Basic information on primary and secondary apple scab infection periods |

Background Information for this page |

Return to Apple list for Westhampton MA |

Weather data for Westhampton MA. Forecast values begin December 31, 2018 |

Each expected ascospore release is
tracked as a separate event. Infection
periods representing separate ascospore releases can overlap. Wetting period duration is compared against
the Revised MillsTable by MacHardy et al. for daytime rains during the
primary scab season to estimate 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 compared to the Jones revision of the
Mills table to estimate if wetting was long enough for infection to occur.
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 19, 5 AM rain was too short for scab infection. |

Infection period 1. Begin: Wednesday, April 25 at 2 AM ---> End: Saturday, April 28 at 3 PM. Growth stage at start of period: Between Green Tip and Quarter Inch Green Best guess is that this infection period accounts for 0.6 % of the season's total primary scab infection risk. |

Infection period 2.
Begin: Friday, April 27 at 11 AM ---> End: Sunday, April 29 at 11 PM. Growth stage at start of period: Between Half Inch Green and Tight Cluster Best guess is that this infection period accounts for 0.2 % of the season's total primary scab infection risk. |

Infection period 3. Begin: Saturday, April 28 at 11 PM ---> End: Tuesday, May 01 at 3 PM. Growth stage at start of period: Between Half Inch Green and Tight Cluster Best guess is that this infection period accounts for 0.5 % of the season's total primary scab infection risk. |

Infection period 4.
Begin: Monday, April 30 at 8 AM ---> End: Thursday, May 03 at 11 AM. 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: Thursday, May 03 at 6 PM ---> End: Saturday, May 05 at 7 AM. Growth stage at start of period: Open Cluster Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk. |

Infection period 6.
Begin: Friday, May 04 at 8 PM ---> End: Monday, May 07 at 2 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 7. Begin: Sunday, May 06 at 4 AM ---> End: Tuesday, May 08 at 2 PM. Growth stage at start of period: Between Full Pink and King Bloom Best guess is that this infection period accounts for 12 % of the season's total primary scab infection risk. |

Infection period 8.
Begin: Saturday, May 12 at 10 AM ---> End: Wednesday, May 16 at 3 PM. Growth stage at start of period: Between Full Bloom and Petal Fall Best guess is that this infection period accounts for 17 % of the season's total primary scab infection risk. |

Infection period 9. Begin: Tuesday, May 15 at 11 AM ---> End: Thursday, May 17 at 5 PM. Growth stage at start of period: Between Full Bloom and Petal Fall Best guess is that this infection period accounts for 32 % of the season's total primary scab infection risk. |

Infection period 10.
Begin: Saturday, May 19 at 9 AM ---> End: Wednesday, May 23 at 3 PM. Growth stage at start of period: 1 - 5 days after Petal Fall Best guess is that this infection period accounts for 20 % of the season's total primary scab infection risk. |

Infection period 11. Begin: Tuesday, May 22 at 12 PM ---> End: Friday, May 25 at 11 AM. Growth stage at start of period: Fruit Set Best guess is that this infection period accounts for 4 % of the season's total primary scab infection risk. |

Infection period 12.
Begin: Sunday, May 27 at 11 AM ---> End: Tuesday, May 29 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 8 % of the season's total primary scab infection risk. |

Infection period 13. Begin: Friday, June 01 at 11 AM ---> End: Wednesday, June 06 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 0.4 % of the season's total primary scab infection risk. |

Infection period 14.
Begin: Monday, June 04 at 2 AM ---> End: Thursday, June 07 at 4 PM. 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. |

Infection period 15. Begin: Wednesday, June 13 at 2 PM ---> End: Friday, June 15 at 7 PM. The 13 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 16.
Begin: Friday, June 15 at 5 AM ---> End: Saturday, June 16 at 1 PM. The 18 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 17. Begin: Monday, June 18 at 6 PM ---> End: Thursday, June 21 at 2 PM. The 22 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 18.
Begin: Saturday, June 23 at 2 AM ---> End: Monday, June 25 at 2 PM. The 49 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 19. Begin: Sunday, June 24 at 2 PM ---> End: Tuesday, June 26 at 11 AM. The 22 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 20.
Begin: Wednesday, June 27 at 5 PM ---> End: Sunday, July 01 at 10 AM. The 41 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Wetting period following July 06, 8 AM rain was too short for scab infection. |

Infection period 21.
Begin: Sunday, July 15 at 1 AM ---> End: Monday, July 16 at 3 PM. The 19 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 22. Begin: Tuesday, July 17 at 12 PM ---> End: Friday, July 20 at 1 PM. The 27 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 23.
Begin: Sunday, July 22 at 3 AM ---> End: Friday, July 27 at 3 PM. The 118 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 24. Begin: Wednesday, July 25 at 2 AM ---> End: Saturday, July 28 at 4 PM. The 74 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 25.
Begin: Friday, July 27 at 7 PM ---> End: Sunday, July 29 at 1 PM. The 25 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 26. Begin: Wednesday, August 01 at 11 AM ---> End: Sunday, August 05 at 3 PM. The 89 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 27.
Begin: Thursday, August 02 at 4 PM ---> End: Monday, August 06 at 3 PM. The 77 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 28. Begin: Tuesday, August 07 at 5 PM ---> End: Thursday, August 09 at 4 PM. The 39 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 29.
Begin: Wednesday, August 08 at 5 PM ---> End: Saturday, August 11 at 5 AM. The 30 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 30. Begin: Friday, August 10 at 2 PM ---> End: Wednesday, August 15 at 4 PM. The 106 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 31.
Begin: Saturday, August 11 at 11 AM ---> End: Thursday, August 16 at 1 PM. The 100 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 32. Begin: Friday, August 17 at 2 PM ---> End: Tuesday, August 21 at 5 PM. The 55 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 33.
Begin: Wednesday, August 22 at 3 AM ---> End: Thursday, August 23 at 11 AM. The 17 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 34. Begin: Thursday, September 06 at 2 PM ---> End: Saturday, September 08 at 2 PM. The 35 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 35.
Begin: Monday, September 10 at 8 AM ---> End: Saturday, September 15 at 5 PM. The 118 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 36. Begin: Monday, September 17 at 11 PM ---> End: Friday, September 21 at 1 PM. The 38 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 37.
Begin: Friday, September 21 at 11 PM ---> End: Sunday, September 23 at 4 PM. The 18 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 38. Begin: Tuesday, September 25 at 5 AM ---> End: Saturday, September 29 at 4 PM. The 87 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |