Cornell Carbohydrate Model Run for April 24, 2017

A few more weather stations are in full bloom. Normal rates of chemical thinners were recommended for the weekend, and decreased rates are suggested for the next 4 days.
Cornell Carbohydrate Model Run for April 24, 2017 - News

Updated: September 29, 2017

Cornell Carbohydrate Model Run for April 24, 2017

Photo: T. Baugher, Penn State

The model was run about 1:30 PM this Monday. Warm weather on Friday and then sunny conditions on Sunday caused a few more stations to come into full bloom. Across the state most stations suggested normal rates of chemical thinners during the weekend. However, beginning today the model suggests that chemical rates be decreased over the next 4 days due to predicted weather. Sunday morning at Rock Springs we had a two hour period of low temperatures at 31 degrees F. Potentially there could be some damage on the valley floor. All stations predict temperatures to be in the mid to upper 70s by Friday. Where fruit size is small, suggested materials are carbaryl and possibly NAA or NAD. Remember that based on fruit size chemical thinners are more effective beginning at 10 mm.

Apple Carbohydrate Thinning Models for Pennsylvania Counties

For more information on the carbohydrate thinning model, visit Carbohydrate Thinning Model. For more details on factors that affect plant growth regulator performance and chemical thinner rates, visit Growth Regulators in Apple and Pear Production.

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

4-day Av. Carb. BalanceThinning RecommendationLevel Rating
> 0g/dayIncrease Chemical Thinner Rate by 30%None
0g/day to -20g/dayApply Standard Chemical Thinner RateNormal
-20g/day to -40g/dayDecrease Chemical Thinner Rate by 15%Low deficit
-40g/day to -60 g/dayDecrease Chemical Thinner Rate by 30%Moderate deficit
-60g/day to -80 g/dayDecrease Chemical Thinner Rate by 50%High deficit
< than -80g/dayDo not thin (many fruits will fall off naturally)Very high deficit


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