|Background Information for this page|
|Return to radar list for Belchertown MA|
|Chart version of thinner sensitivity ratings|
|Weather data for Belchertown MA. Forecast values begin May 19, 2013|
|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
12mm - May 24, Friday 15mm - May 28, Tuesday 18mm - May 31, Friday
|Date after which fruit have exposure to 2 days of daily high temperature of at least 75 F: Monday, May 20|
| 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.
% CLOUD SHADING
on application day and the next two days.
< 20% = "sunny blue sky"
> 40% = "cloudy"
Cloudy weather on 3 days after application increases thinning.
NIGHT HEAT UNITS
= 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.
Influence of weather on sensitivity of fruit to thinning agents for 3 days following a morning application
Ratings assume that fruit
are within diameter range
of susceptibility for thinning.
95% Petal Fall
Wed, May 15
|100% Petal Fall Thu, May 16||sunny 5%||8||Reduced sensitivity|
|Fri, May 17||sunny 9%||2||Reduced sensitivity|
|Sat, May 18||22%||4||Intermediate|
|Sun, May 19||58%||6||Stronger influence for Increased sensitivity|
|Fruit Set Mon, May 20||55%||13||Stronger influence for Increased sensitivity|
|Tue, May 21||77%||13||Stronger influence for Increased sensitivity-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F|
|Wed, May 22||41%||16||Increased sensitivity-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F|
|Thu, May 23||31%||16||Intermediate-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F|
|Fri, May 24||30%||7||Intermediate -- fruit >12mm probably less sensitive to thinning due to size and exposure to 2+ days with high temps. > 75F|
|Sat, May 25||sunny 16%||5||Reduced sensitivity -- fruit >12mm probably less sensitive to thinning due to size and exposure to 2+ days with high temps. > 75F|
|Sun, May 26||sunny 17%||6||Intermediate -- fruit >12mm probably less sensitive to thinning due to size and exposure to 2+ days with high temps. > 75F|