Apple scab: primary infection period details

Weather data for Nashua NH. Forecast values begin August 13, 2009

    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 evaluated with the Jones revision of the Mills table.
    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 time and end time.
    The estimates shown below should only be used as supplements to on-site observations.
    Postinfection time limit for sterol inhibitor or strobilurin fungicides is capped at 72 hours maximum to reduce the chance of selecting for resistant strains of scab.
    Application of these fungicides up to 96 hours or more after the start of an infection
period may still provide control, but at increasing risk of resistant scab selection.

                 ******   Primary Infection Period 1 Details   ******

   Begin: Saturday, April 18 at 9 PM    --->     Last rain hour: Thursday, April 23 at 8 PM.
       Growth stage at start of period: Between Green Tip and Quarter Inch Green
       Infection period conditions rating is less than 1. This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.05 inch rain and 69 leaf wet hours, with 48 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly < 1%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, April 17, 6 AM, or if strobilurin fungicide applied since Friday, April 17, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Monday, April 20, at 10 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, April 21, at 9 PM.

       First generation lesions arising from this infection period would start appearing by Tuesday, May 5.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, May 17.

                 ******   Primary Infection Period 2 Details   ******

   Begin: Monday, April 20 at 8 PM    --->     Last rain hour: Thursday, April 23 at 7 PM.
       Growth stage at start of period: Between Green Tip and Quarter Inch Green
       Infection period conditions rating is 6. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 1.72 inch rain and 60 leaf wet hours, with 48 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 6%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Saturday, April 18, 6 AM, or if strobilurin fungicide applied since Saturday, April 18, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Wednesday, April 22, at 7 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, April 22, at 12 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, April 23, at 8 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, April 24, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Thursday, May 7.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, May 23.

     Wetting period following Thursday, April 23, 5 PM rain was too short for scab infection.
     Approximately 0.02 inch rain and 3 leaf wet hours, with 51 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 7%.

                 ******   Primary Infection Period 3 Details   ******

   Begin: Saturday, May 2 at 2 AM    --->     Last rain hour: Saturday, May 2 at 7 AM.
       Growth stage at start of period: King Bloom
       Infection period conditions rating is 3. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.03 inch rain and 11 leaf wet hours, with 55 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 9%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 27, 6 AM, or if strobilurin fungicide applied since Tuesday, April 28, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Saturday, May 2, at 10 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, May 5, at 2 AM.

       First generation lesions arising from this infection period would start appearing by Friday, May 15.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 1.

                 ******   Primary Infection Period 4 Details   ******

   Begin: Tuesday, May 5 at 12 AM    --->     Last rain hour: Thursday, May 7 at 9 PM.
       Growth stage at start of period: Full Bloom
       Infection period conditions rating is 289. This infection period accounts for roughly 54% of the year's total primary scab risk.
       Approximately 0.80 inch rain and 71 leaf wet hours, with 53 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 61%.

       Reliable protection if strobilurin fungicide was applied since Saturday, May 2, 6 AM. But over 2 inches rain during infection period caused captan or EBDC coverage depletion before end of infection period. In this case, a fungicide with post-infection activity should be used as soon as possible.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Wednesday, May 6, at 5 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 6, at 2 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 8, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 8, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Sunday, May 17.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 7.

                 ******   Primary Infection Period 5 Details   ******

   Begin: Thursday, May 7 at 1 AM    --->     Last rain hour: Saturday, May 9 at 10 AM.
       Growth stage at start of period: Between Full Bloom and Petal Fall
       Infection period conditions rating is 74. This infection period accounts for roughly 14% of the year's total primary scab risk.
       Approximately 1.28 inch rain and 45 leaf wet hours, with 58 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 75%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, May 6, 6 AM, or if strobilurin fungicide applied since Monday, May 4, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Thursday, May 7, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, May 8, at 6 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Sunday, May 10, at 1 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 10, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Tuesday, May 19.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 7.

                 ******   Primary Infection Period 6 Details   ******

   Begin: Saturday, May 9 at 2 AM    --->     Last rain hour: Saturday, May 9 at 11 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.
       Approximately 0.09 inch rain and 23 leaf wet hours, with 62 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 75%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, May 6, 6 AM, or if strobilurin fungicide applied since Monday, May 4, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Sunday, May 10, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Sunday, May 10, at 7 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, May 12, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Tuesday, May 12, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Monday, May 25.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 7.

                 ******   Primary Infection Period 7 Details   ******

   Begin: Saturday, May 9 at 7 PM    --->     Last rain hour: Saturday, May 9 at 11 PM.
       Growth stage at start of period: Between Full Bloom and Petal Fall
       Infection period conditions rating is 7. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.41 inch rain and 12 leaf wet hours, with 61 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 76%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, May 6, 6 AM, or if strobilurin fungicide applied since Monday, May 4, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Sunday, May 10, at 2 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, May 12, at 7 PM.

       First generation lesions arising from this infection period would start appearing by Monday, May 25.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 7.

                 ******   Primary Infection Period 8 Details   ******

   Begin: Thursday, May 14 at 2 PM    --->     Last rain hour: Sunday, May 17 at 10 AM.
       Growth stage at start of period: 1 - 5 days after Petal Fall
       Infection period conditions rating is 62. This infection period accounts for roughly 12% of the year's total primary scab risk.
       Approximately 0.16 inch rain and 33 leaf wet hours, with 60 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 86%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, May 11, 6 AM, or if strobilurin fungicide applied since Tuesday, May 12, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Friday, May 15, at 9 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Sunday, May 17, at 2 PM.

       First generation lesions arising from this infection period would start appearing by Saturday, May 30.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, June 11.

                 ******   Primary Infection Period 9 Details   ******

   Begin: Sunday, May 17 at 12 AM    --->     Last rain hour: Sunday, May 17 at 10 AM.
       Growth stage at start of period: Fruit Set
       Infection period conditions rating is 6. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.44 inch rain and 12 leaf wet hours, with 61 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 88%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, May 11, 6 AM, or if strobilurin fungicide applied since Tuesday, May 12, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Sunday, May 17, at 7 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, May 20, at 12 AM.

       First generation lesions arising from this infection period would start appearing by Monday, June 1.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 20.

     Wetting period following Sunday, May 24, 2 AM rain was too short for scab infection.
     Approximately 0.02 inch rain and 9 leaf wet hours, with 57 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 88%.

                 ******   Primary Infection Period 10 Details   ******

   Begin: Wednesday, May 27 at 2 AM    --->     Last rain hour: Sunday, May 31 at 8 PM.
       Growth stage at start of period: 6 or more days after Petal Fall
       Infection period conditions rating is 83. This infection period accounts for roughly 16% of the year's total primary scab risk.
       Approximately 1.28 inch rain and 88 leaf wet hours, with 53 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 100%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Sunday, May 24, 6 AM, or if strobilurin fungicide applied since Monday, May 25, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Thursday, May 28, at 12 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Thursday, May 28, at 6 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Saturday, May 30, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Saturday, May 30, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Monday, June 8.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 20.