Apple scab: primary infection period details

Scab Infection Period Details

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Weather data for Monmouth ME.  Forecast values begin September 20, 2011

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: Tuesday, April 26 at 12 AM    --->     Last rain hour: Friday, April 29 at 1 AM.         Growth stage at start of period:  50% Green Tip    This infection period accounts for less than 1% of the year's total primary scab risk.           Approximately 0.76 inch rain and 77 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%.    Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 25, 12 AM, or if strobilurin fungicide applied since Monday, April 25, 12 AM.

This infection period accompanied by daytime rain to release ascospores.     Opportunity for surface fungicide kickback ends Wednesday, April 27, at 9 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, April 27, at 1 PM.         Opportunity for sterol inhibitor or strobilurin kickback ends Friday, April 29, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, April 29, at 8 AM.         First generation lesions arising from this infection period would start appearing by Thursday, May 12.

******   Primary  Infection  Period  2  Details   ******     Begin: Wednesday, April 27 at 11 PM    --->     Last rain hour: Friday, April 29 at 10 PM.             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 0.32 inch rain and 35 leaf wet hours, with 58 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, April 26, 6 AM, or if strobilurin fungicide applied since Tuesday, April 26, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, April 28, at 7 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, April 29, at 11 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Saturday, April 30, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 1, at 2 PM.              First generation lesions arising from this infection period would start appearing by Saturday, May 14.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, May 28.

******   Primary  Infection  Period  3  Details   ******     Begin: Tuesday, May 3 at 11 PM    --->     Last rain hour: Saturday, May 7 at 6 PM.             Growth stage at start of period:  Between Half Inch Green and Tight Cluster        This infection period accounts for roughly 1% of the year's total primary scab risk.               Approximately 0.77 inch rain and 77 leaf wet hours, with 47 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 6%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Sunday, May 1, 6 AM, or if strobilurin fungicide applied since Monday, May 2, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, May 5, at 12 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Thursday, May 5, at 8 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 6, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Saturday, May 7, at 8 AM.              First generation lesions arising from this infection period would start appearing by Saturday, May 21.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 1.

******   Primary  Infection  Period  4  Details   ******     Begin: Saturday, May 7 at 3 PM    --->     Last rain hour: Tuesday, May 10 at 4 AM.             Growth stage at start of period:  early Tight Cluster        This infection period accounts for roughly 2% of the year's total primary scab risk.               Approximately 0.14 inch rain and 22 leaf wet hours, with 51 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, May 3, 6 AM, or if strobilurin fungicide applied since Wednesday, May 4, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Sunday, May 8, at 4 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, May 10, at 3 PM.              First generation lesions arising from this infection period would start appearing by Tuesday, May 24.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 7.

******   Primary  Infection  Period  5  Details   ******     Begin: Tuesday, May 10 at 8 AM    --->     Last rain hour: Tuesday, May 10 at 10 PM.             Growth stage at start of period:  Between Tight Cluster and Open Cluster        This infection period accounts for roughly 1% of the year's total primary scab risk.               Approximately 0.13 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 15%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, May 4, 6 AM, or if strobilurin fungicide applied since Thursday, May 5, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Wednesday, May 11, at 2 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 13, at 8 AM.              First generation lesions arising from this infection period would start appearing by Thursday, May 26.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 7.

******   Primary  Infection  Period  6  Details   ******     Begin: Saturday, May 14 at 8 PM    --->     Last rain hour: Tuesday, May 24 at 7 AM.             Growth stage at start of period:  Between Open Cluster and Full Pink        This infection period accounts for roughly 42% of the year's total primary scab risk.               Approximately 4.37 inch rain and 222 leaf wet hours, with 51 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 67%.               Reliable protection if strobilurin fungicide was applied since Wednesday, May 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, May 16, at 6 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Monday, May 16, at 7 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, May 17, at 8 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Wednesday, May 18, at 8 AM.              First generation lesions arising from this infection period would start appearing by Sunday, May 29.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, June 11.

******   Primary  Infection  Period  7  Details   ******     Begin: Monday, May 23 at 2 AM    --->     Last rain hour: Tuesday, May 24 at 7 AM.             Growth stage at start of period:  Between King Bloom and Full Bloom        This infection period accounts for roughly 4% of the year's total primary scab risk.               Approximately 0.38 inch rain and 45 leaf wet hours, with 53 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 70%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, May 20, 6 AM, or if strobilurin fungicide applied since Wednesday, May 18, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Tuesday, May 24, at 9 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Tuesday, May 24, at 11 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, May 26, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Thursday, May 26, at 8 AM.              First generation lesions arising from this infection period would start appearing by Saturday, June 4.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 20.

******   Primary  Infection  Period  8  Details   ******     Begin: Friday, May 27 at 1 AM    --->     Last rain hour: Friday, May 27 at 7 AM.             Growth stage at start of period:  Between Full Bloom and Petal Fall        This infection period accounts for roughly 2% of the year's total primary scab risk.               Approximately 0.18 inch rain and 51 leaf wet hours, with 60 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 71%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Saturday, May 21, 6 AM, or if strobilurin fungicide applied since Sunday, May 22, 6 AM.

Lack of daytime rain reduced the portion of mature ascospores released.          Opportunity for surface fungicide kickback ends Saturday, May 28, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Saturday, May 28, at 7 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Monday, May 30, at 1 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Monday, May 30, at 8 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, June 8.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 20.

******   Primary  Infection  Period  9  Details   ******     Begin: Monday, May 30 at 2 AM    --->     Last rain hour: Wednesday, June 1 at 9 PM.             Growth stage at start of period:  95% Petal Fall        This infection period accounts for roughly 2% of the year's total primary scab risk.               Approximately 0.32 inch rain and 29 leaf wet hours, with 67 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 27, 6 AM, or if strobilurin fungicide applied since Saturday, May 28, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Tuesday, May 31, at 4 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Thursday, June 2, at 2 AM.              First generation lesions arising from this infection period would start appearing by Sunday, June 12.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, June 23.

******   Primary  Infection  Period  10  Details   ******     Begin: Wednesday, June 1 at 8 AM    --->     Last rain hour: Wednesday, June 1 at 9 PM.             Growth stage at start of period:  1 - 5 days after Petal Fall        This infection period accounts for roughly 38% of the year's total primary scab risk.               Approximately 0.44 inch rain and 20 leaf wet hours, with 67 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 Friday, May 27, 6 AM, or if strobilurin fungicide applied since Saturday, May 28, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, June 2, at 6 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Saturday, June 4, at 8 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, June 15.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 28.