Background Information for this page | |||||||
Return to Apple list for Westhampton MA | |||||||
Chart version of thinner sensitivity ratings | |||||||
Weather data for Westhampton MA. Forecast values begin September 18, 2018 | |||||||
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! The rating for each day accounts for conditions on that day AND the three following days, i.e. each rating is for a 4-day period starting on the listed day. The rated value for a day indicates relative efficacy of a thinner applied on that day based on weather conditions in the 96 hours following application. For evening applications, use the rating for the next calendar day. |
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Rough guess McIntosh King fruit diameter
dates: 12mm - May 26, Saturday 15mm - May 29, Tuesday 18mm - May 31, Thursday |
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Date after which fruit have exposure to 2 days of daily high temperature of at least 75 F: Monday, May 21 | |||||||
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. |
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THINNER
APPLICATION DATE Estimates assume morning application. For afternoon application use rating for next day. |
Average % CLOUD SHADING on application day and the next three days. < 20% = "sunny blue sky" > 40% = "cloudy" Cloudy weather on four days after application increases thinning. |
Average NIGHT HEAT UNITS = degrees above 50 F for 7pm--7am during four nights after application. Example: If average night time temperature is 55F, then value = 5. Values above 10 during four nights after application increases sensitivity to thinning. |
SUMMARY Influence of weather on sensitivity of fruit to thinning agents for 4 days following a morning application Ratings assume that fruit are within diameter range of susceptibility for thinning. |
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McIntosh 95% Petal Fall Thu, May 17 |
25% | 11 | Intermediate | ||||
McIntosh 100% Petal Fall, Fri, May 18 | sunny 9% | 1 | Intermediate | ||||
Sat, May 19 | 63% | 6 | Intermediate | ||||
Sun, May 20 | 61% | 7 | Intermediate | ||||
Mon, May 21 | sunny 3% | 6 | Intermediate | ||||
McIntosh Fruit Set, Tue, May 22 | 55% | 5 | Intermediate-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F | ||||
Wed, May 23 | sunny 14% | 10 | Intermediate-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F | ||||
Thu, May 24 | sunny 1% | 6 | Intermediate-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F | ||||
Fri, May 25 | sunny 5% | 17 | Increased sensitivity-- sensitivity may be less because of fruit exposure to 2+ days with high temps. > 75F | ||||
Sat, May 26 | sunny 9% | 18 | Increased sensitivity -- fruit >12mm probably less sensitive to thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Sun, May 27 | 66% | 0 | Intermediate -- fruit >12mm probably less sensitive to thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Mon, May 28 | 61% | 10 | Increased sensitivity -- fruit >12mm probably less sensitive to thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Tue, May 29 | sunny 9% | 13 | Stronger influence for Increased sensitivity -- fruit >15mm may have minimal sensitivity due to size and exposure to 2+ days with high temps. > 75F | ||||
Wed, May 30 | sunny 16% | 9 | Stronger influence for Increased sensitivity -- fruit >15mm may have minimal sensitivity due to size and exposure to 2+ days with high temps. > 75F | ||||
Thu, May 31 | 38% | 17 | Increased sensitivity -- fruit > 18mm are probably beyond predictable chemical thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Fri, June 1 | 57% | 20 | Intermediate -- fruit > 18mm are probably beyond predictable chemical thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Sat, June 2 | 27% | 14 | Intermediate -- fruit > 18mm are probably beyond predictable chemical thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Sun, June 3 | sunny 14% | 2 | Reduced sensitivity -- fruit > 18mm are probably beyond predictable chemical thinning due to size and exposure to 2+ days with high temps. > 75F | ||||
Mon, June 4 | 68% | 2 | Intermediate -- fruit > 18mm are probably beyond predictable chemical thinning due to size and exposure to 2+ days with high temps. > 75F | ||||