Computer modeling drives precision bloom thinning in apple orchards

This spring, New York apple growers are applying the results of computer modeling-based orchard management research funded by the Northern New York Agricultural Development Program (NNYADP) to more precisely manage their orchard thinning practices with a goal of producing higher quality fruit for harvest this fall. A free recorded webinar highlighting this work is available here.

In 2018, with small grant funding from the farmer-driven NNYADP, Cornell University and Cooperative Extension fruit specialists began evaluating how to best time the application of apple bloom thinning materials through use of the Network for Environment and Weather Applications (NEWA) computer modeling system at Cornell University.

In 2020, a computer application known as the Pollen Tube Growth Model is available to growers for the second year. The model considers input entered by individual growers to generate orchard application-timing graphs.

The webinar recording includes a presentation by Cornell University Assistant Professor Gregory Peck, Ph.D., on how growers can implement the model in their orchards by measuring apple blossom styles at early bloom and determining when enough bloom is open to start the model. NEWA Director Dan Olmstead offers a tutorial on how to enter orchard block, apple variety, and other grower-specific information into the model posted at

Virginia Tech developed the Pollen Tube Growth Model and conducted validation testing in orchards in Virginia, Washington, and New York State. The model can currently be applied to seven varieties of apples: Fuji, Gala, Golden Delicious, Granny Smith, Honeycrisp, Pink Lady, and Red Delicious. For growers in New York, the model uses weather data provided through the Northeast Regional Climate Center at Cornell University.

“Precision thinning early in the current growing season is critical to reducing crop load which encourages return bloom the following season in biennial varieties including Honeycrisp and Fuji. It also allows us to being the thinning process early in difficult-to-thin varieties, for example: Gala,” says Michael Basedow, a tree fruit specialist with the Cornell Cooperative Extension Eastern New York Commercial Horticulture Program.

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