Basic information on primary and secondary apple scab infection periods
Background Information for this page
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Weather data for Easthampton MA.  Forecast values begin July 16, 2018
    Each expected ascospore release is tracked as a separate event.  Infection periods representing separate ascospore releases can overlap.  Wetting period duration is compared against the Revised MillsTable by MacHardy et al. for daytime rains during the primary scab season to estimate release of ascospores.  Wetting period duration for night-only rains during primary scab season, and after the completion of ascospore maturation (secondary scab season) are compared to the Jones revision of the Mills table to estimate if wetting was long enough for infection to occur.

     The increase in natural resistance to scab infection in the weeks after petal fall is not factored into the Mills table.  Because of this, some of the summer wetting periods rated as scab infection periods may in fact have been too sort to cause late season infections.  Dry hours in middle of a wet period are not counted toward duration of the wet period.  As a result, wetting period duration is not simply the difference between start and end times.

     The estimates shown below should only be used as supplements to on-site observations.
Wetting period following  April 19, 5 AM rain was too short for scab infection.
Infection period  1.    
  Begin: Wednesday, April 25 at 4 AM    --->     End: Saturday, April 28 at 3 PM.     
  Growth stage at start of period:  Between Green Tip and Quarter Inch Green    
  Best guess is that this infection period accounts for 0.7 % of the season's total primary scab infection risk.
Infection period  2.    
  Begin: Friday, April 27 at 11 AM    --->     End: Sunday, April 29 at 11 PM.     
  Growth stage at start of period:  Between Half Inch Green and Tight Cluster    
  Best guess is that this infection period accounts for 0.5 % of the season's total primary scab infection risk.
Infection period  3.    
  Begin: Saturday, April 28 at 11 PM    --->     End: Tuesday, May 01 at 3 PM.     
  Growth stage at start of period:  Between Half Inch Green and Tight Cluster    
  Best guess is that this infection period accounts for 0.4 % of the season's total primary scab infection risk.
Infection period  4.    
  Begin: Monday, April 30 at 8 AM    --->     End: Thursday, May 03 at 11 AM.     
  Growth stage at start of period:  Between Half Inch Green and Tight Cluster    
  Best guess is that this infection period accounts for 0.1 % of the season's total primary scab infection risk.
Infection period  5.    
  Begin: Thursday, May 03 at 6 PM    --->     End: Saturday, May 05 at 7 AM.     
  Growth stage at start of period:  Open Cluster    
  Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk.
Infection period  6.    
  Begin: Friday, May 04 at 8 PM    --->     End: Monday, May 07 at 2 PM.     
  Growth stage at start of period:  full Pink-extended    
  Best guess is that this infection period accounts for 0.2 % of the season's total primary scab infection risk.
Infection period  7.    
  Begin: Sunday, May 06 at 4 AM    --->     End: Tuesday, May 08 at 2 PM.     
  Growth stage at start of period:  Between Full Pink and King Bloom    
  Best guess is that this infection period accounts for 12 % of the season's total primary scab infection risk.
Infection period  8.    
  Begin: Saturday, May 12 at 10 AM    --->     End: Wednesday, May 16 at 3 PM.     
  Growth stage at start of period:  Between Full Bloom and Petal Fall    
  Best guess is that this infection period accounts for 17 % of the season's total primary scab infection risk.
Infection period  9.    
  Begin: Tuesday, May 15 at 11 AM    --->     End: Thursday, May 17 at 5 PM.     
  Growth stage at start of period:  Between Full Bloom and Petal Fall    
  Best guess is that this infection period accounts for 32 % of the season's total primary scab infection risk.
Infection period  10.    
  Begin: Saturday, May 19 at 9 AM    --->     End: Wednesday, May 23 at 3 PM.     
  Growth stage at start of period:  1 - 5 days after Petal Fall    
  Best guess is that this infection period accounts for 20 % of the season's total primary scab infection risk.
Infection period  11.    
  Begin: Tuesday, May 22 at 12 PM    --->     End: Friday, May 25 at 11 AM.     
  Growth stage at start of period:  Fruit Set    
  Best guess is that this infection period accounts for 4 % of the season's total primary scab infection risk.
Infection period  12.    
  Begin: Sunday, May 27 at 11 AM    --->     End: Tuesday, May 29 at 3 PM.     
  Growth stage at start of period:  6 or more days after Petal Fall    
  Best guess is that this infection period accounts for 8 % of the season's total primary scab infection risk.
Infection period  13.    
  Begin: Friday, June 01 at 11 AM    --->     End: Wednesday, June 06 at 3 PM.     
  Growth stage at start of period:  6 or more days after Petal Fall    
  Best guess is that this infection period accounts for 0.4 % of the season's total primary scab infection risk.
Infection period  14.    
  Begin: Monday, June 04 at 2 AM    --->     End: Thursday, June 07 at 4 PM.     
  Growth stage at start of period:  6 or more days after Petal Fall    
  Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk.
Infection period  15.    
  Begin: Wednesday, June 13 at 2 PM    --->     End: Friday, June 15 at 7 PM.     
      
  The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  16.    
  Begin: Friday, June 15 at 5 AM    --->     End: Saturday, June 16 at 1 PM.     
      
  The 18 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  17.    
  Begin: Monday, June 18 at 6 PM    --->     End: Thursday, June 21 at 2 PM.     
      
  The 22 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  18.    
  Begin: Saturday, June 23 at 2 AM    --->     End: Monday, June 25 at 2 PM.     
      
  The 50 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  19.    
  Begin: Sunday, June 24 at 2 PM    --->     End: Tuesday, June 26 at 11 AM.     
      
  The 22 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  20.    
  Begin: Wednesday, June 27 at 5 PM    --->     End: Sunday, July 01 at 10 AM.     
      
  The 41 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Wetting period following  July 06, 8 AM rain was too short for scab infection.
Infection period  21.    
  Begin: Sunday, July 15 at 1 AM    --->     End: Monday, July 16 at 3 PM.     
      
  The 19 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  22.    
  Begin: Tuesday, July 17 at 4 AM    --->     End: Friday, July 20 at 12 PM.     
      
  The 33 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.
Infection period  23.    
  Begin: Sunday, July 22 at 9 AM    --->     End: Saturday, July 28 at 1 PM.     
      
  The 100 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.