Farm Progress

For many California pistachio growers, this season has started out like none they’ve seen before.

Greg Northcutt, Contributing Writer

May 14, 2014

3 Min Read

For many pistachio growers, this season has started out like none they’ve seen before.

“It’s been an odd-ball year,” says PCA Zack Raven, grower services manager for Keenan Farms, Avenal, Calif.

The females trees (Kerman) bloomed earlier than the males (mostly Peters). That’s left growers wondering how that may have hurt pollination success. They won’t know until the kernels start to develop in July.

The poor synchrony between female and male trees may reflect insufficient chilling hours to release the trees completely from dormancy for normal crop development.

University of California researchers estimate that Kerman requires about 750 hours of temperatures below 45º F and Peters possibly as much as 850 chilling hours.

“The bloom was more sporadic in the younger trees,” says Raven, who works with growers throughout the San Joaquin Valley in the area Madera south to Bakersfield. “Also, the male and female trees were more in sync in the northern San Joaquin Valley, due to more chilling hours than further south.”


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“But, old-timers say not to worry. They’ve seen this before and the crop turned out okay.”

In his April Pistachio Task List newsletter, emeritus UC Cooperative Extension Farm Advisor Bob Beede notes that warm spring temperatures help overcome inadequate winter chilling. “The more rapid leafing of Kerman could be a combination of almost complete rest satisfaction and higher spring temperatures,” he says. “The fact that Peters did not respond equally to the warmer spring suggests that its chilling requirement was far less satisfied.”

At the same time, the new male cultivar, Randy, is reported to have overlapped well with Kerman this year, Beede adds.

In most of the water districts where Raven works, the continuing drought has resulted in reduced allocations of surface water to zero or near zero this year, he says. At least one of his East Side growers has no surface or ground water for his trees this season.

“Most growers south of Madera have been punching in wells this year,” Raven says. “Based on current pumping rates, they expect to have enough water for their trees. But, there’s no way to tell how long their current ground water will last.”

Many of his growers also have almond orchards. The trick for them will be to provide water when it will be most beneficial to each crop, Raven notes.  Almonds need more water and they need it sooner – in June and July – than pistachios.

For pistachios, Beede recommends growers with a limited supply of water to save as much as possible for Stage III (July through August) to promote as much kernel filling and splitting as possible.

“Irrigating at 50 percent of Etc from bud break to shell hardening was not harmful to pistachios in our regulated deficit irrigation trials,” he says.” It did result in smaller nuts, and early splits were slightly higher. However, deficit irrigating from early July to harvest has serious negative effects on kernel filling, crop weight, and split nut percentages.”

As of the first of May the 2014 pistachio crop was developing about 10 days ahead of last year’s faster-than-usual pace, Raven reports.

Assuming pollination is successful this year, he wouldn’t be surprised if production this year hits 550 million-pounds or possibly higher.

“It’s definitely an on-year,” he says. “Every field I go into has a pretty good size crop on the trees. However, I see a wide variation in nut size – from very small nuts that will likely be aborted to medium size nuts and others that are huge.”


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