Apple scab: primary infection period details

Weather data for Sanford ME. Forecast values begin October 17, 2008

    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: Sunday, April 27 at 8 AM    --->     Last rain hour: Tuesday, June 24 at 6 PM.
       Growth stage at start of period: early Tight Clus.
       Infection period conditions rating is 2. This infection period accounts for less than 1% of the year's total primary scab risk.
       Approximately 0.65 inch rain and 67 leaf wet hours, with 45 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 1%.

       Reliable protection if strobilurin fungicide was applied since Thursday, April 24, 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 Monday, April 28, at 11 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, April 30, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Tuesday, May 13.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 29.

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

   Begin: Monday, April 28 at 8 AM    --->     Last rain hour: Tuesday, April 29 at 10 PM.
       Growth stage at start of period: Between Half Inch Green and Tight Cluster
       Infection period conditions rating is 4. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 2.94 inch rain and 47 leaf wet hours, with 44 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 4%.

       Reliable protection if strobilurin fungicide was applied since Thursday, April 24, 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, April 30, at 12 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Thursday, May 1, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Wednesday, May 14.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 29.

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

   Begin: Saturday, May 3 at 8 AM    --->     Last rain hour: Sunday, May 4 at 3 PM.
       Growth stage at start of period: Between Half Inch Green and Tight Cluster
       Infection period conditions rating is 6. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.81 inch rain and 51 leaf wet hours, with 44 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 7%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Tuesday, April 29, 6 AM, or if strobilurin fungicide applied since Monday, April 28, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Monday, May 5, at 6 AM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, May 6, at 8 AM.

       First generation lesions arising from this infection period would start appearing by Saturday, May 17.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 14.

     Wetting period following Thursday, May 08, 2 AM rain was too short for scab infection.
     Approximately 0.03 inch rain and 9 leaf wet hours, with 54 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 7%.

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

   Begin: Friday, May 16 at 8 PM    --->     Last rain hour: Saturday, May 17 at 9 AM.
       Growth stage at start of period: Between King Bloom and Full Bloom
       Infection period conditions rating is 4. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.16 inch rain and 14 leaf wet hours, with 52 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 12%.

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

       Wetting period long enough only for ascospores released at night.

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

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Monday, May 19, at 8 PM.

       First generation lesions arising from this infection period would start appearing by Thursday, May 29.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 14.

     Wetting period following Friday, May 23, 5 PM rain was too short for scab infection.
     Approximately 0.02 inch rain and 4 leaf wet hours, with 58 F degrees average temperature during wet hours.
     Cumulative scab ascospore release by end of this wetting period is roughly 20%.

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

   Begin: Saturday, May 31 at 5 AM    --->     Last rain hour: Saturday, May 31 at 7 PM.
       Growth stage at start of period: Fruit Set
       Infection period conditions rating is 425. This infection period accounts for roughly 85% of the year's total primary scab risk.
       Approximately 0.48 inch rain and 30 leaf wet hours, with 61 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 91%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Sunday, May 25, 6 AM, or if strobilurin fungicide applied since Monday, May 26, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Sunday, June 1, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Sunday, June 1, at 3 AM.

       Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, June 3, at 5 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Tuesday, June 3, at 8 AM.

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

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

   Begin: Tuesday, June 3 at 11 PM    --->     Last rain hour: Friday, June 6 at 7 PM.
       Growth stage at start of period: 6 or more days after Petal Fall
       Infection period conditions rating is 3. This infection period accounts for roughly 1% of the year's total primary scab risk.
       Approximately 0.01 inch rain and 81 leaf wet hours, with 57 F degrees average temperature during wet hours.
       Cumulative scab ascospore release by end of this wetting period is roughly 91%.

       Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Saturday, May 31, 6 AM, or if strobilurin fungicide applied since Sunday, June 1, 6 AM.

       Wetting period long enough only for ascospores released at night.

       Opportunity for surface fungicide kickback ends Wednesday, June 4, at 7 PM.

       Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, June 6, at 11 PM.

       First generation lesions arising from this infection period would start appearing by Tuesday, June 17.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 29.

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

   Begin: Wednesday, June 4 at 7 AM    --->     Last rain hour: Friday, June 6 at 7 PM.
       Growth stage at start of period: 6 or more days after Petal Fall
       Infection period conditions rating is 56. This infection period accounts for roughly 11% of the year's total primary scab risk.
       Approximately 0.81 inch rain and 77 leaf wet hours, with 57 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 Saturday, May 31, 6 AM, or if strobilurin fungicide applied since Sunday, June 1, 6 AM.

       Infection period accompanied by daytime rain to release ascospores.

       Opportunity for surface fungicide kickback ends Thursday, June 5, at 4 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Thursday, June 5, at 5 AM.

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

       First generation lesions arising from this infection period would start appearing by Wednesday, June 18.
       If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Sunday, June 29.