DPR Releases First Phase of State-Funded Fumigant Alternatives Study Focused on 1,3-D and Chloropicrin
SACRAMENTO – The California Department of Pesticide Regulation today released an independent scientific study on possible alternatives to a pair of widely used fumigant pesticides: 1,3-dichloropropene (1,3-D) and chloropicrin.
The fumigant 1,3-D is used in agriculture to kill soil pathogens before crops like strawberries, grapevines or trees are planted. Chloropicrin is a fumigant often paired with 1,3-D in soil fumigation. The study found that no currently available alternatives to 1,3-D and chloropicrin would work as a universal replacement for these fumigants. However, combinations of two or more alternatives could be effective for specific crops and pests. The researchers concluded that more research is needed to support effective, feasible and readily available approaches for pest management.
“These findings highlight key challenges with identifying and replacing higher risk pesticide uses with alternatives and the critical need for continued research as we work to increase access to discover more sustainable ways to manage pests,” said DPR Director Karen Morrison. “We need to test and trial safe, effective multi-factored approaches and alternative tools and methods to continue managing pests across California. It also underscores the need for DPR’s ongoing evaluation and regulatory work to protect people and our environment from risks associated with pesticide use.”
California Council on Science and Technology (CCST) conducted the study, which was reviewed by scientific experts from several universities and from non-university stakeholder groups. The first phase of research focused on the soil fumigants 1,3-D and chloropicrin. The second phase is anticipated to conclude in fall 2025 and will address, in addition to alternatives, other pre-plant soil fumigants (including dazomet, metam-sodium, metam-potassium, and methyl bromide), post-harvest commodity fumigants, and structural fumigation.
The results included 65 findings and 33 conclusions considering fumigant use and existing available alternatives. On a wide scale, CCST found currently available fumigant alternatives to 1,3-D or chloropicrin are generally less effective in pest management than conventional fumigants when individually compared. “None of these individual fumigant alternatives would qualify as drop-in replacements for fumigation, as each offers unique benefits and is constrained by unique limitations,” the study notes.
Without a drop-in, CCST researchers concluded that tailored combination approaches with alternatives are likely to yield the greatest effectiveness, versatility, and length of control, though in practice achieving consistent results for California’s crops and pests remains a challenge with combination approaches. CCST concluded more research is needed to determine which combinations would work best for each of the crops in California that are currently reliant on 1,3-D or chloropicrin.
Funded by the California Budget 2023-24, DPR commissioned the study following the release of the Sustainable Pest Management (SPM) Roadmap to look at fumigant use in the state; existing alternatives to fumigants; past and ongoing research dedicated to fumigant alternatives; the viability of adopting these alternatives to effectively manage pests in California and barriers to, and incentives for, wide-scale adoption of alternatives.
New regulations impacting the use of 1,3-D went into effect Jan. 1, 2024, and additional regulations are in development to further restrict the use of 1,3-D. Chloropicrin is currently under reevaluation at DPR. The Sustainable Pest Management (SPM) Roadmap, released in January 2023 and developed by a diverse cross-sector work group, provided a series of recommendations to streamline and accelerate systemwide efforts to identify alternatives to high-risk pesticides. The CCST study is part of multiple efforts led by DPR to achieve the objectives of the SPM Roadmap to transition to SPM as the de facto approach to pest management and phasing out the highest-risk pesticide uses by 2050.