The start of the 2020 pistachio season has been a mixed bag. Most of the southern San Joaquin Valley had decent chill hours, but heat units for bloom were a mixed bag and then we hit the 2.5” rainstorm from 4/5-9 during early bloom instead of February where it should have been. Leaf out was uneven and many young orchards, especially, had problems with blanking along last year's shoots. The cause is still uncertain but see Craig Kallsen's (Kern County Subtropical Advisor) latest newsletter for a good discussion (http://cekern.ucanr.edu/?newsitem=84945).
This is the opening BLOG for our
- Author: Craig E. Kallsen
Some instances of significant scorch of the leaf canopy in Golden Hills orchards have come to my attention in the past two weeks. We do not understand the causes of scorch, and the most prominent cultivar demonstrating symptoms over the years has been the male cultivar Peters.
Scorch is not a disease but appears to develop, abiotically, later in the season, under hot temperatures. In my breeding work, there appears to be a strong genetic component in whether a given set of progeny will develop leaf scorch and associated early leaf defoliation.
I have also observed that with respect to Peters and other breeding selections in our trials that scorch appears more readily in some years than in others. Water stress later in...