Fireblight infection conditions - Cougarblight model

Background Information for this page
Return to radar list for Greenville RI
Weather data for Greenville RI.  Forecast values begin August 3, 2008
     Weather-based RELATIVE daily fireblight blossom infection risk values below are according to criteria of the Cougarblight model developed in Washington state by Dr. Timothy J. Smith.     
      ABSOLUTE risk also depends on cultivar and rootstock susceptibility, and on the number of flowers open. Infection risk may be overstated for first few days of bloom because fire blight bacteria may not have been distributed to open flowers.
      Cougarblight heat units are similar to degree hours base 60 F.
   
NOTICE! - Fireblight infection can occur without rain if there is "heavy" dew.  But "heavy" dew in relation to fireblight is not defined.  As a rough guess, if there is no rain on a day, but leaf wetness is expected to exceed 3 hours for that day, then infection conditions are reported with "if dew" attached.  Infection potential may be overstated on days when the "if dew" tag is attached.
Range of
potential
open-blossom dates
Gray box indicates dates when most trees will have lost open blossoms and susceptibility to blossom infection.  Gray box dates included for late cultivars and late-blooming young trees.
Fire blight risk categories by block history
 I  = No FB in the area during last two seasons
      requires 500+ heat units for HIGH! rating, 800+ for EXTREME!

 
II = FB present in the area, but not within 1 mile of your orchard last
    year requires 400+ heat units for HIGH! rating, 650+ for EXTREME!

 
III = FB in this orchard block or neighboring orchard last year
      requires 300+ heat units for HIGH! rating, 500+ for EXTREME!

 
IV = Active FB strikes or cankers present in this or neighboring block
      requires 200+ heat units for HIGH! rating, 350+ for EXTREME!
   If fire blight blossom infection occurred on May 8, then blossom blight would be noticeable by June 1, and shoot blight by June 10.
Inches Rain &
Leaf Wet Hours &
Heat Units
No FB in area for last two years
I
FB in area
last year,
but over 1 mile away
II
FB last year within 1 mile
III
Currently active FB
IV
Mon, May 5    0.'',  10 hrs.,  16 HU Low Low Low Low
Tue, May 6    0.'',  0 hrs.,  78 HU 0 0 0 0
Wed, May 7    0.'',  0 hrs.,  148 HU 0 0 0 0
Thu, May 8    0.13'',  12 hrs.,  222 HU Low Low Marginal HIGH!
Fri, May 9    0.38'',  16 hrs.,  206 HU Low Low Marginal HIGH!
Sat, May 10    0.'',  9 hrs.,  144 HU Low Low Low Marginal
(if dew)
Sun, May 11    0.'',  0 hrs.,  75 HU 0 0 0 0
Mon, May 12    0.'',  0 hrs.,  0 HU 0 0 0 0
Tue, May 13    0.'',  0 hrs.,  26 HU 0 0 0 0
Wed, May 14    0.'',  0 hrs.,  52 HU 0 0 0 0
Thu, May 15    0.'',  0 hrs.,  69 HU 0 0 0 0
Fri, May 16    0.41'',  10 hrs.,  69 HU Low Low Low Low
Sat, May 17    0.44'',  10 hrs.,  106 HU Low Low Low Marginal
Sun, May 18    0.05'',  8 hrs.,  102 HU Low Low Low Marginal
Mon, May 19    0.'',  7 hrs.,  85 HU Low Low Low Low
Tue, May 20    0.28'',  8 hrs.,  85 HU Low Low Low Low
Wed, May 21    0.'',  9 hrs.,  43 HU Low Low Low Low
Thu, May 22    0.03'',  7 hrs.,  21 HU Low Low Low Low
Fri, May 23    0.'',  0 hrs.,  60 HU 0 0 0 0
Sat, May 24    0.'',  0 hrs.,  98 HU 0 0 0 0
Sun, May 25    0.'',  0 hrs.,  180 HU 0 0 0 0
Mon, May 26    0.'',  0 hrs.,  320 HU 0 0 0 0
Tue, May 27    0.17'',  14 hrs.,  414 HU Marginal HIGH! HIGH! EXTREME!
Wed, May 28    0.'',  3 hrs.,  391 HU Low Marginal
(if dew)
HIGH!
(if dew)
EXTREME!
(if dew)
Thu, May 29    0.'',  0 hrs.,  407 HU 0 0 0 0
Fri, May 30    0.'',  0 hrs.,  382 HU 0 0 0 0
Sat, May 31    0.21'',  7 hrs.,  304 HU Low Low HIGH! HIGH!
Sun, June 1    0.'',  10 hrs.,  480 HU Marginal
(if dew)
HIGH!
(if dew)
HIGH!
(if dew)
EXTREME!
(if dew)
Mon, June 2    0.'',  0 hrs.,  519 HU 0 0 0 0
Tue, June 3    0.'',  0 hrs.,  677 HU 0 0 0 0
Wed, June 4    0.5'',  19 hrs.,  634 HU HIGH! HIGH! EXTREME! EXTREME!
Thu, June 5    0.03'',  24 hrs.,  442 HU Marginal HIGH! HIGH! EXTREME!
Fri, June 6    0.38'',  24 hrs.,  285 HU Low Low Marginal HIGH!
Sat, June 7    0.'',  12 hrs.,  337 HU Low Low HIGH!
(if dew)
HIGH!
(if dew)
Sun, June 8    0.'',  0 hrs.,  832 HU 0 0 0 0
Mon, June 9    0.'',  0 hrs.,  1348 HU 0 0 0 0
Tue, June 10    0.'',  0 hrs.,  1860 HU 0 0 0 0
Wed, June 11    0.'',  0 hrs.,  1953 HU 0 0 0 0
Thu, June 12    0.'',  0 hrs.,  1713 HU 0 0 0 0