California Chill Report: Working to Refine Chill Modeling

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Chill Modeling

Extension Specialist in Orchard Systems in the Department of Plant Science at UC Davis, Giulia Marino has been working to more thoroughly understand chill accumulation in cherry trees. The main points of focus in the research have been to try and answer two specific questions. The first aspect of the project considers the decline in fog and how that might impact chill modeling.

“Growers are wondering or worried that the model that uses simply air temperature as an input to calculate chill may not be precise,” said Marino. “They would like to integrate some new environmental parameter to be more precise in estimating the real temperature that the tree and the buds are feeling during these warm and sunny days in winter.”

The second aspect of the research seeks to potentially add more refinement to chill accumulation modeling. Marino notes that it incorporates more of a physiological approach, versus the more traditional pathological approach to chill modeling.

“In the physiological approach our hypothesis is that we don’t know, or we don’t understand fully what happens from a physiological perspective in the trees during winter,” Marino explained. “If we can find some plant-based parameter to count or to quantify chill accumulation that would make us way more precise in understanding the dormancy stage of the trees.”

Information from the UC Davis Chill Calculator shows that as of January 25, the Shafter CIMIS station has logged 52.2 portions under the dynamic model, with 958 hours below 45°F. The station in Five Points has registered 54.4 portions, with 970 hours. There have been 1,024 hours in Merced, with 56.5 cumulative portions. In Manteca, there has been 893 chill hours, equating to 55.4 portions. Finally, the CIMIS station in Durham has registered 58.6 portions, with 980 hours.

Listen to the latest chill report below.