Fireblight infection conditions - Eastern model

Background Information for this page
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Weather data for Westhampton MA.  Forecast values begin September 18, 2018
     This table shows estimates of RELATIVE daily fire blight blossom infection risk based on weather conditions.  Rating criteria are derived from the work of Dr. Paul W. Steiner and Gary W. Lightner at the University of Maryland. 
      ABSOLUTE risk depends on the amount of fire blight bacteria in the area, the number of open flowers, age (trees < 6 years old most vulnerable), 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.   
      Individual cutltivar may start bloom a day or two later, or finish a day or two earlier, than full range of open blossom dates shown. Gray shading indicates dates when most trees will have lost open blossoms, but late blooming cultivars or young trees may still have open flowers and be susceptible to blossom blight.  
      Fireblight infection can occur without rain if there is "heavy" dew.  If there are enough heat units for infection but no rain, if leaves are expected to be wet for 2 or more hours, then infection risk is reported with "if dew" attached.  Infection potential "dew risk" days is not well understood.  Infection potential may increase with high relative humidty prior to and during infection events, and be reduced by an extended period of low relative humidity.
Shoots near overwintered fire blight cankers would start showing obvious symptoms around
 Friday, June 1
 If canker blight infection spreads to other shoots,
symptoms on those secondary shoot infections would become obvious around Thursday, June 14
Open blossom dates for common cultivars.
"Date" is from 8am to 8am the following day, not midnight to midnight.
Cumulative Fire blight bacteria potential (FBP).
100% = minimum threshold level for infection.

Cumulative % FBP,
(single day value),
Inches Rain,
Leaf Wet Hours
Values are for 8am to 8am the next day.
          In absence of rain, 3 or more hours of leaf wetness is counted as possible dew conditions for adequate wetting, which may overstate risk on such days. See Cougarblight model for additional comments.
Eastern Fire blight Model Rating
Infection Requirements:
100% FBP
(>198 degree hours > 65F), &
> 0" rain, or > 0.1 inch rain on previous day.
SEVERE RISK = 200% FBP and wetting.
Dates
Blossom Blight
(& Shoot Blight) would be obvious if infection occurred
possible early cultivar
King Bloom: May 7 
10% (10%),  0.0'',  7 hrs.  No blossom infection  
McIntosh King Bloom:
Tue, May 8 
36% (26%),  0.0'',  2 hrs.  No blossom infection  
Wed, May 9  83% (46%),  0.0'',  0 hrs.  No blossom infection  
Thu, May 10  91% (9%),  0.0'',  0 hrs.  No blossom infection  
Fri, May 11  95% (4%),  0.0'',  0 hrs.  No blossom infection  
Sat, May 12  64% (0%),  0.24'',  22 hrs.  No blossom infection  
Sun, May 13  39% (0%),  0.0'',  4 hrs.  No blossom infection  
Mon, May 14  34% (22%),  0.0'',  4 hrs.  No blossom infection  
Tue, May 15  59% (34%),  0.96'',  24 hrs.  No blossom infection  
Wed, May 16  56% (0%),  0.0'',  9 hrs.  No blossom infection  
McIntosh 95% Petal Fall
on Thu, May 17 
87% (31%),  0.0'',  5 hrs.  No blossom infection  
McIntosh 100% Petal Fall
on Fri, May 18 
68% (3%),  0.0'',  0 hrs.  No blossom infection  
Sat, May 19  45% (0%),  0.52'',  23 hrs.  No blossom infection  
Sun, May 20  71% (37%),  0.08'',  24 hrs.  No blossom infection  
Mon, May 21  110% (39%),  0.0'',  1 hrs.  Infection Potential
(dew risk)
May 31, (June 11)
Late Cultivar Petal Fall
on Tue, May 22 
53% (0%),  0.09'',  20 hrs.  No blossom infection  
Wed, May 23  121% (68%),  0.0'',  3 hrs.  Infection Potential
(dew risk)
June 1, (June 13)
Thu, May 24  158% (50%),  0.0'',  0 hrs.  Infection Potential
(if wetting)
June 1, (June 13)
Fri, May 25  226% (108%),  0.0'',  0 hrs.  SEVERE Infection Potential
(if wetting)
June 2, (June 16)
Sat, May 26  284% (126%),  0.0'',  0 hrs.  SEVERE Infection Potential
(if wetting)
June 7, (June 17)
Sun, May 27  234% (0%),  0.29'',  21 hrs.  SEVERE INFECTION RISK! June 7, (June 17)
Mon, May 28  239% (5%),  0.0'',  14 hrs.  SEVERE INFECTION RISK! June 8, (June 17)
Tue, May 29  232% (102%),  0.0'',  7 hrs.  SEVERE Infection Potential
(Dew Risk)
June 9, (June 18)
Wed, May 30  178% (72%),  0.0'',  0 hrs.  Infection Potential
(if wetting)
June 11, (June 19)
Thu, May 31  240% (67%),  0.0'',  7 hrs.  SEVERE Infection Potential
(Dew Risk)
June 12, (June 20)
Fri, June 1  226% (87%),  0.03'',  24 hrs.  SEVERE INFECTION RISK! June 14, (June 21)
Sat, June 2  242% (88%),  0.0'',  3 hrs.  SEVERE Infection Potential
(Dew Risk)
June 16, (June 22)
Sun, June 3  187% (11%),  0.48'',  6 hrs.  INFECTION RISK June 16, (June 23)
Mon, June 4  125% (0%),  0.33'',  24 hrs.  INFECTION RISK June 16, (June 23)
Tue, June 5  84% (0%),  0.05'',  21 hrs.  No blossom infection  
Wed, June 6  88% (4%),  0.0'',  8 hrs.  No blossom infection  
Thu, June 7  28% (13%),  0.0'',  8 hrs.  No blossom infection  
Fri, June 8  75% (59%),  0.0'',  8 hrs.  No blossom infection  
Sat, June 9  133% (58%),  0.0'',  0 hrs.  Infection Potential
(if wetting)
June 18, (June 27)
Sun, June 10  158% (29%),  0.0'',  0 hrs.  Infection Potential
(if wetting)
June 18, (June 27)
Mon, June 11  169% (24%),  0.0'',  0 hrs.  Infection Potential
(if wetting)
June 19, (June 28)
Tue, June 12  160% (49%),  0.0'',  0 hrs.  Infection Potential
(if wetting)
June 20, (June 29)
Wed, June 13  139% (37%),  0.01'',  3 hrs.  INFECTION RISK June 21, (June 29)
Thu, June 14  125% (39%),  0.03'',  3 hrs.  INFECTION RISK June 22, (June 30)
Fri, June 15  135% (10%),  0.01'',  14 hrs.  INFECTION RISK June 22, (June 30)
Sat, June 16  165% (79%),  0.0'',  1 hrs.  Infection Potential
(dew risk)
June 24, (July 1)
Sun, June 17  204% (115%),  0.0'',  0 hrs.  SEVERE Infection Potential
(if wetting)
June 26, (July 1)
Mon, June 18  351% (156%),  1.01'',  15 hrs.  SEVERE INFECTION RISK! June 27, (July 2)
Tue, June 19  352% (81%),  0.0'',  1 hrs.  SEVERE INFECTION RISK! June 28, (July 3)
Wed, June 20  295% (58%),  0.0'',  5 hrs.  SEVERE Infection Potential
(Dew Risk)
June 29, (July 3)
Thu, June 21  214% (75%),  0.0'',  2 hrs.  SEVERE Infection Potential
(Dew Risk)
June 30, (July 4)
Fri, June 22  182% (49%),  0.02'',  6 hrs.  INFECTION RISK June 30, (July 4)
Sat, June 23  122% (0%),  0.01'',  17 hrs.  INFECTION RISK June 30, (July 4)
Sun, June 24  168% (45%),  1.43'',  24 hrs.  INFECTION RISK July 1, (July 5)