Background Information for this page
Return to Apple list for Middletown RI
Chart version of thinner sensitivity ratings
Weather data for Middletown RI.  Forecast values begin May 1, 2015
Estimated Apple Sensitivity to Chemical Thinners
     Other factors may outweigh the weather effects use for these estimates.  Other influences include: fruit diameter, fruit exposure to temperatures >=75 F, pollination, this year's cropload, last year's cropload, warm February-early April temperatures, frost and prolonged cool and cloudy weather during bloom, previous fall weather, foliage condition last summer)
     Ratings below are for the influence of weather on fruit sensitivity to chemical thinning agents.  Ratings assume fruit are less than 13mm diameter.  Dates in bottom rows are beyond 18mm diameter for most cultivars, and are intended only for late cultivars.
  Look at your fruit!  
Rough guess McIntosh King fruit diameter dates: 
12mm - May 31, Sunday         15mm - June 3, Wednesday          18mm - June 6, Saturday
Marker for End of Observations
May 1, 1AM Date after which fruit have exposure to 2 days of daily high temperature of at least 75 F:  Sunday,  May 31
     Very warm night temperatures (average > 69F = 19 heat units in table) can lead to "EXCESSIVE THINNING RISK", especially if combined with cloudy weather, or if combined with use of NAA.

Warm nights + Cloudy days  ----->  Increased sensitivity, maximum thinning.
Warm nights + Sunny days   -----> 
Intermediate senstivity, moderate thinning.
Cool nights + Cloudy days    ----->  Reduced sensitivity
Cool nights + Sunny days     -----> 
Reduced sensitivity, minimum thinning. 
Estimates assume morning application.
For afternoon application use rating for next day.
on application day and the next two days.

< 20% = "sunny blue sky" 
> 40% = "cloudy"
Cloudy weather on 3 days after application increases thinning.

= degrees above 50 F for 7pm--7am
for 3 nights after application. 
Example:  If average night time temperature is 55F, then value
= 5. 
Values above 10 for three nights after application increases sensitivity to thinning.
Constant used by Postbloom thinner Application date
95% Petal Fall
Fri, May 22   
100% Petal Fall Sat, May 23    23-May-15      
 Sun, May 24    24-May-15      
 Mon, May 25    25-May-15      
Fruit Set Tue, May 26    26-May-15      
 Wed, May 27    27-May-15      
 Thu, May 28    28-May-15      
 Fri, May 29    29-May-15      
 Sat, May 30    30-May-15      
 Sun, May 31    31-May-15      
 Mon, June 1    01-Jun-15      
 Tue, June 2    02-Jun-15      
 Wed, June 3    03-Jun-15      
 Thu, June 4    04-Jun-15      
 Fri, June 5    05-Jun-15      
 Sat, June 6    06-Jun-15      
 Sun, June 7    07-Jun-15      
 Mon, June 8    08-Jun-15      
 Tue, June 9    09-Jun-15      
 Wed, June 10    10-Jun-15      
 Thu, June 11    11-Jun-15      
 Fri, June 12    12-Jun-15      
 Sat, June 13    13-Jun-15      
 Sun, June 14    14-Jun-15      
 Mon, June 15    15-Jun-15      
 Tue, June 16    16-Jun-15      
 Wed, June 17    17-Jun-15      
 Thu, June 18    18-Jun-15      
 Fri, June 19    19-Jun-15      
 Sat, June 20    20-Jun-15      
 Sun, June 21    21-Jun-15      
 Mon, June 22    22-Jun-15      
 Tue, June 23    23-Jun-15      
 Wed, June 24    24-Jun-15      
 Thu, June 25    25-Jun-15      
 Fri, June 26    26-Jun-15