Basic information on primary and secondary apple scab infection periods

Background Information for this page

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Weather data for Middletown 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: Wednesday, April 13 at 12 AM    --->     End: Saturday, April 16 at 11 AM.        Growth stage at start of period:  50% Green Tip       Best guess is that this infection period accounts for 0.1 % of the season's total primary scab infection risk.

Infection period  2.       Begin: Saturday, April 16 at 7 PM    --->     End: Monday, April 18 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 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 12 PM.        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  4.       Begin: Tuesday, April 19 at 5 PM    --->     End: Sunday, April 24 at 5 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  5.       Begin: Saturday, April 23 at 8 AM    --->     End: Monday, April 25 at 3 PM.        Growth stage at start of period:  Between Quarter Inch Green and Half Inch Green       Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk.

Infection period  6.       Begin: Sunday, April 24 at 8 PM    --->     End: Friday, April 29 at 1 PM.        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  7.       Begin: Wednesday, April 27 at 2 AM    --->     End: Sunday, May 01 at 11 AM.        Growth stage at start of period:  early Tight Cluster       Best guess is that this infection period accounts for 6 % of the season's total primary scab infection risk.

Infection period  8.       Begin: Wednesday, May 04 at 2 PM    --->     End: Thursday, May 05 at 9 PM.        Growth stage at start of period:  Between Open Cluster and Full Pink       Best guess is that this infection period accounts for 14 % of the season's total primary scab infection risk.

Infection period  9.       Begin: Monday, May 09 at 11 PM    --->     End: Wednesday, May 11 at 6 PM.        Growth stage at start of period:  Between Full Pink and King Bloom       Best guess is that this infection period accounts for 1 % of the season's total primary scab infection risk.

Infection period  10.       Begin: Tuesday, May 10 at 9 PM    --->     End: Friday, May 13 at 2 PM.        Growth stage at start of period:  King Bloom       Best guess is that this infection period accounts for 0.8 % of the season's total primary scab infection risk.

Infection period  11.       Begin: Saturday, May 14 at 8 PM    --->     End: Sunday, May 22 at 7 PM.        Growth stage at start of period:  Between King Bloom and Full Bloom       Best guess is that this infection period accounts for 69 % of the season's total primary scab infection risk.

Infection period  12.       Begin: Monday, May 23 at 5 PM    --->     End: Friday, May 27 at 5 PM.        Growth stage at start of period:  95% Petal Fall       Best guess is that this infection period accounts for 0.3 % of the season's total primary scab infection risk.

Infection period  13.       Begin: Wednesday, June 01 at 8 AM    --->     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 1 % of the season's total primary scab infection risk.

Infection period  14.       Begin: Sunday, June 05 at 9 PM    --->     End: Tuesday, June 07 at 12 PM.        Growth stage at start of period:  6 or more days after Petal Fall       Best guess is that this infection period accounts for 0.3 % of the season's total primary scab infection risk.

Infection period  15.       Begin: Wednesday, June 08 at 11 PM    --->     End: Friday, June 10 at 2 PM.        Growth stage at start of period:  6 or more days after Petal Fall       Best guess is that this infection period accounts for 0.3 % of the season's total primary scab infection risk.

Infection period  16.       Begin: Thursday, June 09 at 6 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 6 % of the season's total primary scab infection risk.

Infection period  17.       Begin: Saturday, June 11 at 5 AM    --->     End: Tuesday, June 14 at 6 PM.               The 77 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  18.       Begin: Tuesday, June 14 at 5 AM    --->     End: Thursday, June 16 at 8 AM.               The 16 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  19.       Begin: Friday, June 17 at 8 AM    --->     End: Sunday, June 19 at 10 AM.               The 32 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  20.       Begin: Wednesday, June 22 at 10 AM    --->     End: Monday, June 27 at 1 PM.               The 115 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  21.       Begin: Saturday, June 25 at 11 PM    --->     End: Tuesday, June 28 at 2 PM.               The 46 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  22.       Begin: Wednesday, June 29 at 4 AM    --->     End: Friday, July 01 at 12 PM.               The 9 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  23.       Begin: Sunday, July 03 at 4 PM    --->     End: Tuesday, July 05 at 1 PM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  24.       Begin: Friday, July 08 at 6 AM    --->     End: Monday, July 11 at 4 PM.               The 40 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  25.       Begin: Tuesday, July 12 at 2 AM    --->     End: Thursday, July 14 at 1 PM.               The 26 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  26.       Begin: Wednesday, July 13 at 6 PM    --->     End: Saturday, July 16 at 2 PM.               The 29 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  27.       Begin: Monday, July 18 at 5 PM    --->     End: Wednesday, July 20 at 2 PM.               The 32 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  28.       Begin: Saturday, July 23 at 11 AM    --->     End: Sunday, July 24 at 2 PM.               The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  29.       Begin: Sunday, July 24 at 7 AM    --->     End: Monday, July 25 at 4 PM.               The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  30.       Begin: Monday, July 25 at 2 AM    --->     End: Tuesday, July 26 at 4 PM.               Next infection period starts on same day, see next infection period for combined ratings.

Infection period  31.       Begin: Monday, July 25 at 5 PM    --->     End: Wednesday, July 27 at 12 PM.               The 66 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  32.       Begin: Tuesday, July 26 at 6 PM    --->     End: Thursday, July 28 at 9 AM.               The 20 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  33.       Begin: Tuesday, August 02 at 8 PM    --->     End: Thursday, August 04 at 1 PM.               The 22 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  34.       Begin: Saturday, August 06 at 11 PM    --->     End: Tuesday, August 09 at 4 PM.               The 57 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  35.       Begin: Monday, August 08 at 5 PM    --->     End: Wednesday, August 10 at 3 PM.               The 36 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  36.       Begin: Tuesday, August 09 at 8 PM    --->     End: Thursday, August 11 at 1 PM.               The 27 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  37.       Begin: Sunday, August 14 at 5 AM    --->     End: Wednesday, August 17 at 1 PM.               The 69 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  38.       Begin: Sunday, August 21 at 10 PM    --->     End: Wednesday, August 24 at 11 AM.               The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  39.       Begin: Friday, August 26 at 2 AM    --->     End: Monday, August 29 at 6 AM.               The 63 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  40.       Begin: Saturday, August 27 at 8 AM    --->     End: Wednesday, August 31 at 1 PM.               The 52 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  41.       Begin: Tuesday, September 06 at 2 AM    --->     End: Saturday, September 10 at 1 PM.               The 97 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  42.       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  43.       Begin: Tuesday, September 20 at 11 AM    --->     End: Sunday, September 25 at 5 PM.               The 117 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  44.       Begin: Wednesday, September 21 at 11 PM    --->     End: Monday, September 26 at 5 PM.               The 107 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.