Apple scab: primary infection period details

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Weather data for Monmouth 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.

Wetting period following  Wednesday, April 23, 11 PM rain was too short for scab infection.      Approximately 0.72 inch rain and 10 leaf wet hours, with 53 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: Sunday, April 27 at 8 AM    --->     Last rain hour: Wednesday, April 30 at 1 AM.             Growth stage at start of period:  Between Half Inch Green and Tight Cluster        Infection period conditions rating is 8.  This infection period accounts for roughly 2% of the year's total primary scab risk.               Approximately 3.60 inch rain and 71 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 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 10 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 Thursday, May 15.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 3.

******   Primary  Infection  Period  2  Details   ******     Begin: Saturday, May 3 at 12 PM    --->     Last rain hour: Sunday, May 4 at 7 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 2% of the year's total primary scab risk.               Approximately 0.86 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 12%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, April 30, 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 11 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, May 6, at 12 PM.              First generation lesions arising from this infection period would start appearing by Sunday, May 18.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 3.

Wetting period following  Thursday, May 08, 2 AM rain was too short for scab infection.      Approximately 0.08 inch rain and 10 leaf wet hours, with 52 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 14%.

Wetting period following  Saturday, May 17, 4 AM rain was too short for scab infection.      Approximately 0.03 inch rain and 6 leaf wet hours, with 50 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 17%.

Wetting period following  Monday, May 19, 8 AM rain was too short for scab infection.      Approximately 0.04 inch rain and 8 leaf wet hours, with 50 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 17%.

Wetting period following  Monday, May 19, 7 PM rain was too short for scab infection.      Approximately 0.05 inch rain and 4 leaf wet hours, with 49 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 28%.

******   Primary  Infection  Period  3  Details   ******     Begin: Wednesday, May 21 at 4 PM    --->     Last rain hour: Friday, May 23 at 7 AM.             Growth stage at start of period:  Between King Bloom and Full Bloom        Infection period conditions rating is 134.  This infection period accounts for roughly 40% of the year's total primary scab risk.               Approximately 0.10 inch rain and 32 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 54%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, May 16, 6 AM, or if strobilurin fungicide applied since Saturday, May 17, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, May 22, at 8 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Saturday, May 24, at 4 PM.              First generation lesions arising from this infection period would start appearing by Tuesday, June 3.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 16.

******   Primary  Infection  Period  4  Details   ******     Begin: Thursday, May 22 at 5 PM    --->     Last rain hour: Friday, May 23 at 7 PM.             Growth stage at start of period:  Full Bloom        Infection period conditions rating is 40.  This infection period accounts for roughly 12% of the year's total primary scab risk.               Approximately 0.06 inch rain and 34 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 61%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, May 16, 6 AM, or if strobilurin fungicide applied since Saturday, May 17, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Friday, May 23, at 7 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Sunday, May 25, at 5 PM.              First generation lesions arising from this infection period would start appearing by Tuesday, June 3.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 16.

******   Primary  Infection  Period  5  Details   ******     Begin: Friday, May 23 at 2 PM    --->     Last rain hour: Friday, May 23 at 7 PM.             Growth stage at start of period:  Between Full Bloom and Petal Fall        Infection period conditions rating is 45.  This infection period accounts for roughly 13% of the year's total primary scab risk.               Approximately 0.10 inch rain and 18 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 73%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, May 16, 6 AM, or if strobilurin fungicide applied since Saturday, May 17, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Saturday, May 24, at 4 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Monday, May 26, at 2 PM.              First generation lesions arising from this infection period would start appearing by Wednesday, June 4.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 17.

Wetting period following  Tuesday, May 27, 2 PM rain was too short for scab infection.      Approximately 0.05 inch rain and 5 leaf wet hours, with 71 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 84%.

******   Primary  Infection  Period  6  Details   ******     Begin: Saturday, May 31 at 2 AM    --->     Last rain hour: Monday, June 2 at 7 AM.             Growth stage at start of period:  1 - 5 days after Petal Fall        Infection period conditions rating is 81.  This infection period accounts for roughly 24% of the year's total primary scab risk.               Approximately 0.82 inch rain and 42 leaf wet hours, with 55 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 Tuesday, May 27, 6 AM, or if strobilurin fungicide applied since Wednesday, May 28, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Sunday, June 1, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Sunday, June 1, at 7 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, June 3, at 2 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 Thursday, June 12.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 25.

******   Primary  Infection  Period  7  Details   ******     Begin: Monday, June 2 at 5 AM    --->     Last rain hour: Thursday, June 5 at 7 AM.             Growth stage at start of period:  Fruit Set        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 0.02 inch rain and 60 leaf wet hours, with 58 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 Friday, May 30, 6 AM, or if strobilurin fungicide applied since Saturday, May 31, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Tuesday, June 3, at 2 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Thursday, June 5, at 5 AM.              First generation lesions arising from this infection period would start appearing by Friday, June 13.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 25.

******   Primary  Infection  Period  8  Details   ******     Begin: Tuesday, June 3 at 12 PM    --->     End: Saturday, June 7 at 5 PM.             Growth stage at start of period:  6 or more days after Petal Fall        Infection period conditions rating is 21.  This infection period accounts for roughly 6% of the year's total primary scab risk.               Approximately 0.55 inch rain and 93 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 Wednesday, June 4, at 9 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, June 6, at 12 PM.              First generation lesions arising from this infection period would start appearing by Sunday, June 15.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, June 26.