The California Department of Pesticide Regulation (DPR) released the fourth and final component of a multi-part study exploring alternatives to fumigant pesticides. The last report focused on the risks and benefits of pre-plant fumigants.
The research conducted by the California Council on Science and Technology (CCST) specifically looked at methyl bromide and three pesticides known as MITC generators – dazomet, metam-sodium, and metam-potassium. Similar to the findings from CCST’s previous reports, this report found that, while alternatives exist, there is no single alternative that can be used as a 1:1 substitute for methyl bromide or MITC generators. In particular, the cost and effectiveness of alternatives remain a significant barrier for growers. More crop- and region-specific research is needed to determine the efficacy of alternatives at commercial scale.
“DPR has made a strong commitment to sustainable pest management and finding alternatives to fumigants,” said DPR Director Karen Morrison. “We will continue to prioritize actions to protect human health and the environment through research and innovation.”
Both methyl bromide and MITC generators are restricted material pesticides in California – a group of high-risk pesticides that are strictly regulated to protect public health and the environment.
Methyl bromide is a soil fumigant that has been largely phased out of use in routine agriculture under the Montreal Protocol because of its ozone-depleting properties. The U.S. EPA only allows its use in a few circumstances – primarily for quarantine and pre-shipment of commodities, imported goods, and nursery propagation to prevent the introduction and/or spread of pests across borders. MITC generators are used to protect timber from rot and to reduce the spread of soil-borne pests between crop seasons.
DPR has also created two new committees to support implementation of the SPM Roadmap.
The SPM Advisory Committee advises DPR on goals, tactics, policies, and partnerships that support the implementation of SPM statewide.
The Scientific Prioritization and Review Committee (SPARC) will provide science-based recommendations to inform DPR’s transparent, data-driven process for identifying and addressing potential risks to human health and the environment from pesticide use.
DPR is also prioritizing alternatives to fumigants in its annual pool of SPM grant funding. For example, in May, DPR awarded over $600,000 to a project to evaluate the application of different combinations of soil fumigant alternatives.
Fumigants are a cornerstone of conventional agriculture in the United States for combating soil-borne pests and diseases. However, fumigants also have significant limitations, including application requirements, buffer zone restrictions and the lack of available products for organic farmers.
The role of fumigants in agriculture
Fumigants are chemical agents applied before planting to eliminate pests, pathogens, and weeds, which protect crops and improve vigor and yields, especially in high-value crops like strawberries and tomatoes. Despite their effectiveness, most carry significant health and environmental risks, leading to strict regulations on their use, application timing, permitting, and buffer zones1,2. In some cases, these health concerns have led to complete bans on specific products, such as methyl bromide, which has been restricted in both the United States and Europe2,3.
Buffer zone restrictions
To reduce exposure risks, the Environmental Protection Agency (EPA) enforces strict buffer zones, areas where fumigant application is prohibited, near public spaces like schools and hospitals. Zone size depends on the fumigant used, application method, local environmental conditions, and distance to public spaces. While crucial for public safety and conservation efforts, buffer zones decrease usable farmland. Often, untreated buffer zones can lead to uneven pest control and reduced crop yields4. Buffer zones also add regulatory burdens, including signage and detailed management plans, increasing cost and complexity2.
Additional limitations of fumigants
Beyond buffer zone requirements, fumigants come with additional key limitations:
Cost: Fumigation is expensive, requiring investments in chemicals, labor, and regulatory compliance, which are often unaffordable for small-scale farmers.
Equipment: The application requires specialized equipment, including shank injectors, calibrated applicators, tarping systems, and enhanced personal protective equipment, which further increases total expenses.
Application Conditions: Efficacy depends on precise environmental conditions (soil temperature, soil moisture, weather) and properly calibrated equipment to ensure efficacy
Environmental Risks: Fumigants are highly volatile and can drift off-site, endangering nearby communities and ecosystems. Improper application may lead to water contamination or harm to non-target organisms.
Organic alternatives to fumigants
For organic farmers, the limitations of fumigants are even more pronounced, as organic certification prohibits the use of most synthetic fumigants. In response to these challenges, organic farmers rely on natural alternatives to manage soil-borne pests and diseases5:
Soil Solarization: Fallow fields are covered with plastic during peak heat for 4-8 weeks to trap solar energy, which can kill pathogens, pests, and weed seeds. This timeline may be challenging as the temperatures required for effective treatment coincide with peak growing seasons.
Anaerobic Soil Disinfestation (ASD)6: Organic materials like rice bran or mustard seed meal are incorporated into the soil and the soil is then saturated with water and covered with plastic to create anaerobic conditions. As oxygen is depleted, aerobic pests die and anaerobic species flourish, producing byproducts that further suppress pathogens. Once the field is cleared and prepared for planting, the reintroduction of oxygen into the soil then reduces anaerobic microbial populations, resulting in a cleaner overall soil. This process, however, can be quite expensive as it is water- and input-intensive and can be ineffective if fields are drained too early.
Crop Rotation and Cover Cropping: These practices disrupt pest life cycles and improve soil health; however, they are inadequate to knock down heavy infestations without additional inputs.
Biological Controls: Beneficial species help suppress pests via predation or competition. Their success depends on careful species selection, application timing, and environmental fit, and they work best when paired with other methods of control.
Introducing RevoCURB™, a safe-to-use, 3-in-1 solution for organic and conventional growers.
RevoCURB™ is a new OMRI-listed, 3-in-1 soil treatment designed to enhance crop health and yield by targeting plant parasitic nematodes, microbes, and pre-emergent weed seeds. Exempt under FIFRA 25(b), RevoCURB offers a 0-hour restricted entry interval (REI), no restrictions on maximum residue levels, minimal requirements for personal protective equipment, and no need for buffer zones. RevoCURB utilizes the power of Smart Blend Technology and four essential oils – thyme, clove, garlic, and cinnamon to provide control through multiple complementary modes of action. These oils disrupt cellular membranes on contact, inhibit nematode egg hatching, impact the nervous systems of juvenile nematodes present in the soil, causing paralysis and death, vaporize within the soil column, repelling pests and delaying repopulation and suppress weed seed germination.
“These contact and repellency modes of action work in tandem upon application of RevoCURB to disrupt pest lifecycles and prepare soils for planting.” – Emma Trainer, Scientist at Kemin Crop Technologies.
RevoCURB should be applied 14 days prior to planting or post-harvest and watered in per label directions to maximize efficacy and the zone of protection without harming crop seeds, seedlings, and plugs.
Field trial to assess the effectiveness of RevoCURB on root-knot and stunt nematode populations on cucumber. San Luis Obispo, California (Credit: Bradley Booker at Pacific Ag Research) (SD-25-28093)
RevoCURB protects young crops from multiple soil pest pressures, allowing for healthier plants and greater yields. Because it’s free from buffer zone requirements, REI, and residue restrictions, RevoCURB is ideal for transitional areas and organic acreages – bringing flexibility and safety where conventional fumigants fall short.
Vansickle, J.J.; Smith, S.; and R. Weldon (2009). Impacts of EPA proposed buffer-zone restrictions on profitability of Florida strawberry growers. University of Florida Institute of Food and Agricultural Sciences; FE795.
Bolda, M.P.; Dara, D.K.; Daugovish, O.; Koike, S.T.; Ploeg A.T.; Brown, G.T.; Fennimore, S.A.; Gordon, T.R.; Joseph, S.V.; Westerdahl, B.B.; and F.G. Zalom. Non-fumigant alternatives for soil disinfection. UC IPM Pest Management Guidelines: Strawberry. UC ANR Publication 3468. University of California Agriculture and Natural Resources, Davis, CA. https://ipm.ucanr.edu/agriculture/strawberry/non-fumigant-alternatives-for-soil-disinfestation/#gsc.tab=0
Lopes, E.A.; Canedo, E.J.; Gomes, V.A.; Vieira, B.S.; Parreira, D.F.; and W.S. Neves (2022). Anaerobic soil disinfection for the management of soil-borne pathogens: a review. Applied Soil Ecology, 174.
