Hughson nursery deals with problem pistachio trees

Duarte Nursery sold a widely planted type of pistachio tree that has posed serious problems for growers in the San Joaquin Valley.

As many as 20,000 acres could be affected by a disorder that is known as bushy top syndrome and has resulted in stunted growth and other problems, said Robert Klein, manager of the California Pistachio Research Board in Fresno.

John Duarte, president of the family-owned company, said it has reached legal settlements with most growers and hopes to do the same with others. He declined to detail the settlement terms.

“We want to work with our growers as much as we can,” Duarte said. “We want to maintain goodwill in the industry.”

Klein said the syndrome, new to the pistachio industry, involves trees planted in 2011 or later. Orchards typically need six years before producing a crop, he said, so current nut supplies are not affected.

The 20,000 acres nonetheless are a large investment for the industry, which has boomed from 1,700 bearing acres in 1977 to about 225,000 today, mostly from Merced to Kern counties.

Kings County grower Chuck Nichols told the Visalia Times-Delta last month that bushy top has been “a big can of worms.” He said he has pulled 75 of his 300 affected acres and has contacted other growers about possibly suing the nursery.

Research done for the board concluded that the cause is Rhodococcus fascians bacteria, which are known to infect some ornamental plants. Duarte disagrees. He said testing at the nursery has not found the microbe, and a more likely cause is a mutation in the genes that make up this pistachio type.

The nursery uses cloning to propagate its trees in a laboratory, and it bills itself as a source of “clean” plants.

Duarte is the top producer of pistachio trees for California growers and a key part of Stanislaus County’s nursery industry. It employs 1,000 people during peak production at its headquarters just west of Hughson, and about a third of that year-round.

John Duarte said the issue has been “disruptive” to pistachio production, which has made up about a fifth of the company’s $50 million or so in annual income, but it will survive. Pistachio sales are on hold while the problem is addressed, but the nursery also does big business in grapes, almonds, walnuts, cherries, citrus, avocados and other products.

Pistachios brought $1.03 billion in gross income to the state’s farmers in 2013, according to the California Department of Food and Agriculture. Arizona and New Mexico are the only other U.S. producers, on a scale far smaller than the Valley.

The pistachio type at issue is known as UCB-1, propagated from rootstock established in 1960 at the University of California, Berkeley. Duarte said the nursery has used it since 2000 because of advantages that include tolerance of salty water and low temperatures.

“It’s been a very successful product for us,” he said. “It’s become an industry standard for pistachio growers.”

The bushy top name was recently coined to describe the disorder. Symptoms can include discolored leaves, unstable roots and too-close spacing of the buds that develop into limbs, said Jennifer Randall, a researcher at New Mexico State University, in a recent report.

Randall said testing of young trees in a greenhouse has determined that the bacteria is the cause. She recommends that growers sanitize hand tools used for pruning and grafting.

“Although it is unclear at the moment if Rhodococcus can be mechanically transmitted in a field setting, common sense dictates extra caution while the details of this new disease are elucidated,” Randall wrote.

Although she was able to test for the bacteria in a lab, researchers have not developed a means for testing large numbers of trees in the field.

Duarte said he remains open to the idea that the bacteria are to blame, and the company has stepped up sanitation in any case. He said herbicide damage and nutritional deficiencies do not appear to be involved.

Duarte said that leaves mutation as a likely cause.

“From time to time, genes change in any living things,” he said. “Sometimes they change for the better, and sometimes they change for the worse.”

A bacterial cause would require removing an entire orchard, he said, but a mutation would mean replacing just the affected trees.

This story was originally published May 9, 2015 at 4:58 PM with the headline "Hughson nursery deals with problem pistachio trees."