Basic information on primary and secondary apple scab infection periods

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Weather data for Greenville RI.  Forecast values begin October 14, 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: Tuesday, April 12 at 11 AM    --->     End: Saturday, April 16 at 10 AM.        Growth stage at start of period:  Between Green Tip and Quarter Inch Green       Best guess is that this infection period accounts for 0.4 % of the season's total primary scab infection risk.

Infection period  2.       Begin: Saturday, April 16 at 6 PM    --->     End: Monday, April 18 at 5 AM.        Growth stage at start of period:  Between Quarter Inch Green and Half 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: Sunday, April 17 at 11 PM    --->     End: Thursday, April 21 at 11 AM.        Growth stage at start of period:  Half-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  4.       Begin: Tuesday, April 19 at 2 PM    --->     End: Sunday, April 24 at 2 PM.        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: Saturday, April 23 at 5 AM    --->     End: Monday, April 25 at 10 AM.        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.

Infection period  6.       Begin: Sunday, April 24 at 8 PM    --->     End: Tuesday, April 26 at 5 PM.        Growth stage at start of period:  early Tight Cluster       Best guess is that this infection period accounts for 0.1 % of the season's total primary scab infection risk.

Infection period  7.       Begin: Wednesday, April 27 at 7 PM    --->     End: Sunday, May 01 at 8 AM.        Growth stage at start of period:  Open Cluster       Best guess is that this infection period accounts for 13 % of the season's total primary scab infection risk.

Infection period  8.       Begin: Wednesday, May 04 at 2 PM    --->     End: Saturday, May 07 at 8 AM.        Growth stage at start of period:  Between King Bloom and Full Bloom       Best guess is that this infection period accounts for 22 % of the season's total primary scab infection risk.

Infection period  9.       Begin: Saturday, May 07 at 2 PM    --->     End: Tuesday, May 10 at 4 PM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Best guess is that this infection period accounts for 18 % of the season's total primary scab infection risk.

Infection period  10.       Begin: Tuesday, May 10 at 9 AM    --->     End: Wednesday, May 11 at 4 PM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Next infection period starts on same day, see next infection period for combined ratings.

Infection period  11.       Begin: Tuesday, May 10 at 11 PM    --->     End: Friday, May 13 at 12 PM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk.

Infection period  12.       Begin: Saturday, May 14 at 8 PM    --->     End: Sunday, May 22 at 5 PM.        Growth stage at start of period:  100% Petal Fall       Best guess is that this infection period accounts for 38 % of the season's total primary scab infection risk.

Infection period  13.       Begin: Monday, May 23 at 2 AM    --->     End: Wednesday, May 25 at 7 AM.        Growth stage at start of period:  6 or more days after Petal Fall       Best guess is that this infection period accounts for 1 % of the season's total primary scab infection risk.

Infection period  14.       Begin: Tuesday, May 24 at 11 PM    --->     End: Thursday, May 26 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 less than 0.1 % of the season's total primary scab infection risk.

Infection period  15.       Begin: Wednesday, June 01 at 8 AM    --->     End: Thursday, June 02 at 11 AM.        Growth stage at start of period:  6 or more days after Petal Fall       Next infection period starts on same day, see next infection period for combined ratings.

Infection period  16.       Begin: Wednesday, June 01 at 5 PM    --->     End: Saturday, June 04 at 7 AM.        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.

Wetting period following  June 05, 9 PM rain was too short for scab infection.

Infection period  17.       Begin: Wednesday, June 08 at 11 PM    --->     End: Friday, June 10 at 2 PM.               The 30 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  18.       Begin: Thursday, June 09 at 5 PM    --->     End: Monday, June 13 at 4 PM.               The 77 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  19.       Begin: Saturday, June 11 at 2 AM    --->     End: Tuesday, June 14 at 6 PM.               The 72 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  20.       Begin: Tuesday, June 14 at 2 AM    --->     End: Thursday, June 16 at 2 PM.               The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  21.       Begin: Friday, June 17 at 8 AM    --->     End: Monday, June 20 at 11 AM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  22.       Begin: Wednesday, June 22 at 10 AM    --->     End: Sunday, June 26 at 4 PM.               The 95 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  23.       Begin: Saturday, June 25 at 8 PM    --->     End: Tuesday, June 28 at 1 PM.               The 23 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Wetting period following  June 29, 4 AM rain was too short for scab infection.

Infection period  24.       Begin: Friday, July 01 at 8 PM    --->     End: Sunday, July 03 at 1 PM.               The 20 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  25.       Begin: Sunday, July 03 at 3 PM    --->     End: Wednesday, July 06 at 10 AM.               The 20 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  26.       Begin: Friday, July 08 at 6 AM    --->     End: Monday, July 11 at 11 AM.               The 32 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  27.       Begin: Tuesday, July 12 at 2 AM    --->     End: Thursday, July 14 at 12 PM.               The 24 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  28.       Begin: Wednesday, July 13 at 5 PM    --->     End: Saturday, July 16 at 8 AM.               The 16 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  29.       Begin: Monday, July 18 at 5 PM    --->     End: Thursday, July 21 at 1 PM.               The 23 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  30.       Begin: Saturday, July 23 at 11 AM    --->     End: Tuesday, July 26 at 4 PM.               The 36 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  31.       Begin: Monday, July 25 at 2 AM    --->     End: Wednesday, July 27 at 12 PM.               The 49 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  32.       Begin: Tuesday, July 26 at 5 PM    --->     End: Friday, July 29 at 6 PM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  33.       Begin: Friday, July 29 at 9 PM    --->     End: Monday, August 01 at 9 AM.               The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  34.       Begin: Tuesday, August 02 at 5 PM    --->     End: Thursday, August 04 at 12 PM.               The 21 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  35.       Begin: Saturday, August 06 at 8 PM    --->     End: Wednesday, August 10 at 3 PM.               The 81 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  36.       Begin: Monday, August 08 at 4 PM    --->     End: Thursday, August 11 at 1 PM.               The 58 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  37.       Begin: Wednesday, August 10 at 5 PM    --->     End: Saturday, August 13 at 9 AM.               The 17 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  38.       Begin: Sunday, August 14 at 5 AM    --->     End: Wednesday, August 17 at 1 PM.               The 67 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  39.       Begin: Saturday, August 20 at 1 PM    --->     End: Sunday, August 21 at 3 PM.               The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  40.       Begin: Sunday, August 21 at 8 PM    --->     End: Wednesday, August 24 at 9 AM.               The 14 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  41.       Begin: Friday, August 26 at 12 AM    --->     End: Monday, August 29 at 6 AM.               The 61 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  42.       Begin: Saturday, August 27 at 8 AM    --->     End: Wednesday, August 31 at 2 AM.               The 43 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  43.       Begin: Tuesday, September 06 at 2 AM    --->     End: Sunday, September 11 at 11 AM.               The 82 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  44.       Begin: Thursday, September 15 at 2 PM    --->     End: Sunday, September 18 at 7 AM.               The 18 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  45.       Begin: Tuesday, September 20 at 8 AM    --->     End: Sunday, September 25 at 4 PM.               The 114 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  46.       Begin: Wednesday, September 21 at 11 PM    --->     End: Monday, September 26 at 3 PM.               The 101 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.