Bloom synchronization is an important component for ensuring a strong pistachio yield. Research Director at the MARI Agricultural Research Institute, Masood Khezri said a challenge arises with the different chill requirements between Kerman and Peters varieties. There is a kind of bloom asynchrony between male and female trees, as the bloom is more advanced for female Kerman trees.
“Male trees remain partially dormant or delayed bloom, so the female trees do not receive enough pollen in the main period of flowering time and that can cause yield reduction,” said Khezri. “To meet this issue actually there are some rest-breaking agents, most recently Dormex.”
Dormex is a relatively new tool available to growers, having been registered for California pistachios two years ago. Since then, Khezri has been involved in a multi-year project evaluating the potential of Dormex applications. The data has shown that application timing, measured in chill portions (CP), is particularly important for optimizing its usage.
“The application of Dormex at CP 65, which was around February 24, significantly increased the yield. This increase was even higher in the low chill location,” Khezri explained. “From the 2022 research trial, we found out that timing is very critical for the application of Dormex.”
Information from the UC Davis Chill Calculator shows that as of January 23, the Shafter CIMIS station has logged 43.1 portions under the dynamic model, with 663 hours below 45°F. The station in Five Points has registered 44.1 portions, with 646 hours. There have been 795 hours in Merced, with 45.3 cumulative portions. In Manteca, there have been 620 chill hours, equating to 47 portions. Finally, the CIMIS station in Durham has registered 51.3 portions, with 744 hours.
Listen to the segment below.