Apple scab: primary infection period details

Scab Infection Period Details

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Weather data for Greenville RI.  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 12 at 11 AM    --->     Last rain hour: Wednesday, April 13 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 1.75 inch rain and 46 leaf wet hours, with 47 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 Saturday, April 9, 6 AM, or if strobilurin fungicide applied since Sunday, April 10, 6 AM.

This infection period accompanied by daytime rain to release ascospores.     Opportunity for surface fungicide kickback ends Wednesday, April 13, at 6 PM.         Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, April 15, at 11 AM.         First generation lesions arising from this infection period would start appearing by Friday, April 29.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 19.

******   Primary  Infection  Period  2  Details   ******     Begin: Saturday, April 16 at 6 PM    --->     Last rain hour: Monday, April 18 at 1 AM.             Growth stage at start of period:  Between Quarter Inch Green and Half Inch Green        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 1.91 inch rain and 20 leaf wet hours, with 49 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 Saturday, April 16, 6 AM, or if strobilurin fungicide applied since Tuesday, April 12, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Sunday, April 17, at 7 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, April 19, at 6 PM.              First generation lesions arising from this infection period would start appearing by Monday, May 2.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 19.

******   Primary  Infection  Period  3  Details   ******     Begin: Sunday, April 17 at 11 PM    --->     Last rain hour: Wednesday, April 20 at 2 AM.             Growth stage at start of period:  Half-inch Green        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 0.01 inch rain and 45 leaf wet hours, with 45 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 Sunday, April 17, 6 AM, or if strobilurin fungicide applied since Thursday, April 14, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Tuesday, April 19, at 4 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Wednesday, April 20, at 11 PM.              First generation lesions arising from this infection period would start appearing by Tuesday, May 3.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 19.

******   Primary  Infection  Period  4  Details   ******     Begin: Tuesday, April 19 at 2 PM    --->     Last rain hour: Sunday, April 24 at 4 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 0.12 inch rain and 72 leaf wet hours, with 47 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 Sunday, April 17, 6 AM, or if strobilurin fungicide applied since Sunday, April 17, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, April 21, at 8 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Thursday, April 21, at 7 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Friday, April 22, at 2 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Saturday, April 23, at 8 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, May 4.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, May 21.

******   Primary  Infection  Period  5  Details   ******     Begin: Saturday, April 23 at 5 AM    --->     Last rain hour: Sunday, April 24 at 10 PM.             Growth stage at start of period:  Between Half Inch Green and Tight Cluster        This infection period accounts for roughly 3% of the year's total primary scab risk.               Approximately 0.65 inch rain and 41 leaf wet hours, with 51 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 10%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 18, 6 AM, or if strobilurin fungicide applied since Tuesday, April 19, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Sunday, April 24, at 11 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Sunday, April 24, at 12 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Tuesday, April 26, at 5 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Tuesday, April 26, at 8 AM.              First generation lesions arising from this infection period would start appearing by Saturday, May 7.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, May 24.

******   Primary  Infection  Period  6  Details   ******     Begin: Sunday, April 24 at 8 PM    --->     Last rain hour: Sunday, April 24 at 10 PM.             Growth stage at start of period:  early Tight Cluster        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 0.01 inch rain and 26 leaf wet hours, with 55 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 10%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 18, 6 AM, or if strobilurin fungicide applied since Tuesday, April 19, 6 AM.

Lack of daytime rain reduced the portion of mature ascospores released.          Opportunity for surface fungicide kickback ends Monday, April 25, at 5 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, April 27, at 3 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Wednesday, April 27, at 8 PM.   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 Monday, May 9.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, May 24.

******   Primary  Infection  Period  7  Details   ******     Begin: Wednesday, April 27 at 7 PM    --->     Last rain hour: Friday, April 29 at 2 AM.             Growth stage at start of period:  Open Cluster        This infection period accounts for roughly 13% of the year's total primary scab risk.               Approximately 0.63 inch rain and 38 leaf wet hours, with 61 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 30%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 25, 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 2 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, April 29, at 3 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Saturday, April 30, at 7 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 1, at 8 AM.              First generation lesions arising from this infection period would start appearing by Thursday, May 12.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 26.

******   Primary  Infection  Period  8  Details   ******     Begin: Wednesday, May 4 at 2 PM    --->     Last rain hour: Thursday, May 5 at 7 PM.             Growth stage at start of period:  Between King Bloom and Full Bloom        This infection period accounts for roughly 22% of the year's total primary scab risk.               Approximately 0.38 inch rain and 19 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 58%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Friday, April 29, 6 AM, or if strobilurin fungicide applied since Saturday, April 30, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, May 5, at 5 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Saturday, May 7, at 2 PM.              First generation lesions arising from this infection period would start appearing by Friday, May 20.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, June 1.

******   Primary  Infection  Period  9  Details   ******     Begin: Saturday, May 7 at 2 PM    --->     Last rain hour: Tuesday, May 10 at 11 AM.             Growth stage at start of period:  Between Full Bloom and Petal Fall        This infection period accounts for roughly 18% of the year's total primary scab risk.               Approximately 0.27 inch rain and 24 leaf wet hours, with 55 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 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 Sunday, May 8, at 1 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Tuesday, May 10, at 2 PM.              First generation lesions arising from this infection period would start appearing by Monday, May 23.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, June 3.

******   Primary  Infection  Period  10  Details   ******     Begin: Tuesday, May 10 at 9 AM    --->     Last rain hour: Wednesday, May 11 at 7 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 0.04 inch rain and 18 leaf wet hours, with 51 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 Thursday, May 5, 6 AM, or if strobilurin fungicide applied since Friday, May 6, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Wednesday, May 11, at 10 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 13, at 9 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, May 25.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 6.

******   Primary  Infection  Period  11  Details   ******     Begin: Tuesday, May 10 at 11 PM    --->     Last rain hour: Wednesday, May 11 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 0.04 inch rain and 14 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 74%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, May 5, 6 AM, or if strobilurin fungicide applied since Friday, May 6, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Wednesday, May 11, at 11 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Friday, May 13, at 11 PM.              First generation lesions arising from this infection period would start appearing by Wednesday, May 25.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 6.

******   Primary  Infection  Period  12  Details   ******     Begin: Saturday, May 14 at 8 PM    --->     Last rain hour: Friday, May 20 at 8 PM.             Growth stage at start of period:  100% Petal Fall        This infection period accounts for roughly 38% of the year's total primary scab risk.               Approximately 3.71 inch rain and 173 leaf wet hours, with 55 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 99%.               Reliable protection if strobilurin fungicide was applied since Sunday, May 15, 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 Sunday, May 15, at 6 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Monday, May 16, at 5 AM.              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 Friday, May 27.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Tuesday, June 14.

******   Primary  Infection  Period  13  Details   ******     Begin: Monday, May 23 at 2 AM    --->     Last rain hour: Wednesday, May 25 at 1 AM.             Growth stage at start of period:  6 or more days after Petal Fall        This infection period accounts for roughly 1% of the year's total primary scab risk.               Approximately 0.64 inch rain and 41 leaf wet hours, with 59 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 Wednesday, May 18, 6 AM, or if strobilurin fungicide applied since Thursday, May 19, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Tuesday, May 24, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Tuesday, May 24, at 4 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 Friday, June 3.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, June 20.

******   Primary  Infection  Period  14  Details   ******     Begin: Tuesday, May 24 at 11 PM    --->     Last rain hour: Wednesday, May 25 at 1 AM.             Growth stage at start of period:  6 or more days after Petal Fall        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 0.01 inch rain and 13 leaf wet hours, with 62 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 Wednesday, May 18, 6 AM, or if strobilurin fungicide applied since Thursday, May 19, 6 AM.

Lack of daytime rain reduced the portion of mature ascospores released.          Opportunity for surface fungicide kickback ends Wednesday, May 25, at 10 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, May 27, at 7 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 27, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 29, 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  16  Details   ******     Begin: Wednesday, June 1 at 5 PM    --->     Last rain hour: Thursday, June 2 at 12 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 0.59 inch rain and 15 leaf wet hours, with 66 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 28, 6 AM, or if strobilurin fungicide applied since Sunday, May 29, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Thursday, June 2, at 3 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Saturday, June 4, at 5 PM.              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 Monday, June 27.