Apple scab: primary infection period details

Scab Infection Period Details

Weather data for Hollis NH. Forecast values begin September 12, 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.

     Wetting period following Sunday, March 25, 4 AM rain was too short for scab infection.
     Approximately 0.10 inch rain and 15 leaf wet hours, with 43 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly < 1%.

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

   Begin: Wednesday, March 28 at 10 AM    --->     Last rain hour: Thursday, March 29 at 3 AM.
       Growth stage at start of period: Between Half Inch Green and Tight Cluster
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.10 inch rain and 25 leaf wet hours, with 44 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, March 20, 12 AM, or if strobilurin fungicide applied since Tuesday, March 20, 12 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Friday, March 30, at 10 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Saturday, March 31, at 10 AM.

       First generation lesions arising from this infection period would start appearing by Friday, April 20.

     Wetting period following Sunday, April 01, 5 PM rain was too short for scab infection.
     Approximately 0.19 inch rain and 17 leaf wet hours, with 40 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly < 1%.

     Wetting period following Wednesday, April 04, 6 PM rain was too short for scab infection.
     Approximately 0.02 inch rain and 5 leaf wet hours, with 46 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: Wednesday, April 11 at 9 PM    --->     Last rain hour: Thursday, April 12 at 10 PM.
       Growth stage at start of period: Between Half Inch Green and Tight Cluster
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.29 inch rain and 34 leaf wet hours, with 42 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 2%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Tuesday, March 20, 12 AM, or if strobilurin fungicide applied since Tuesday, March 20, 12 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Friday, April 13, at 1 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, April 13, at 7 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Saturday, April 14, at 9 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, April 15, at 11 AM.

       First generation lesions arising from this infection period would start appearing by Saturday, April 28.

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

   Begin: Sunday, April 15 at 11 PM    --->     Last rain hour: Monday, April 16 at 1 AM.
       Growth stage at start of period: Between Full Pink and King Bloom
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.02 inch rain and 9 leaf wet hours, with 62 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 2%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 9, 6 AM, or if strobilurin fungicide applied since Tuesday, April 10, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Tuesday, April 17, at 2 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, April 18, at 11 PM.

       First generation lesions arising from this infection period would start appearing by Thursday, May 3.

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

   Begin: Sunday, April 22 at 2 AM    --->     Last rain hour: Monday, April 23 at 7 PM.
       Growth stage at start of period: Between Full Bloom and Petal Fall
       This infection period accounts for roughly 20% of the year's total primary scab risk.
       Approximately 2.53 inch rain and 52 leaf wet hours, with 49 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 21%.

       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 1 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Monday, April 23, at 4 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Wednesday, April 25, at 2 AM.   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 Thursday, May 10.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, May 25.

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

   Begin: Thursday, April 26 at 6 PM    --->     Last rain hour: Friday, April 27 at 5 AM.
       Growth stage at start of period: Between Full Bloom and Petal Fall
       This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.23 inch rain and 15 leaf wet hours, with 50 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 23%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 23, 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 9 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Sunday, April 29, at 6 PM.

       First generation lesions arising from this infection period would start appearing by Sunday, May 13.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, May 25.

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

   Begin: Tuesday, May 1 at 3 AM    --->     Last rain hour: Saturday, May 5 at 5 AM.
       Growth stage at start of period: 1 - 5 days after Petal Fall
       This infection period accounts for roughly 21% of the year's total primary scab risk.
       Approximately 0.77 inch rain and 96 leaf wet hours, with 50 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 43%.

       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 Wednesday, May 2, at 5 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 2, at 9 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 4, at 3 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 Wednesday, May 16.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, June 1.

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

   Begin: Thursday, May 3 at 2 AM    --->     Last rain hour: Saturday, May 5 at 5 AM.
       Growth stage at start of period: 6 or more days after Petal Fall
       This infection period accounts for roughly 2% of the year's total primary scab risk.
       Approximately 0.36 inch rain and 65 leaf wet hours, with 52 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 45%.

       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 Friday, May 4, at 8 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, May 4, at 12 PM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Sunday, May 6, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 6, at 8 AM.

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

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

   Begin: Tuesday, May 8 at 2 AM    --->     Last rain hour: Thursday, May 10 at 11 AM.
       Growth stage at start of period: 6 or more days after Petal Fall
       This infection period accounts for roughly 29% of the year's total primary scab risk.
       Approximately 1.44 inch rain and 60 leaf wet hours, with 56 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 2, 6 AM, or if strobilurin fungicide applied since Friday, May 4, 6 AM.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Wednesday, May 9, at 3 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 9, at 7 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 11, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 11, at 8 AM.

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

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

   Begin: Monday, May 14 at 8 AM    --->     Last rain hour: Thursday, May 17 at 3 AM.
       Growth stage at start of period: 6 or more days after Petal Fall
       This infection period accounts for roughly 18% of the year's total primary scab risk.
       Approximately 0.51 inch rain and 66 leaf wet hours, with 61 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 93%.

       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.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Tuesday, May 15, at 3 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Thursday, May 17, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Friday, May 25.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 10.

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

   Begin: Tuesday, May 15 at 3 PM    --->     Last rain hour: Thursday, May 17 at 3 AM.
       Growth stage at start of period: 6 or more days after Petal Fall
       This infection period accounts for roughly 4% of the year's total primary scab risk.
       Approximately 0.76 inch rain and 39 leaf wet hours, with 61 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 96%.

       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.

       This infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Wednesday, May 16, at 9 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 18, at 3 PM.

       First generation lesions arising from this infection period would start appearing by Sunday, May 27.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 10.

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

   Begin: Monday, May 21 at 7 PM    --->     Last rain hour: Wednesday, May 23 at 10 PM.
       Growth stage at start of period: 6 or more days after Petal Fall
       This infection period accounts for roughly 5% of the year's total primary scab risk.
       Approximately 0.59 inch rain and 58 leaf wet hours, with 63 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 99%.

       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 Tuesday, May 22, at 2 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 23, at 3 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, May 24, at 7 PM.   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 Saturday, June 2.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, June 14.