California growers who have relied on paraquat-dichloride to burn down weeds ahead of planting now have a hard deadline to plan around: as of August 6, 2026, every company that registered a paraquat product in California has voluntarily cancelled it, according to the state Department of Pesticide Regulation. The move effectively ends new sales of one of the state’s most widely applied herbicides, following nearly two years of regulatory review into its health and environmental effects.

What happened

DPR announced the completed phase-out this month, confirming that the last remaining registrant withdrew its paraquat products from the state on Aug. 6. The exits happened in stages rather than all at once: Syngenta was first to go, voluntarily cancelling its Gramoxone SL 3.0 registration effective April 1, 2026, and other manufacturers followed over the summer.

Growers and dealers aren’t cut off immediately. Under DPR’s rules, licensed dealers can continue selling existing inventory for up to two years from each product’s individual cancellation date, meaning some paraquat products bought in California this year could legally remain on shelves into 2028. Growers who already have product on hand can keep using it as long as they follow the label and current regulations.

Why it’s happening

The withdrawals are voluntary, not a state ban, but they come as DPR has been working through a mandatory human health and environmental reevaluation of paraquat ordered by Assembly Bill 1963, which Gov. Newsom signed in 2024 to fast-track scrutiny of the chemical. DPR published preliminary findings in December 2024: the agency found paraquat could harm birds and other non-target wildlife, and identified a possible, though not yet confirmed, association between paraquat exposure and thyroid problems and birth defects. Notably, DPR’s preliminary review lined up with prior EPA findings in one respect: it did not find a causal link between paraquat and Parkinson’s disease, despite that link being central to a wave of federal lawsuits against manufacturers in recent years.

DPR Director Karen Morrison said the department intends to help growers manage the transition, pointing to the state’s Sustainable Pest Management grant program, which funds research into pesticide alternatives and has a 2027 funding cycle with applications due Sept. 1, 2026, as one resource for operations looking for a replacement weed-control strategy.

The scrutiny intensified after a high-profile incident in March 2026, when roughly 60 gallons of paraquat spilled onto a roadway in Dorris, in Siskiyou County, after a container fell from a truck. Around 600 residents, including students at a local elementary school, were ordered to shelter in place while multiple agencies responded. The Environmental Working Group, which has pushed for a nationwide paraquat ban, cited the spill as evidence the chemical poses risks beyond the field.

Who’s affected

Paraquat has been one of California’s most heavily used restricted herbicides, applied mainly as a pre-plant burndown treatment. According to an Environmental Working Group analysis of state pesticide-use data, roughly 5.3 million pounds of paraquat were applied statewide between 2017 and 2021, with about two-thirds of that use concentrated in five San Joaquin Valley counties, Kern, Kings, Fresno, Tulare and Merced. The same analysis identified J.G. Boswell Company and The Wonderful Company as the state’s two largest users in 2021, together accounting for roughly a quarter of all paraquat applied statewide; Wonderful’s use was tied largely to pistachios, almonds and pomegranates, while Boswell applied it ahead of cotton and tomatoes. The herbicide has also seen wider use ahead of corn, peanuts, soybeans and wine grapes.

That concentration means the phase-out will land hardest on Central Valley tree nut, cotton and row-crop operations that have used paraquat as a go-to burndown tool, particularly where growers have leaned on it as part of resistance-management programs alongside or in place of glyphosate.

Reaction has been a bit mixed. Linda Pinfold, Stanislaus County’s agricultural commissioner, told the outlet that “paraquat has been an important weed-management tool for many of our growers, and there’s no question that losing it will create challenges for some farming operations.” Farmworker and pesticide-reform advocates, meanwhile, argued the phase-out was overdue. Angela Garcia of Californians for Pesticide Reform said the situation “points to the failure of a pesticide regulatory framework that does not take swift action when the science and when people have been bringing up concerns over the years,” while Laura Plascencia of Valley Improvement Projects said the episode has raised broader community demands for transparency about which chemicals are used near farmworkers and neighborhoods.

What’s next

DPR’s formal reevaluation of paraquat isn’t actually finished, the scientific and regulatory review under AB 1963 is expected to continue for several more years, even though every product has now left the market voluntarily. That means the state could still issue additional findings or restrictions down the line, though with no registered products left in California, the practical effect for growers is already in motion.

For now, growers holding paraquat inventory should confirm cancellation dates with their supplier to understand their specific two-year use-up window, and should begin evaluating alternative burndown and resistance-management strategies, whether through other herbicide chemistries, mechanical cultivation, or emerging non-chemical approaches DPR is funding through its pest-management grant programs.