Basic information on primary and secondary apple scab infection periods
Background Information for this page
Return to Apple list for Greenville RI
Weather data for Greenville RI.  Forecast values begin April 27, 2015
    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.
Infection period  1.    
  Begin: Monday, April 20 at 7 AM    --->     End: Thursday, April 23 at 12 PM.     
  Growth stage at start of period:  Between Green Tip and Quarter Inch Green    
  Best guess is that this infection period accounts for 0.6 % of the season's total primary scab infection risk.
Wetting period following  April 22, 8 PM rain was too short for scab infection.
Infection period  2.    
  Begin: Monday, April 27 at 7 PM    --->     End: Thursday, April 30 at 1 PM.     
  Growth stage at start of period:  Between Half Inch Green and Tight Cluster    
  Best guess is that this infection period accounts for less than 0.1 % of the season's total primary scab infection risk.
Infection period  3.    
  Begin: Thursday, April 30 at 6 PM    --->     End: Sunday, May 03 at 1 PM.     
  Growth stage at start of period:  Between Half Inch Green and Tight Cluster    
  Best guess is that this infection period accounts for 3 % of the season's total primary scab infection risk.