Apple scab: primary infection period details

Scab Infection Period Details

Background Information for this page

Return to radar list for Belchertown MA

Weather data for Belchertown MA.  Forecast values begin May 17, 2012

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.

Wetting period following  Sunday, March 25, 5 AM rain was too short for scab infection.      Approximately 0.02 inch rain and 7 leaf wet hours, with 44 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly < 1%.

Wetting period following  Wednesday, March 28, 10 AM rain was too short for scab infection.      Approximately 0.12 inch rain and 11 leaf wet hours, with 48 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 2%.

Wetting period following  Saturday, March 31, 3 AM rain was too short for scab infection.      Approximately 0.20 inch rain and 19 leaf wet hours, with 38 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 2%.

Wetting period following  Sunday, April 01, 4 PM rain was too short for scab infection.      Approximately 0.17 inch rain and 18 leaf wet hours, with 41 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 3%.

Wetting period following  Wednesday, April 04, 5 PM rain was too short for scab infection.      Approximately 0.04 inch rain and 9 leaf wet hours, with 45 F degrees average temperature during wet hours.        Cumulative scab ascospore release by end of this wetting period is roughly 3%.

******   Primary  Infection  Period  1  Details   ******     Begin: Wednesday, April 11 at 10 PM    --->     Last rain hour: Thursday, April 12 at 7 PM.             Growth stage at start of period:  Between Tight Cluster and Open Cluster        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 0.12 inch rain and 29 leaf wet hours, with 42 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 8%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Wednesday, April 4, 6 AM, or if strobilurin fungicide applied since Friday, April 6, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Friday, April 13, at 1 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Saturday, April 14, at 10 PM.              First generation lesions arising from this infection period would start appearing by Saturday, April 28.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, May 14.

******   Primary  Infection  Period  2  Details   ******     Begin: Monday, April 16 at 12 AM    --->     Last rain hour: Monday, April 16 at 2 AM.             Growth stage at start of period:  full Pink-extended        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 0.03 inch rain and 10 leaf wet hours, with 61 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 9, 6 AM, or if strobilurin fungicide applied since Tuesday, April 10, 6 AM.

Wetting period long enough only for ascospores released at night.          Opportunity for surface fungicide kickback ends Tuesday, April 17, at 2 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Thursday, April 19, at 12 AM.              First generation lesions arising from this infection period would start appearing by Thursday, May 3.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Wednesday, May 16.

******   Primary  Infection  Period  3  Details   ******     Begin: Sunday, April 22 at 12 AM    --->     Last rain hour: Monday, April 23 at 4 PM.             Growth stage at start of period:  Full Bloom        This infection period accounts for roughly 48% of the year's total primary scab risk.               Approximately 2.50 inch rain and 47 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 protection if strobilurin fungicide was applied since Wednesday, April 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, April 23, at 11 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Monday, April 23, at 4 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Wednesday, April 25, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Wednesday, April 25, at 8 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, May 9.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Monday, May 21.

******   Primary  Infection  Period  4  Details   ******     Begin: Thursday, April 26 at 5 PM    --->     Last rain hour: Friday, April 27 at 4 AM.             Growth stage at start of period:  Between Full Bloom and Petal Fall        This infection period accounts for roughly 1% of the year's total primary scab risk.               Approximately 0.14 inch rain and 15 leaf wet hours, with 50 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 60%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Monday, April 23, 6 AM, or if strobilurin fungicide applied since Saturday, April 21, 6 AM.

Lack of daytime rain reduced the portion of mature ascospores released.          Opportunity for surface fungicide kickback ends Saturday, April 28, at 8 AM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Sunday, April 29, at 5 PM.              First generation lesions arising from this infection period would start appearing by Saturday, May 12.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Thursday, May 24.

******   Primary  Infection  Period  5  Details   ******     Begin: Tuesday, May 1 at 2 AM    --->     Last rain hour: Saturday, May 5 at 4 AM.             Growth stage at start of period:  95% Petal Fall        This infection period accounts for roughly 33% of the year's total primary scab risk.               Approximately 0.66 inch rain and 91 leaf wet hours, with 51 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 87%.               Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Thursday, April 26, 6 AM, or if strobilurin fungicide applied since Saturday, April 28, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Wednesday, May 2, at 2 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 2, at 5 PM.              Opportunity for sterol inhibitor or strobilurin kickback ends Friday, May 4, at 2 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 4, at 8 AM.              First generation lesions arising from this infection period would start appearing by Tuesday, May 15.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Saturday, May 26.

******   Primary  Infection  Period  6  Details   ******     Begin: Thursday, May 3 at 1 AM    --->     Last rain hour: Monday, May 7 at 11 AM.             Growth stage at start of period:  1 - 5 days after Petal Fall        This infection period accounts for less than 1% of the year's total primary scab risk.               Approximately 0.36 inch rain and 62 leaf wet hours, with 54 F degrees average temperature during wet hours.          Cumulative scab ascospore release by end of this wetting period is roughly 87%.        Reliable pre-infection protection during this period expected if full dose + good coverage captan or EBDC fungicide applied since Sunday, April 29, 6 AM, or if strobilurin fungicide applied since Tuesday, May 1, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Friday, May 4, at 6 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Friday, May 4, at 11 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Sunday, May 6, at 1 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Sunday, May 6, at 8 AM.              First generation lesions arising from this infection period would start appearing by Wednesday, May 16.          If conidia from 1st generation lesions spread infection, 2nd generation lesions could show as early as Friday, June 1.

******   Primary  Infection  Period  7  Details   ******     Begin: Monday, May 7 at 11 PM    --->     Last rain hour: Thursday, May 10 at 10 AM.             Growth stage at start of period:  Fruit Set        This infection period accounts for roughly 14% of the year's total primary scab risk.               Approximately 1.47 inch rain and 61 leaf wet hours, with 56 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 Friday, May 4, 6 AM, or if strobilurin fungicide applied since Saturday, May 5, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Tuesday, May 8, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Wednesday, May 9, at 5 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, May 10, at 11 PM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Friday, May 11, at 8 AM.              First generation lesions arising from this infection period would start appearing by Sunday, May 20.

******   Primary  Infection  Period  8  Details   ******     Begin: Monday, May 14 at 5 AM    --->     Last rain hour: Wednesday, May 16 at 10 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 0.06 inch rain and 55 leaf wet hours, with 62 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 Thursday, May 10, 6 AM, or if strobilurin fungicide applied since Friday, May 11, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Tuesday, May 15, at 12 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), opportunity for surface fungicide kickback ends Tuesday, May 15, at 3 AM.              Opportunity for sterol inhibitor or strobilurin kickback ends Thursday, May 17, at 5 AM.   Counting from beginning of daytime ascospore release (low inoculum blocks), kickback window ends Thursday, May 17, at 8 AM.              First generation lesions arising from this infection period would start appearing by Friday, May 25.

******   Primary  Infection  Period  9  Details   ******     Begin: Monday, May 14 at 5 PM    --->     Last rain hour: Thursday, May 17 at 4 AM.             Growth stage at start of period:  6 or more days after Petal Fall        This infection period accounts for roughly 3% of the year's total primary scab risk.               Approximately 1.02 inch rain and 58 leaf wet hours, with 61 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 Thursday, May 10, 6 AM, or if strobilurin fungicide applied since Friday, May 11, 6 AM.

This infection period accompanied by daytime rain to release ascospores.          Opportunity for surface fungicide kickback ends Tuesday, May 15, at 12 PM.              Opportunity for sterol inhibitor or strobilurin fungicide kickback ends Thursday, May 17, at 5 PM.              First generation lesions arising from this infection period would start appearing by Friday, May 25.