Their spirits buoyed by a much-needed boost in chill hours, plus El Nino storms and fog, hundreds of pistachio growers gathered in Visalia, Calif. for the 2016 statewide Pistachio Day to look back at a dismal 2015 harvest and to look forward to projections that the 2016 crop could be a large one.

The pistachio crowd also heard about new varieties which could greatly extend the season and perhaps provide pollinators to better match the blooming of an industry workhorse, the Kerman, in a low-chill year.

And they heard presenters puzzle over the very definition of chill hours and models that look at it differently.

Poor winter chill last year, along with very warm and sunny days and tight water supplies, were blamed for a California crop that totaled only 270 million pounds. It was the smallest crop since 2006 when state acreage was half what it is now.

The average yield of 1,161 pounds per acre was the lowest since 1989. Yields in some orchards in Kern, Kings, and Fresno counties totaled less than 1,000 pounds an acre.

Citing an estimate for a 2016 crop of 725 million to 800-plus million pounds, California Pistachio Research Board (CPRB) Manager Bob Klein said, “A lot of bad things could happen between now and then. That could happen, but I will be surprised to see it quite that high.”

Klein was surprised by last year’s yields, saying, “I never thought I would see a year with less than 400 million pounds.”

Already, he said chill levels this winter are about 50 percent greater than last year. Precipitation is much higher with 8 inches in the Fresno area by late January, compared to a 4.5 inch average.

Klein pointed to big bounces upward that followed bad years with spikes in 2004 and 2000.

Chill hours a murky issue

The quantification of what constitutes adequate chill remains a bit murky. University of California (UC) Cooperative Extension Specialist Louise Ferguson explained that researchers are taking a closer look at the subject and two models for measurement.

One is based on the number of hours of accumulated chill below 45 degrees between Nov. 1 and Feb. 28. Another arrives at “chill portions” using a weighted approach for temperatures between 33 degrees and 55 degrees during the same period. With this model, intermittent warm temperatures reverse chill accumulation.

Tree Nut Updates

In addition to the chill challenge, Klein discussed other challenges facing the industry, including increased scrutiny for aflatoxin with 20 percent of loads tested for it last season.

Navel orangeworm control is a first step in reducing aflatoxin levels, and a new research program that would rely on sterile insect use is in the preliminary stage.

Klein said there is a need to bolster research capacity, and the CPRB has pursued adding additional faculty research positions. They include the addition of a plant physiologist at Fresno State University, an integrated pest management farm advisor and an Extension plant pathologist at the UC Kearney Ag Center, and endowed positions in tree nut genetics and plant soil water relations.

He added that a UC Fresno County farm advisor position will be refilled.

The research board continues to advise against using phosphite-containing pesticides and nutrients in light of export restrictions.

Klein said it appears growers may also need to comply with new food safety regulations, something he had hoped would not happen, given that pistachios are roasted and treated during processing.

He said water testing is likely under the new rules.

Klein and speakers urged support for the state’s breeding programs and the payment of royalties on new varieties.

“It’s important to collect data on who has what and the acreage out there,” he said.

New pistachio varieties

Following a talk by UC Kern County Farm Advisor Craig Kallsen on new pistachio varieties, Denise Meade, a senior intellectual property analyst with UC Davis Innovation Access-Technology Transfer Services, discussed the licensing program for UC patented cultivars.

She urged growers interested in trying new varieties to contact her for additional information.

Kallsen discussed efforts to introduce, from the UC breeding program, an additional male pollinizer for Kerman (B19-69, tentatively named “Famoso”); a new early-harvesting female cultivar (S-43, tentatively named “Gumdrop”) and its male pollinizer (N-48, tentatively named “Tejon”).

He said the need for a replacement or additional pollinizer for Kerman “has only recently been recognized with the advent of some very low-chill winters.”

B19-69 blooms tend to better match the bloom in Kerman than do the current pollinators Randy and Peters. The Randy pollinator tends to be well ahead of Kerman in years of moderate or low chill, and the full bloom of Peters tends to occur after or well after full bloom in Kerman.

In the low chill year of 2015, Kallsen said the male pollinizer N-48 was a densely flowered, early blooming male, and the pollen had a high germination percentage.

Key trait for S-43

The key trait for the female S-43 is a very early harvest date, 21 days before Kerman. In early harvesting areas, it could be ready as early as the first or second week of August. Kallsen said the cumulative edible yield of S-43 has been comparable to Golden Hills and Kerman in the first four years of bearing.

He added that the S-43 harvest was delayed a week or more after nut maturity because the commercial nut processors were not yet open to accept pistachios for processing.

Kallsen said there are some negatives related to the S-43, which is also called “Gumdrop.” While all pistachio nuts are somewhat sticky at harvest, S-43 is stickier.

“There are little drops of gum on the nuts,” Kallsen said.

Positives related to S-43 include that it would spread out the harvest season and reduce the peak requirement of labor, harvest machinery, and hulling facilities.

“The very early bloom suggests this cultivar may require less chilling for maximum yield,” Kallsen said.

And the early harvest suggests the cultivar will miss the bulk of the Navel orangeworm flights, reducing pesticide use and nut infestation.

Kallsen said the best fit for those wishing to produce S-43 initially would be for those growers closely associated with a nut processor that opens early enough to take the crop when it is ready.

New pistachio varieties

He said the three new varieties would be released to the pistachio industry in the “not-so-distant future,” and bud wood would be extremely limited.

But Kallsen added, “It is not difficult or expensive to become a licensed producer of UC bud wood.”

He urged growers to contact the UC Davis Technology Transfer Service to explore this.

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