Apple Carbohydrate Thinning Model

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

Apple Carbohydrate Thinning Models for Pennsylvania Counties