Protectant fungicide Respray Dates for Secondary Scab Suppression

Background Information for this page
Return to radar list for Middletown RI
       This table estimates fungicide intervals for suppressing spread of secondary scab if it should occur.  Use the appropriate primary scab respray guidelines instead of this table until ascospore releases are completed.  Rules used to estimate protection depletion change after fruit set and again after terminal bud set.  See Background Information page for details.
      Brown text with grey background indicates dates when 2nd generation scab lesions from the final ascospore release have had time to begin appearing.  After this date it is possible to confirm the status of primary scab control.  If successful control of primary apple scab infections has been confirmed, this table is no longer needed, and fungicide application dates can be made with the extended intervals adequate to prevent flyspeck and other summer diseases. 
      But if there are enough active scab infections present to cause an unacceptable risk of fruit scab infection, this table provides estimates for respray dates to keep scab infections from spreading.  If active lesions are found, fungicide protection is needed until those lesions exhaust their supply of spores, which takes about 4 weeks. 
       Depending on scab severity, market sensitivity, temperature, and proximity to harvest; shorter or longer fungicide intervals to suppress spread from active scab lesions may be more appropriate than the estimates shown below.
      The estimated date for 95+% scab ascsopore release at this site is May 9.   
The estimated McIntosh fruit set date for this site is May 13. 
The approximate terminal bud set date for this site is June 26.
Weather data for Middletown RI.  Forecast values begin May 21, 2012
Previous
Spray Date

Estimates assume that fungicide
was applied BEFORE rain
on spray date
Inches Rain Protection End Date against Secondary Scab
for full-dose
captan, mancozeb or other protectant fungicide
Percent primary scab potential beginning to show as
(1st generation)
&
2nd gen. lesions by protection end date
Respray Deadline
= Start date for next scab infection period after protection ends
Wed,  May  9 1.39 May 11, Fri (52%) 0% May 15, Tue
Thu,  May  10 0.82 May 17, Thu (76%) 1% May 21, Mon
Fri,  May  11 0 May 19, Sat (77%) 1% May 21, Mon
Sat,  May  12 0 May 20, Sun (77%) 1% May 21, Mon
Sun,  May  13 0 May 25, Fri (94%) 45% Too early to estimate
Mon,  May  14 0 May 26, Sat (94%) 52%  
Tue,  May  15 0.55 May 27, Sun (99%) 76%  
Wed,  May  16 1.06 May 28, Mon (100%) 76%  
Thu,  May  17 0 May 30, Wed (100%) 76%  
Fri,  May  18 0 May 30, Wed 76%  
Sat,  May  19 0 May 31, Thu 78%  
Sun,  May  20 0 June 1, Fri 94%  
Mon,  May  21 0.13 June 2, Sat 94%  
Tue,  May  22 0.10 June 3, Sun   94%  
Wed,  May  23 0 Too early 94%  
Thu,  May  24 0 Too early 94%  
Fri,  May  25 0 Too early 94%  
Sat,  May  26 0 Too early 94%  
Sun,  May  27 0 Too early 94%  
Mon,  May  28 0 Too early 94%  
Tue,  May  29          
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