Cornell Carbohydrate Model Run: May 18, 2018 Thinning Weather Has Changed

Posted: May 18, 2018

We finished our May twilight meetings yesterday with the meeting in North East, PA. Beginning on Tuesday of this week most of our travel weather was overcast with much heavy rain.

Tuesday was the worst of the rain with a meeting in Luzerne county after severe winds and rain in Wapwallopen. We had trouble getting into the orchard that evening due to numerous downed trees. The overcast weather is reflected in the solar radiation levels at the various sites. At many orchard sites the solar radiation was in the single digits and temperatures in the upper 60’s to low 70’s. The resulting affect was the 4 day average balance predicted by the Carbohydrate model recommending decreasing the chemical thinner rate or; at best, applying your standard rate.

As mentioned during the twilight meetings this month you need to use fruit size of 10 – 12 mm diameter as a centering point; and then consider temperatures and solar radiation to develop your thinning tank mix. At the three orchard sites we visited this week, fruit size was all below 8 mm diameter. Many sites had rain and the next window of opportunity based on the weather conditions looks to begin on Sunday and run through possibly Wednesday.

Apple Carbohydrate Thinning Model Data

Contact Information

Robert Crassweller
  • Professor of Horticulture
Phone: 814-863-6163