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 September 2, 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 13, 2 AM rain was too short for scab infection.

Wetting period following  April 24, 4 AM rain was too short for scab infection.

Infection period  1.       Begin: Monday, April 28 at 8 AM    --->     End: Thursday, May 01 at 12 AM.        Growth stage at start of period:  Between Open Cluster and Full Pink       Best guess is that this infection period accounts for 11 % of the season's total primary scab infection risk.

Infection period  2.       Begin: Friday, May 02 at 2 AM    --->     End: Monday, May 05 at 1 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  3.       Begin: Sunday, May 04 at 1 AM    --->     End: Tuesday, May 06 at 10 AM.        Growth stage at start of period:  Between Full Pink and King Bloom       Best guess is that this infection period accounts for 9 % of the season's total primary scab infection risk.

Infection period  4.       Begin: Thursday, May 08 at 5 AM    --->     End: Saturday, May 10 at 11 AM.        Growth stage at start of period:  Between King Bloom and Full Bloom       Best guess is that this infection period accounts for 24 % of the season's total primary scab infection risk.

Infection period  5.       Begin: Friday, May 09 at 8 AM    --->     End: Sunday, May 11 at 8 AM.        Growth stage at start of period:  Between King Bloom and Full Bloom       Best guess is that this infection period accounts for 3 % of the season's total primary scab infection risk.

Infection period  6.       Begin: Friday, May 16 at 2 PM    --->     End: Sunday, May 18 at 11 AM.        Growth stage at start of period:  Between Full Bloom and Petal Fall       Best guess is that this infection period accounts for 28 % of the season's total primary scab infection risk.

Infection period  7.       Begin: Sunday, May 18 at 5 PM    --->     End: Tuesday, May 20 at 7 AM.        Growth stage at start of period:  100% Petal Fall       Best guess is that this infection period accounts for 0.3 % of the season's total primary scab infection risk.

Infection period  8.       Begin: Tuesday, May 20 at 5 PM    --->     End: Thursday, May 22 at 10 AM.        Growth stage at start of period:  1 - 5 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  9.       Begin: Thursday, May 22 at 3 PM    --->     End: Saturday, May 24 at 6 AM.        Growth stage at start of period:  1 - 5 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  10.       Begin: Tuesday, May 27 at 5 AM    --->     End: Thursday, May 29 at 3 AM.        Growth stage at start of period:  6 or more days after Petal Fall       Best guess is that this infection period accounts for 11 % of the season's total primary scab infection risk.

Infection period  11.       Begin: Saturday, May 31 at 8 AM    --->     End: Monday, June 02 at 1 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  12.       Begin: Wednesday, June 04 at 5 AM    --->     End: Saturday, June 07 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 6 % of the season's total primary scab infection risk.

Infection period  13.       Begin: Friday, June 06 at 5 AM    --->     End: Sunday, June 08 at 12 PM.               The 31 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  14.       Begin: Sunday, June 15 at 2 AM    --->     End: Tuesday, June 17 at 2 PM.               The 43 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  15.       Begin: Monday, June 16 at 8 PM    --->     End: Wednesday, June 18 at 11 AM.               The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  16.       Begin: Wednesday, June 18 at 8 PM    --->     End: Friday, June 20 at 10 AM.               The 14 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  17.       Begin: Sunday, June 22 at 8 PM    --->     End: Thursday, June 26 at 8 AM.               The 60 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  18.       Begin: Sunday, June 29 at 12 AM    --->     End: Monday, June 30 at 4 PM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  19.       Begin: Monday, June 30 at 4 AM    --->     End: Tuesday, July 01 at 2 PM.               The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  20.       Begin: Friday, July 04 at 2 AM    --->     End: Sunday, July 06 at 4 PM.               The 46 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  21.       Begin: Saturday, July 05 at 1 AM    --->     End: Monday, July 07 at 2 PM.               The 48 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  22.       Begin: Thursday, July 10 at 1 AM    --->     End: Friday, July 11 at 8 AM.               The 7 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  23.       Begin: Monday, July 21 at 5 AM    --->     End: Tuesday, July 22 at 1 PM.               Next infection period starts on same day, see next infection period for combined ratings.

Infection period  24.       Begin: Monday, July 21 at 7 PM    --->     End: Friday, July 25 at 3 PM.               The 98 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  25.       Begin: Tuesday, July 22 at 11 PM    --->     End: Saturday, July 26 at 12 PM.               The 60 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  26.       Begin: Sunday, July 27 at 6 AM    --->     End: Tuesday, July 29 at 1 PM.               The 31 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  27.       Begin: Thursday, July 31 at 8 AM    --->     End: Friday, August 01 at 11 AM.               The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  28.       Begin: Saturday, August 02 at 2 PM    --->     End: Monday, August 04 at 11 AM.               The 21 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  29.       Begin: Wednesday, August 06 at 8 AM    --->     End: Friday, August 08 at 2 PM.               The 39 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  30.       Begin: Thursday, August 07 at 10 PM    --->     End: Saturday, August 09 at 1 PM.               The 30 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  31.       Begin: Friday, August 08 at 5 PM    --->     End: Sunday, August 10 at 10 AM.               The 17 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  32.       Begin: Monday, August 11 at 2 AM    --->     End: Thursday, August 14 at 1 PM.               The 53 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  33.       Begin: Thursday, August 14 at 4 PM    --->     End: Saturday, August 16 at 2 PM.               The 33 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  34.       Begin: Friday, August 15 at 9 PM    --->     End: Sunday, August 17 at 11 AM.               The 14 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  35.       Begin: Tuesday, August 19 at 12 PM    --->     End: Wednesday, August 20 at 10 PM.               The 10 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  36.       Begin: Saturday, August 30 at 5 AM    --->     End: Monday, September 01 at 9 AM.               The 28 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.

Infection period  37.       Begin: Saturday, September 06 at 7 AM    --->     End: Monday, September 08 at 3 PM.               The 38 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection.