Apple scab: primary infection period details

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Weather data for Greenville RI.  Forecast values begin July 3, 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: Monday, April 28 at 7 AM    --->     Last rain hour: Sunday, June 1 at 12 AM.             Growth stage at start of period:  Between Open Cluster and Full Pink        Infection period conditions rating is 25.  This infection period accounts for roughly 6% of the year's total primary scab risk.               Approximately 5.06 inch rain and 42 leaf wet hours, with 50 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 Tuesday, April 29, at 10 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Tuesday, April 29, at 11 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, May 1, at 7 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Thursday, May 1, 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 Wednesday, May 28.

******   Primary  Infection  Period  2  Details   ******     Begin: Friday, May 2 at 2 AM    --->     Last rain hour: Sunday, May 4 at 1 PM.             Growth stage at start of period:  Between Full Pink and King Bloom        Infection period conditions rating is 5.  This infection period accounts for roughly 1% of the year's total primary scab risk.               Approximately 0.34 inch rain and 76 leaf wet hours, with 47 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 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 Saturday, May 3, at 4 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Saturday, May 3, at 10 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Monday, May 5, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Monday, May 5, at 8 AM.              First generation lesions arising from this infection period would start appearing by Friday, May 16.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, May 30.

******   Primary  Infection  Period  3  Details   ******     Begin: Saturday, May 3 at 8 PM    --->     Last rain hour: Sunday, May 4 at 1 PM.             Growth stage at start of period:  Between Full Pink and King Bloom        Infection period conditions rating is 14.  This infection period accounts for roughly 3% of the year's total primary scab risk.               Approximately 0.34 inch rain and 38 leaf wet hours, with 47 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 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 8 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Monday, May 5, at 2 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, May 6, at 8 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Wednesday, May 7, 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 Friday, May 30.

******   Primary  Infection  Period  4  Details   ******     Begin: Thursday, May 8 at 2 AM    --->     Last rain hour: Friday, May 9 at 10 PM.             Growth stage at start of period:  Between Full Bloom and Petal Fall        Infection period conditions rating is 63.  This infection period accounts for roughly 14% of the year's total primary scab risk.               Approximately 0.13 inch rain and 37 leaf wet hours, with 52 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 Friday, May 2, 6 AM, or if strobilurin fungicide applied since Sunday, May 4, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, May 8, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, May 9, at 7 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Sunday, May 11, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 11, at 8 AM.              First generation lesions arising from this infection period would start appearing by Friday, May 23.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 11.

******   Primary  Infection  Period  5  Details   ******     Begin: Friday, May 9 at 8 AM    --->     Last rain hour: Friday, May 9 at 10 PM.             Growth stage at start of period:  Between Full Bloom and Petal Fall        Infection period conditions rating is 39.  This infection period accounts for roughly 9% of the year's total primary scab risk.               Approximately 0.38 inch rain and 25 leaf wet hours, with 49 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 31%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, May 2, 6 AM, or if strobilurin fungicide applied since Sunday, May 4, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Saturday, May 10, at 2 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Monday, May 12, at 8 AM.              First generation lesions arising from this infection period would start appearing by Saturday, May 24.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 11.

******   Primary  Infection  Period  6  Details   ******     Begin: Friday, May 16 at 2 PM    --->     Last rain hour: Saturday, May 17 at 9 AM.             Growth stage at start of period:  1 - 5 days after Petal Fall        Infection period conditions rating is 140.  This infection period accounts for roughly 32% of the year's total primary scab risk.               Approximately 0.87 inch rain and 20 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 65%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, May 9, 6 AM, or if strobilurin fungicide applied since Sunday, May 11, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Saturday, May 17, at 5 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Monday, May 19, at 2 PM.              First generation lesions arising from this infection period would start appearing by Wednesday, May 28.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 14.

******   Primary  Infection  Period  7  Details   ******     Begin: Sunday, May 18 at 4 PM    --->     Last rain hour: Sunday, May 18 at 7 PM.             Growth stage at start of period:  Fruit Set        Infection period conditions rating is 20.  This infection period accounts for roughly 5% of the year's total primary scab risk.               Approximately 0.05 inch rain and 15 leaf wet hours, with 52 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 72%.               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 Monday, May 12, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Monday, May 19, at 4 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, May 21, at 4 PM.              First generation lesions arising from this infection period would start appearing by Friday, May 30.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 14.

******   Primary  Infection  Period  8  Details   ******     Begin: Tuesday, May 20 at 5 PM    --->     Last rain hour: Tuesday, May 20 at 11 PM.             Growth stage at start of period:  6 or more days after Petal Fall        Infection period conditions rating is 19.  This infection period accounts for roughly 4% of the year's total primary scab risk.               Approximately 0.26 inch rain and 16 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 79%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, May 12, 6 AM, or if strobilurin fungicide applied since Wednesday, May 14, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Wednesday, May 21, at 6 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 23, at 5 PM.              First generation lesions arising from this infection period would start appearing by Saturday, May 31.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 18.

Wetting period following  Thursday, May 22, 3 PM rain was too short for scab infection.      Approximately 0.03 inch rain and 7 leaf wet hours, with 53 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 80%.

******   Primary  Infection  Period  9  Details   ******     Begin: Tuesday, May 27 at 4 AM    --->     Last rain hour: Tuesday, May 27 at 9 PM.             Growth stage at start of period:  6 or more days after Petal Fall        Next infection period starts on same day, see next infection period for combined ratings.               Approximately 0.02 inch rain and 17 leaf wet hours, with 62 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 80%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Tuesday, May 20, 6 AM, or if strobilurin fungicide applied since Thursday, May 22, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Wednesday, May 28, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 28, at 8 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 30, at 4 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 30, at 8 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, June 11.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 25.

******   Primary  Infection  Period  10  Details   ******     Begin: Tuesday, May 27 at 5 PM    --->     Last rain hour: Tuesday, May 27 at 9 PM.             Growth stage at start of period:  6 or more days after Petal Fall        Infection period conditions rating is 86.  This infection period accounts for roughly 19% of the year's total primary scab risk.               Approximately 0.15 inch rain and 10 leaf wet hours, with 62 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 Tuesday, May 20, 6 AM, or if strobilurin fungicide applied since Thursday, May 22, 6 AM.

Infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Wednesday, May 28, at 2 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 30, at 5 PM.              First generation lesions arising from this infection period would start appearing by Wednesday, June 11.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 25.

******   Primary  Infection  Period  11  Details   ******     Begin: Saturday, May 31 at 5 PM    --->     Last rain hour: Sunday, June 1 at 12 AM.             Growth stage at start of period:  6 or more days after Petal Fall        Infection period conditions rating is 13.  This infection period accounts for roughly 3% of the year's total primary scab risk.               Approximately 0.21 inch rain and 17 leaf wet hours, with 63 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 98%.               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 2 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, June 3, at 5 PM.              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 Wednesday, June 25.

******   Primary  Infection  Period  12  Details   ******     Begin: Wednesday, June 4 at 5 AM    --->     Last rain hour: Friday, June 6 at 12 PM.             Growth stage at start of period:  6 or more days after Petal Fall        Infection period conditions rating is 16.  This infection period accounts for roughly 4% of the year's total primary scab risk.               Approximately 0.91 inch rain and 79 leaf wet hours, with 58 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 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Thursday, June 5, at 3 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Saturday, June 7, at 5 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.