Basic information on primary and secondary apple scab infection periods

Background Information for this page

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Weather data for Monmouth ME.  Forecast values begin October 7, 2008

Each expected ascospore release is tracked as a separate event.  Infection periods representing separate ascospore releases can overlap.  Growers counting infection periods for the Delayed First-Spray Strategy can consider infection periods separated by less than 24 hours of dry leaves as a single prolonged infection period, as described in the New England Apple Pest Management Guide.           Wetting period duration is compared against the Revised MillsTable by MacHardy et al. for daytime rains during the primary scab season (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 evaluated with the Jones revision of the Mills table.      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 23, 11 PM rain was too short for scab infection.

Infection period  1.       Begin: Sunday, April 27 at 8 AM    --->     End: Thursday, May 01 at 8 AM.        Growth stage at start of period:  Between Half Inch Green and Tight Cluster       Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk.

Infection period  2.       Begin: Saturday, May 03 at 12 PM    --->     End: Tuesday, May 06 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 2 % of the season's total primary scab infection risk.

Wetting period following  May 08, 2 AM rain was too short for scab infection.

Wetting period following  May 17, 4 AM rain was too short for scab infection.

Wetting period following  May 19, 8 AM rain was too short for scab infection.

Wetting period following  May 19, 7 PM rain was too short for scab infection.

Infection period  3.       Begin: Wednesday, May 21 at 4 PM    --->     End: Friday, May 23 at 12 PM.        Growth stage at start of period:  Between King Bloom and Full Bloom       Best guess is that this infection period accounts for 40 % of the season's total primary scab infection risk.

Infection period  4.       Begin: Thursday, May 22 at 5 PM    --->     End: Saturday, May 24 at 11 AM.        Growth stage at start of period:  Full Bloom       Best guess is that this infection period accounts for 12 % of the season's total primary scab infection risk.

Infection period  5.       Begin: Friday, May 23 at 2 PM    --->     End: Sunday, May 25 at 8 AM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Best guess is that this infection period accounts for 13 % of the season's total primary scab infection risk.

Wetting period following  May 27, 2 PM rain was too short for scab infection.

Infection period  6.       Begin: Saturday, May 31 at 2 AM    --->     End: Monday, June 02 at 3 PM.        Growth stage at start of period:  1 - 5 days after Petal Fall       Best guess is that this infection period accounts for 24 % of the season's total primary scab infection risk.

Infection period  7.       Begin: Monday, June 02 at 5 AM    --->     End: Thursday, June 05 at 8 PM.        Growth stage at start of period:  Fruit Set       Best guess is that this infection period accounts for less than 0.1 % of the season's total primary scab infection risk.

Infection period  8.       Begin: Tuesday, June 03 at 12 PM    --->     End: Saturday, June 07 at 5 PM.        Growth stage at start of period:  6 or more days after Petal Fall       Best guess is that this infection period accounts for 6 % of the season's total primary scab infection risk.

Infection period  9.       Begin: Friday, June 06 at 7 AM    --->     End: Sunday, June 08 at 2 PM.               The 31 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  10.       Begin: Tuesday, June 10 at 5 PM    --->     End: Thursday, June 12 at 11 AM.               The 18 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  11.       Begin: Sunday, June 15 at 12 AM    --->     End: Wednesday, June 18 at 5 PM.               The 78 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  12.       Begin: Wednesday, June 18 at 2 AM    --->     End: Thursday, June 19 at 6 PM.               The 27 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  13.       Begin: Thursday, June 19 at 11 AM    --->     End: Saturday, June 21 at 3 PM.               The 38 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  14.       Begin: Friday, June 20 at 2 PM    --->     End: Tuesday, June 24 at 3 PM.               The 79 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  15.       Begin: Sunday, June 22 at 2 PM    --->     End: Wednesday, June 25 at 11 AM.               The 61 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  16.       Begin: Tuesday, June 24 at 5 PM    --->     End: Thursday, June 26 at 8 AM.               The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  17.       Begin: Thursday, June 26 at 11 PM    --->     End: Tuesday, July 01 at 1 PM.               The 97 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  18.       Begin: Thursday, July 03 at 2 PM    --->     End: Saturday, July 05 at 2 PM.               The 26 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  19.       Begin: Wednesday, July 09 at 5 PM    --->     End: Friday, July 11 at 10 AM.               The 17 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  20.       Begin: Monday, July 14 at 4 AM    --->     End: Tuesday, July 15 at 12 PM.               The 19 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  21.       Begin: Friday, July 18 at 11 AM    --->     End: Tuesday, July 22 at 6 PM.               The 95 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  22.       Begin: Saturday, July 19 at 5 PM    --->     End: Friday, July 25 at 4 PM.               The 128 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  23.       Begin: Wednesday, July 23 at 3 PM    --->     End: Saturday, July 26 at 3 PM.               The 58 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  24.       Begin: Sunday, July 27 at 6 PM    --->     End: Tuesday, July 29 at 2 PM.               The 29 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  25.       Begin: Tuesday, July 29 at 5 PM    --->     End: Tuesday, August 05 at 2 PM.               The 145 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  26.       Begin: Thursday, July 31 at 8 AM    --->     End: Saturday, August 09 at 5 PM.               The 217 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  27.       Begin: Tuesday, August 05 at 4 PM    --->     End: Sunday, August 10 at 5 PM.               The 107 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  28.       Begin: Monday, August 11 at 1 PM    --->     End: Thursday, August 14 at 6 PM.               The 61 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  29.       Begin: Saturday, August 16 at 1 PM    --->     End: Monday, August 18 at 2 PM.               The 31 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  30.       Begin: Monday, August 18 at 11 PM    --->     End: Wednesday, August 20 at 4 PM.               The 17 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  31.       Begin: Saturday, September 06 at 8 AM    --->     End: Monday, September 08 at 12 PM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  32.       Begin: Tuesday, September 09 at 8 AM    --->     End: Thursday, September 11 at 1 PM.               The 32 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  33.       Begin: Friday, September 12 at 1 PM    --->     End: Monday, September 15 at 1 PM.               The 63 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  34.       Begin: Sunday, September 14 at 5 AM    --->     End: Tuesday, September 16 at 10 AM.               The 29 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.