Share

Apple Carbohydrate Thinning Model

The Cornell Apple Carbohydrate Thinning Model is an attempt to factor in the interaction of environmental conditions and a tree’s physiological status for precision crop load management.

Weather conditions affect an apple tree’s response to chemical thinners.  The model utilizes temperature, solar radiation and day length based upon site-specific ground based measurements from a weather station in a grower's orchard block.

To adapt models for your own orchard:

  1. On the Cornell NEWA website, go to Apple Carbohydrate Thinning (found on their drop-down menu under Crop Management)
  2. Click on the leaf on the map closest to your site
  3. Click continue
  4. Enter your Green Tip Date and Full Bloom Date then hit the green Calculate button

Special Notes for Tables

  1. The 4 Day Average Balance values are derived from the current day Balance and the next 3 days to account for how the trees may respond based on predicted weather.
  2. The model is only as good as the predicted weather forecast. If the weather changes dramatically from the forecast recheck the model.
  3. Bud break and bloom dates are from grower evaluations of their orchards.

Table 1. Decision rules for using the output of the Carbohydrate model to adjust chemical thinning rate

4-day Avg. Carb. BalanceThinning RecommendationLevel Rating
> 0g/day Increase Chemical Thinner Rate by 30% None
0g/day to -20g/day Apply Standard Chemical Thinner Rate Normal
-20g/day to -40g/day Decrease Chemical Thinner Rate by 15% Low deficit
-40g/day to -60 g/day Decrease Chemical Thinner Rate by 30% Moderate deficit
-60g/day to -80 g/day Decrease Chemical Thinner Rate by 50% High deficit
< than -80g/day Do not thin (many fruits will fall off naturally) Very high deficit

Apple Carbohydrate Thinning Models for Pennsylvania Counties

 

Apple Carbohydrate Thinning Model for Biglerville, Piney Mtn, and York Springs.

Apple Carbohydrate Thinning Model for Pittsburgh Airport.

Apple Carbohydrate Thinning Model for Bedford County

Apple Carbohydrate Thinning Model for the Reading Airport.

Apple Carbohydrate Thinning Model for Cabot, Butler County

Apple Carbohydrate Thinning Model for Rock Springs.

Apple Carbohydrate Thinning Model for Lake City

Apple Carbohydrate Thinning Model for Scott Township.

Apple Carbohydrate Thinning Model for Hegins.