The California tomato processing industry announced on Apr. 29 that it has adopted voluntary measures, including equipment cleaning and notification protocols, to stop the spread of branched broomrape, a parasitic weed that attaches to roots and depletes nutrients from crops.
This action aims to prevent quarantines and possible destruction of infected crops, which could have significant economic consequences for an industry valued at $1.6 billion in 2024. The tiny seeds of the weed can remain dormant in soil for decades and are easily dispersed by wind or movement across fields.
The University of California at Davis is working with industry partners, federal authorities, and state regulators to research ways to eradicate branched broomrape by developing field sanitation guidelines for harvesters and other agricultural equipment. Researchers are also evaluating herbicide treatments, weeding methods, detection strategies, and efforts to keep the weed from spreading further.
Cassandra Swett, a plant pathologist at UC Davis leading disinfection efforts for field equipment, said: “There are a thousand acres currently reported but we know from what we’ve observed it’s much more than that. There are two main goals: reduce the economic impact on growers in affected regions by allowing them to harvest while keeping it out of areas where it doesn’t yet exist.”
In 2025 nearly all growers and processors agreed to compliance measures related to cleaning and notification; these requirements may become mandatory this year according to Zach Bagley, managing director of the California Tomato Research Institute. “Overall this is seen as positive for the industry,” Bagley said. “The need for sanitation measures is not only due to biology but also regulatory factors.”
All tomato processing plants statewide have accepted either building wash stations or adopting cleaning protocols during the 2026 season as part of these preventive steps. Bagley added: “We can never guarantee one hundred percent that we won’t move seed but we can do our best… that’s where research comes in.”
Brad Hanson from UC Cooperative Extension noted changes brought by new compliance agreements: “With crop quarantine risk off the table for producers under compliance agreements we can talk about the problem openly… bringing this into light has been very helpful because over five years we’ve really been in the dark.” Neil McRoberts at UC Davis expressed optimism about addressing issues early before they affect other crops like carrots or potatoes.
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