Scientists Can’t Agree on What’s Making Pistachio Trees Sick

A new study ignites debate on the cause of pistachio bushy top syndrome, a disease that has crippled farms in California, Arizona, and New Mexico.

Written byCatherine Offord

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Standing in the orchard, Jennifer Randall could see something was seriously wrong. A plant pathologist and molecular biologist at New Mexico State University, Randall had traveled in late 2013 to Arizona to take a look at some of the state’s pistachio tree nurseries at the request of growers in the region. “I wanted them to send samples to me to test,” Randall tells The Scientist. “They said, ‘No, no, you really need to come see these trees.’”

When she arrived, “trees were actually falling down in the wind,” says Randall. “In Arizona, we have really high winds, but we’re talking three-year-old trees. That is unusual, for them to be falling down. Their root system just had not taken hold.” The trees were stunted, with peculiarly bushy tops and swollen tissue, or galls, on the stems. Growers explained that the rootstocks weren’t accepting scions—tree shoots grafted onto the ...

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Meet the Author

Catherine Offord
After undergraduate research with spiders at the University of Oxford and graduate research with ants at Princeton University, Catherine left arthropods and academia to become a science journalist. She has worked in various guises at The Scientist since 2016. As Senior Editor, she wrote articles for the online and print publications, and edited the magazine’s Notebook, Careers, and Bio Business sections. She reports on subjects ranging from cellular and molecular biology to research misconduct and science policy. Find more of her work at her website.
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