Basic information on primary and secondary apple scab infection periods |

Background Information for this page |

Return to Apple list for Greenville RI |

Weather data for Greenville RI. Forecast values begin July 25, 2014 |

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. |

Infection period 1.
Begin: Tuesday, April 15 at 2 AM ---> End: Friday, April 18 at 9 AM. 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: Tuesday, April 22 at 8 PM ---> End: Friday, April 25 at 6 PM. Growth stage at start of period: Between Green Tip and Quarter Inch Green 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 26 at 5 AM ---> End: Tuesday, April 29 at 1 PM. Growth stage at start of period: Between Quarter Inch Green and Half Inch Green Best guess is that this infection period accounts for 0.2 % of the season's total primary scab infection risk. |

Infection period 4. Begin: Wednesday, April 30 at 2 AM ---> End: Sunday, May 04 at 9 AM. Growth stage at start of period: Tight Cluster Best guess is that this infection period accounts for 2 % of the season's total primary scab infection risk. |

Infection period 5.
Begin: Friday, May 09 at 7 AM ---> End: Saturday, May 10 at 5 PM. Growth stage at start of period: Between Full Pink and King Bloom Best guess is that this infection period accounts for 3 % of the season's total primary scab infection risk. |

Infection period 6. Begin: Saturday, May 10 at 2 AM ---> End: Sunday, May 11 at 12 PM. Growth stage at start of period: King Bloom Next infection period starts on same day, see next infection period for combined ratings. |

Infection period 7.
Begin: Saturday, May 10 at 5 PM ---> End: Tuesday, May 13 at 8 AM. Growth stage at start of period: King Bloom Best guess is that this infection period accounts for 21 % of the season's total primary scab infection risk. |

Infection period 8. Begin: Thursday, May 15 at 8 PM ---> End: Monday, May 19 at 11 AM. Growth stage at start of period: Between Full Bloom and Petal Fall Best guess is that this infection period accounts for 39 % of the season's total primary scab infection risk. |

Infection period 9.
Begin: Monday, May 19 at 10 PM ---> End: Friday, May 23 at 6 PM. Growth stage at start of period: 1 - 5 days after Petal Fall Best guess is that this infection period accounts for 0.8 % of the season's total primary scab infection risk. |

Infection period 10. Begin: Thursday, May 22 at 11 AM ---> End: Sunday, May 25 at 4 PM. Growth stage at start of period: Fruit Set Best guess is that this infection period accounts for 22 % of the season's total primary scab infection risk. |

Infection period 11.
Begin: Saturday, May 24 at 8 PM ---> End: Monday, 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 0.3 % of the season's total primary scab infection risk. |

Infection period 12. Begin: Monday, May 26 at 5 AM ---> End: Thursday, May 29 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 0.4 % of the season's total primary scab infection risk. |

Infection period 13.
Begin: Tuesday, May 27 at 8 PM ---> End: Saturday, May 31 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 0.8 % of the season's total primary scab infection risk. |

Infection period 14. Begin: Friday, May 30 at 8 PM ---> End: Monday, June 02 at 10 AM. Growth stage at start of period: 6 or more days after Petal Fall Best guess is that this infection period accounts for 0.2 % of the season's total primary scab infection risk. |

Infection period 15.
Begin: Wednesday, June 04 at 2 AM ---> End: Friday, June 06 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 less than 0.1 % of the season's total primary scab infection risk. |

Infection period 16. Begin: Thursday, June 05 at 2 AM ---> End: Sunday, June 08 at 9 AM. 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 17.
Begin: Monday, June 09 at 7 PM ---> End: Saturday, 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 18. Begin: Friday, June 13 at 2 AM ---> End: Monday, June 16 at 2 PM. The 36 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 19.
Begin: Wednesday, June 18 at 2 AM ---> End: Thursday, June 19 at 5 PM. The 15 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Wetting period following June 19, 5 AM rain was too short for scab infection. |

Infection period 20.
Begin: Thursday, June 26 at 2 AM ---> End: Saturday, June 28 at 1 PM. The 11 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 21. Begin: Thursday, July 03 at 10 PM ---> End: Monday, July 07 at 9 AM. The 35 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Wetting period following July 10, 2 AM rain was too short for scab infection. |

Infection period 22. Begin: Monday, July 14 at 2 PM ---> End: Saturday, July 19 at 2 PM. The 74 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 23.
Begin: Sunday, July 20 at 9 PM ---> End: Tuesday, July 22 at 1 PM. The 20 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 24. Begin: Wednesday, July 23 at 11 PM ---> End: Saturday, July 26 at 11 AM. The 12 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 25.
Begin: Sunday, July 27 at 6 AM ---> End: Wednesday, July 30 at 3 PM. The 62 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |

Infection period 26. Begin: Monday, July 28 at 3 AM ---> End: Thursday, July 31 at 12 PM. The 59 hours of rain and leaf wetness during this period provided conditions for conidial (secondary) scab infection. |