29  800 HU,  0.0'',  11 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Thu, June 30  860 HU,  0.0'',  0 hrs Low Low Low
Fri, July 1  683 HU,  0.0'',  0 hrs Low Low Low
Sat, July 2  670 HU,  0.0'',  8 hrs HIGH (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Sun, July 3  610 HU,  0.05'',  13 hrs HIGH EXCEPTIONAL! EXCEPTIONAL!
Mon, July 4  882 HU,  0.19'',  17 hrs EXTREME! EXCEPTIONAL! EXCEPTIONAL!
Tue, July 5  1203 HU,  0.0'',  10 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Wed, July 6  1396 HU,  0.36'',  7 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Thu, July 7  1544 HU,  0.0'',  10 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Fri, July 8  1241 HU,  0.21'',  8 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Sat, July 9  1026 HU,  0.0'',  10 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Sun, July 10  902 HU,  0.0'',  0 hrs Low Low Low
Mon, July 11  1323 HU,  0.0'',  0 hrs Low Low Low
Tue, July 12  1843 HU,  0.0'',  0 hrs Low Low Low
Wed, July 13  1850 HU,  0.47'',  7 hrs EXCEPTIONAL! EXCEPTIONAL! EXCEPTIONAL!
Thu, July 14  1652 HU,  0.0'',  10 hrs EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew) EXCEPTIONAL! (if dew)
Fri, July 15  1231 HU,  0.0'',  0 hrs Low Low Low