Growers Claim Pistachio Trees Diseased – Nursery Maintains Problem Is A Genetic Disorder

Growers Claim Pistachio Trees Diseased – Nursery Maintains Problem Is A Genetic Disorder

Several pistachio growers in California’s San Joaquin Valley have filed lawsuits against one of the nation’s leading nurseries, alleging they were sold trees with a syndrome caused by bacterial infection. However, the president of Duarte Nursery, John Duarte, disputes that claim, saying the trees have a genetic disorder.

John Duarte

John Duarte

“If you’re saying this disease causes the problem, you would have to find the symptoms of the disease in the greenhouse,” Duarte says. “You don’t want to find it, but if you did, you’d certainly find plants with disease symptoms in the greenhouses where the conditions are more conducive to the organism’s survival. What we do find is plants that are phenotypically different but that can be clearly linked to a genetic disorder in our clonal line.”

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But Rod Stiefvater, the only grower who has filed suit who was willing to talk on the record to American Fruit Grower® and Western Fruit Grower™ magazines, is convinced many of the trees he purchased from Duarte had the bacterial infection, Rhodococcus. Stiefvater, who farms more than 3,000 acres of pistachios in Fresno, Tulare, and Kern counties, says he had the trees, which exhibited what has been dubbed Pistachio Bushy Top Syndrome (PBTS) tested by university researchers.

Stiefvater, a member of the California Pistachio Research Board, says he switched to Duarte trees in 2012 because he was impressed in the past with their performance in other orchards. But the trees he planted not only grew slowly, by the spring of 2014, they were exhibiting some unusual characteristics.

“The trees flushed out, then the leaves wilted. We started seeing problems in the tops, but once we started pulling trees, we realized how bad it was,” he says. “Because we could literally pull two-year-old trees out of the ground; their root structures were just bizarre.”

Stiefvater has planted trees from other nurseries both before and after planting the trees in question, and they all had UCB-1 clonal rootstocks, the industry standard, and he says hasn’t had a problem with those. Also, he says he’s not the only one who had a problem; some industry leaders have estimated that at least 20,000–35,000 acres of pistachios planted in California and Arizona between 2011 and 2014 are at risk.

“If you look at the size of the problem, it seems extraordinarily unlikely it’s a genetic mutation because a genetic mutation doesn’t grow exponentially,” he says.

Stiefvater hopes the problem can get resolved out of court. It’s not just the $7 per tree he planted, or the cost of replanting, or even the two years of lost production.

“The bottom line is we have filed a lawsuit and resolution could take years,” he says. “As growers, we want to get trees in the ground.”