In an effort to understand the impact of warmer winters on walnut trees, UC Cooperative Extension Orchard Systems Advisor, Kat Jarvis-Shean has been involved in a comprehensive multi-year trial. The study has included simulating warmer winter conditions on trees and evaluating the effectiveness of dormancy-breaking treatments on bud break timing.
Jarvis-Shean revealed that treatments like hydrogen cyanamide, marketed as Dormex, and CAN-17 showed promise in stimulating earlier bud break in walnut trees. However, the impact varied depending on orchard health and age. While younger, robust orchards saw minimal yield increases, older orchards facing decline exhibited significant improvements in yield with Dormex applications.
“What was more interesting was we worked at the Nickels Soil Lab in a block that had been declining in yield, that was tightly spaced, that had a lot of limb dieback. We definitely saw an increase in yield at four percent Dormex that was significant and a slight increase in yield also at two percent,” said Jarvis-Shean. “It was sort of settled into a lower bud break scenario and my thinking is that we got some additional bud break to sort of wake those trees out of kind of a slumber. What we’ll need to see this year is whether we can continue that increase in yield.”
Information from the UC Davis Chill Calculator shows that as of February 20, the Shafter CIMIS station has logged 55.9 portions under the dynamic model, with 770 hours below 45°F. The station in Five Points has registered 59.5 portions, with 778 hours. There have been 947 hours in Merced, with 61.3 cumulative portions. In Manteca, there have been 719 chill hours, equating to 61.9 portions. Finally, the CIMIS station in Durham has registered 67.6 portions, with 871 hours.
Listen to the segment below.