Apple scab: primary infection period details

Scab Infection Period Details

Weather data for Monmouth ME. Forecast values begin May 17, 2012

    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 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: Sunday, March 25 at 8 AM    --->     Last rain hour: Thursday, March 29 at 6 AM.
   Growth stage at start of period: Between Green Tip and Quarter Inch Green
   This infection period accounts for less than 1% of the year's total primary scab risk.
   Approximately 0.21 inch rain and 70 leaf wet hours, with 35 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 Saturday, March 24, 12 AM, or if strobilurin fungicide applied since Saturday, March 24, 12 AM.

Wetting period long enough only for ascospores released at night.

Opportunity for surface fungicide kickback ends Tuesday, March 27, at 8 AM.

Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, March 28, at 8 AM.

First generation lesions arising from this infection period would start appearing by Tuesday, April 24.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, May 14.

     Wetting period following Wednesday, March 28, 2 AM rain was too short for scab infection.
     Approximately 0.31 inch rain and 44 leaf wet hours, with 34 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 1%.

     Wetting period following Sunday, April 01, 7 PM rain was too short for scab infection.
     Approximately 0.10 inch rain and 16 leaf wet hours, with 36 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 1%.

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

   Begin: Sunday, April 8 at 5 PM    --->     Last rain hour: Wednesday, April 11 at 4 PM.
       Growth stage at start of period: Between Quarter Inch Green and Half Inch Green
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.33 inch rain and 53 leaf wet hours, with 41 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 Tuesday, April 3, 6 AM, or if strobilurin fungicide applied since Thursday, April 5, 6 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Tuesday, April 10, at 4 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, April 11, at 2 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Wednesday, April 11, at 5 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Thursday, April 12, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Wednesday, April 25.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, May 14.

     Wetting period following Tuesday, April 10, 5 PM rain was too short for scab infection.
     Approximately 0.06 inch rain and 18 leaf wet hours, with 40 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 2%.

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

   Begin: Saturday, April 21 at 11 PM    --->     Last rain hour: Tuesday, April 24 at 7 AM.
       Growth stage at start of period: Between Open Cluster and Full Pink
       This infection period accounts for roughly 11% of the year's total primary scab risk.
       Approximately 3.56 inch rain and 64 leaf wet hours, with 45 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 18%.

       Reliable protection if strobilurin fungicide was applied since Wednesday, April 18, 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.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Monday, April 23, at 7 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Tuesday, April 24, at 2 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, April 24, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Wednesday, April 25, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Saturday, May 12.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, May 25.

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

   Begin: Thursday, April 26 at 8 PM    --->     Last rain hour: Friday, April 27 at 2 PM.
       Growth stage at start of period: Between Open Cluster and Full Pink
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.72 inch rain and 18 leaf wet hours, with 45 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 25%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Tuesday, April 24, 6 AM, or if strobilurin fungicide applied since Saturday, April 21, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Saturday, April 28, at 8 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Sunday, April 29, at 8 PM.

       First generation lesions arising from this infection period would start appearing by Wednesday, May 16.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 3.

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

   Begin: Tuesday, May 1 at 5 AM    --->     Last rain hour: Saturday, May 5 at 6 AM.
       Growth stage at start of period: Between Full Pink and King Bloom
       This infection period accounts for roughly 6% of the year's total primary scab risk.
       Approximately 0.45 inch rain and 95 leaf wet hours, with 45 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 33%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, April 26, 6 AM, or if strobilurin fungicide applied since Saturday, April 28, 6 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Thursday, May 3, at 5 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Thursday, May 3, at 8 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 4, at 5 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 4, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Friday, May 18.

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

   Begin: Friday, May 4 at 2 AM    --->     Last rain hour: Saturday, May 5 at 6 AM.
       Growth stage at start of period: Between Full Pink and King Bloom
       This infection period accounts for roughly 6% of the year's total primary scab risk.
       Approximately 0.54 inch rain and 37 leaf wet hours, with 48 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 40%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, April 26, 6 AM, or if strobilurin fungicide applied since Saturday, April 28, 6 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Saturday, May 5, at 1 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Saturday, May 5, at 4 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Monday, May 7, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Monday, May 7, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Sunday, May 20.

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

   Begin: Tuesday, May 8 at 8 AM    --->     Last rain hour: Friday, May 11 at 3 AM.
       Growth stage at start of period: Between King Bloom and Full Bloom
       This infection period accounts for roughly 32% of the year's total primary scab risk.
       Approximately 2.07 inch rain and 71 leaf wet hours, with 50 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 70%.

       Reliable protection if strobilurin fungicide was applied since Friday, May 4, 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.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Wednesday, May 9, at 4 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 11, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Tuesday, May 22.

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

   Begin: Sunday, May 13 at 5 PM    --->     Last rain hour: Tuesday, May 15 at 10 AM.
       Growth stage at start of period: Between Full Bloom and Petal Fall
       This infection period accounts for roughly 9% of the year's total primary scab risk.
       Approximately 0.05 inch rain and 38 leaf wet hours, with 55 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 77%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, May 9, 6 AM, or if strobilurin fungicide applied since Wednesday, May 9, 6 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Monday, May 14, at 3 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, May 16, at 5 PM.

       First generation lesions arising from this infection period would start appearing by Saturday, May 26.

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

   Begin: Monday, May 14 at 8 PM    --->     Last rain hour: Thursday, May 17 at 4 AM.
       Growth stage at start of period: 95% Petal Fall
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.33 inch rain and 54 leaf wet hours, with 56 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 77%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, May 10, 6 AM, or if strobilurin fungicide applied since Friday, May 11, 6 AM.

       Lack of daytime rain reduced the portion of mature ascospores released.

       Opportunity for surface fungicide kickback ends Tuesday, May 15, at 6 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 16, at 4 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, May 17, at 8 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 18, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Sunday, May 27.

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

   Begin: Tuesday, May 15 at 8 PM    --->     Last rain hour: Thursday, May 17 at 4 AM.
       Growth stage at start of period: 100% Petal Fall
       This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.82 inch rain and 37 leaf wet hours, with 57 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 78%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, May 10, 6 AM, or if strobilurin fungicide applied since Friday, May 11, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Wednesday, May 16, at 5 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 18, at 8 PM.

       First generation lesions arising from this infection period would start appearing by Monday, May 28.

                 ******   Primary Infection Period 11 Details   ******

   Begin: Tuesday, May 22 at 4 AM    --->     Last rain hour: Wednesday, May 23 at 9 AM.
       Growth stage at start of period: 6 or more days after Petal Fall
       This infection period accounts for roughly 32% of the year's total primary scab risk.
       Approximately 0.57 inch rain and 34 leaf wet hours, with 59 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 97%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, May 17, 6 AM, or if strobilurin fungicide applied since Friday, May 18, 6 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Wednesday, May 23, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 23, at 4 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 25, at 4 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 25, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Tuesday, June 5.