Basic information on primary and secondary apple scab infection periods

Background Information for this page

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Weather data for Sanford ME.  Forecast values begin November 1, 2011

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 Tree Fruit 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.

Infection period  1.       Begin: Saturday, April 23 at 6 AM    --->     End: Wednesday, April 27 at 4 PM.        Growth stage at start of period:  Between Green Tip and Quarter Inch Green       Best guess is that this infection period accounts for 0.1 % of the season's total primary scab infection risk.

Infection period  2.       Begin: Monday, April 25 at 5 PM    --->     End: Friday, April 29 at 11 AM.        Growth stage at start of period:  Between Green Tip and Quarter Inch Green       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 28 at 2 PM    --->     End: Sunday, May 01 at 7 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  4.       Begin: Wednesday, May 04 at 7 AM    --->     End: Saturday, May 07 at 12 PM.        Growth stage at start of period:  Between Open Cluster and Full Pink       Best guess is that this infection period accounts for 3 % of the season's total primary scab infection risk.

Infection period  5.       Begin: Saturday, May 07 at 1 PM    --->     End: Monday, May 09 at 10 AM.        Growth stage at start of period:  Between Open Cluster and Full Pink       Best guess is that this infection period accounts for 8 % of the season's total primary scab infection risk.

Infection period  6.       Begin: Sunday, May 08 at 2 PM    --->     End: Wednesday, May 11 at 3 PM.        Growth stage at start of period:  Between Open Cluster and Full Pink       Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk.

Infection period  7.       Begin: Tuesday, May 10 at 8 PM    --->     End: Friday, May 13 at 1 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  8.       Begin: Saturday, May 14 at 8 PM    --->     End: Tuesday, May 24 at 3 PM.        Growth stage at start of period:  Between Full Pink and King Bloom       Best guess is that this infection period accounts for 63 % of the season's total primary scab infection risk.

Infection period  9.       Begin: Monday, May 23 at 2 AM    --->     End: Wednesday, May 25 at 1 PM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Best guess is that this infection period accounts for 7 % of the season's total primary scab infection risk.

Infection period  10.       Begin: Tuesday, May 24 at 5 PM    --->     End: Thursday, May 26 at 1 PM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Best guess is that this infection period accounts for 6 % of the season's total primary scab infection risk.

Wetting period following  June 01, 8 AM rain was too short for scab infection.

Infection period  11.       Begin: Thursday, June 09 at 2 PM    --->     End: Monday, June 13 at 6 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  12.       Begin: Saturday, June 11 at 8 AM    --->     End: Tuesday, June 14 at 3 PM.               The 67 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  13.       Begin: Tuesday, June 14 at 2 AM    --->     End: Wednesday, June 15 at 12 PM.               Next infection period starts on same day, see next infection period for combined ratings.

Infection period  14.       Begin: Tuesday, June 14 at 5 PM    --->     End: Thursday, June 16 at 10 AM.               The 44 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  15.       Begin: Friday, June 17 at 2 PM    --->     End: Sunday, June 19 at 11 AM.               The 37 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  16.       Begin: Saturday, June 18 at 5 PM    --->     End: Tuesday, June 21 at 7 AM.               The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  17.       Begin: Wednesday, June 22 at 2 PM    --->     End: Monday, June 27 at 1 PM.               The 106 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  18.       Begin: Wednesday, June 29 at 2 AM    --->     End: Friday, July 01 at 11 AM.               The 10 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  19.       Begin: Friday, July 01 at 2 PM    --->     End: Sunday, July 03 at 2 PM.               The 27 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  20.       Begin: Sunday, July 03 at 5 PM    --->     End: Wednesday, July 06 at 10 AM.               The 40 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  21.       Begin: Wednesday, July 06 at 7 PM    --->     End: Saturday, July 09 at 1 PM.               The 27 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  22.       Begin: Friday, July 08 at 10 PM    --->     End: Monday, July 11 at 9 AM.               The 12 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  23.       Begin: Wednesday, July 13 at 2 PM    --->     End: Friday, July 15 at 10 AM.               The 21 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  24.       Begin: Monday, July 18 at 11 AM    --->     End: Thursday, July 21 at 9 AM.               The 20 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  25.       Begin: Saturday, July 23 at 5 AM    --->     End: Monday, July 25 at 10 AM.               The 6 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  26.       Begin: Monday, July 25 at 2 PM    --->     End: Thursday, July 28 at 11 AM.               The 47 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  27.       Begin: Friday, July 29 at 6 PM    --->     End: Sunday, July 31 at 11 AM.               The 18 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  28.       Begin: Tuesday, August 02 at 5 PM    --->     End: Thursday, August 04 at 1 PM.               The 24 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  29.       Begin: Friday, August 05 at 1 AM    --->     End: Saturday, August 06 at 2 PM.               The 21 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  30.       Begin: Saturday, August 06 at 11 PM    --->     End: Tuesday, August 09 at 1 PM.               The 55 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  31.       Begin: Monday, August 08 at 6 PM    --->     End: Thursday, August 11 at 1 PM.               The 54 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  32.       Begin: Tuesday, August 09 at 8 PM    --->     End: Saturday, August 13 at 1 PM.               The 47 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  33.       Begin: Sunday, August 14 at 10 PM    --->     End: Thursday, August 18 at 2 PM.               The 71 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  34.       Begin: Friday, August 19 at 5 PM    --->     End: Monday, August 22 at 1 PM.               The 49 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  35.       Begin: Sunday, August 21 at 2 PM    --->     End: Wednesday, August 24 at 12 PM.               The 25 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  36.       Begin: Thursday, August 25 at 8 AM    --->     End: Saturday, August 27 at 3 PM.               The 38 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  37.       Begin: Saturday, August 27 at 5 PM    --->     End: Tuesday, August 30 at 1 PM.               The 47 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  38.       Begin: Monday, September 05 at 6 AM    --->     End: Friday, September 09 at 3 PM.               The 94 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  39.       Begin: Tuesday, September 06 at 11 PM    --->     End: Saturday, September 10 at 12 PM.               The 65 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  40.       Begin: Thursday, September 15 at 8 AM    --->     End: Saturday, September 17 at 12 PM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  41.       Begin: Tuesday, September 20 at 8 AM    --->     End: Sunday, September 25 at 4 PM.               The 115 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  42.       Begin: Thursday, September 22 at 2 AM    --->     End: Monday, September 26 at 2 PM.               The 96 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.