MENDOCINO CO., 8/31/26 — Six machines work after dark, moving through 200 acres of organic vineyard outside Hopland. Nobody sits on them.
They’re electric and weigh about 900 pounds each — roughly a tenth as much as a tractor and spray rig. Instead of a tank, they carry banks of UV-C lamps that damage the DNA of powdery mildew and botrytis on the vine canopy. No sulfur, no sprays.
Bonterra Organic Estates announced the pilot program in April, using six Thorvald units from Saga Robotics across its Hopland estate blocks. The same platform worked Castoro Cellars’ Central Coast vineyards for three seasons. In May, that operation expanded to more than 600 organic acres.
Nobody rides the machines, but somebody runs them.
As Mendocino County Agricultural Commissioner Angela Godwin said, “they’re designed to run without a driver,” but that’s not the same as running alone. Today, a person in the field controls the equipment.
That distinction is the regulatory fight.
One sentence in California’s workplace safety code says all self-propelled equipment, when moving under its own power, must “have an operator stationed at the vehicular controls.”
The rule allows some distance between the operator and the driver’s seat. An operator can be “occupying or being stationed at a location on the vehicle other than the normal driving position or cab” if that operator is controlling the machine.
The operator must be able to see its path and anyone nearby, remain within 10 feet of the controls and be able to reach them easily. The machine can’t exceed 2 mph, and the operator must be close enough to stop the machine.
There is no exception for fully autonomous operation. Growers have been trying to get one since 2019.
“Larger driverless tractors operating around people are the issue the [state’s Occupational Safety and Health Standards Board] process is aimed at addressing,” Godwin said in response to emailed questions.
Her understanding of Cal/OSHA’s current interpretation is that the code bars fully driverless operation when employees are in the work area.
An empty field is different. With no employees present, it isn’t a “place of employment” under Cal/OSHA’s jurisdiction. Godwin said nighttime vineyard work like Thorvald’s is consistent with that empty-field scenario.
Cal/OSHA hasn’t confirmed that reading.
Godwin also drew a distinction the state hasn’t yet made.
Lightweight specialty robots and full-size driverless tractors “raise different safety and operational questions,” she said. “Any new rule will need to distinguish between them.”
Two petitions, both denied
OSHA’s board, a seven-member panel appointed by the governor, has rejected two attempts to change the rule.
The first came in May 2019. Cal/OSHA found a “dearth of empirical study” on autonomous-equipment safety, and the board denied it.
The second came Dec. 15, 2021, from Monarch Tractor CEO Praveen Penmetsa. He asked the board to let driver-optional tractors operate without someone at the controls “within a strict set of safety guidelines.”
The board said no again.
Rulemaking “at this juncture would be premature,” it wrote. The existing rule “is not ambiguous as currently written.”
Then the board said what it was waiting for. Staff were directed “to monitor the status of Petitioner’s temporary experimental variance and request periodic updates from Cal/OSHA on its progression.”
The state’s evidence base, by its own order, was one company’s field trial. That company has since laid off its workforce.
Zimeno, Inc., doing business as Monarch Tractor, filed state notices Nov. 19, 2025, laying off 97 workers at two Livermore addresses effective that day, according to Employment Development Department records.
But it gets more complicated from there. Michael Miiller, who represented the California Association of Winegrape Growers on the state’s autonomous agricultural equipment advisory committee, said Monarch’s collapse changed nothing, because the process required by the board wasn’t possible.
“Labor unions said they wanted data from California ag workplaces,” Miiller said. “And that data cannot be collected under existing law. So, things got to an impasse.”
The rule bars unsupervised operation. Unsupervised operation is what would produce the safety record needed to decide whether to allow it.
Who is in the room
In November 2024, the OSHA’s board ordered staff to convene an advisory committee on autonomous agricultural equipment and “make a plan for data collection.”
The committee met three times. Its last meeting was in Salinas in August 2025.
John Deere, the Association of Equipment Manufacturers, Western Growers, the California Farm Bureau, Monarch and the winegrape growers represented the industry side.
The UFW Foundation, California Rural Legal Assistance, Líderes Campesinas, MICOP, the Teamsters and UFCW represented workers.
Cal/OSHA, the Department of Pesticide Regulation, the DMV’s autonomous vehicle branch and engineers from UC Davis, UC Merced and Cal Poly were also at the table.
The UFW Foundation and CRLA Foundation, whose representatives served on the committee, did not respond to emailed questions about the impasse Miiller described.
Cal/OSHA staff have since drafted regulatory options, but that document isn’t public.
The Voice asked the board for it Aug. 26. The request was routed to the Department of Industrial Relations’ communications office, which had not responded. The Voice checked every board agenda posted from January through August 2026. None contains an autonomous-equipment item.
There has been no formal notice of rulemaking, so no public comment period has opened. The advisory committee’s page hasn’t been updated since October 2025.
The board’s next meeting is Sept. 17 in Truckee. That’s the first date anything could appear.
What it would mean here
Godwin’s office doesn’t track the machines.
It doesn’t register, permit or inspect this class of equipment, and it keeps no inventory of what’s operating in Mendocino County. The Bonterra pilot is the only deployment Godwin can identify with confidence.
Her office learns about new equipment through “relationships with producers, public announcements, extension field days, and industry conversations.”
Nobody has asked the county to weigh in on section 3441, the code that demands an operator, Godwin said. There has been no complaint, variance request or local grower or dealer asking the county to intervene.
“That standard sits with Cal/OSHA and the Occupational Safety and Health Standards Board, not with county agricultural commissioners,” she said.
Miiller said the technology can work in Mendocino County’s small, hilly and heavily organic vineyard blocks.
“From my perspective, autonomous ag equipment can absolutely be used in the Mendocino vineyards you describe,” he said.
If the rule changes, Mendocino would likely feel it first in wine grapes.
“Wine grapes are the county’s dominant high-value crop and the setting where autonomy is already being piloted,” Godwin said.
The reasons are practical: narrow rows, canopy work, night treatments, soil compaction, organic programs and labor timing. Pears and other orchard crops account for much less acreage and value.
The work most likely to change is work that still puts someone on a tractor or spray rig: disease and canopy work, mowing, under-vine operations and some spraying.
Godwin listed by email what’s at stake for the county: “labor availability, worker safety (including getting people off equipment that still causes rollover and related injuries), reduced compaction and diesel use, and residue-free disease tools that fit organic systems.”
“Those are grower and workplace issues,” she said. “The safety standard itself remains Cal/OSHA’s to write and enforce.”
What about the electricity these machines will need to charge up during the day?
Change the rules. This is safer and cleaner than an operator on a tractor dragging a spray rig.
Won’t the labor unions fight anything that removes a job for their members. Efficiency is the devil if you represent labor.