The Limitations of Fumigants in U.S. Agriculture: Buffer Zones and Organic Farming Challenges

Fumigants are a cornerstone of conventional agriculture in the United States, offering a powerful solution to combat soil-borne pests and diseases. However, the use of fumigants also has significant limitations, particularly in the context of 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 to soil to eliminate pests, pathogens, and weeds prior to planting to protect young crops and improve plant vigor and harvestable yields.

Despite their benefits, most fumigants pose risks to human health and the environment, leading to strict regulations on their use, application timing, permitting, and buffer zones^1,2. 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 Europe^2,3.

Buffer Zone Restrictions

To mitigate the risks associated with fumigants, the Environmental Protection Agency (EPA) has implemented stringent buffer zone requirements across the United States². These buffer zones are areas bordering fumigated fields where fumigant application is not allowed to prevent exposure of the general population to toxic gases. The size of these zones depends on factors such as the type of fumigant, application method, local environmental conditions, and distance to public spaces, including schools and hospitals.

While buffer zones are essential for public safety and conservation efforts, they significantly reduce the amount of usable farmland. Farmers often leave these transitional portions of their fields untreated, which can lead to uneven pest control and reduced crop yields⁴. Additionally, the administrative burden of complying with buffer zone regulations, such as posting warning signs and maintaining detailed fumigant management plans, adds to the complexity and cost of using these chemicals².

Additional Limitations of Fumigants

Beyond buffer zone requirements, fumigants come with other significant limitations:

• Cost: Fumigation is an expensive practice, requiring substantial investment in chemicals, labor, and compliance with regulatory requirements. The high costs can be prohibitive for small-scale farmers.
• Equipment: Specialized equipment is necessary for the safe and effective application of fumigants. This includes shanking application equipment, calibrated applicators, tarping systems, and enhanced personal protective gear, all of which add to the overall expense.
• Application Limitations: Fumigants must be applied under specific conditions to ensure efficacy. Factors such as soil temperature, moisture levels, weather conditions, and proper calibration of equipment are critical. Failure to meet these conditions can result in reduced efficacy or unintended environmental impacts.
• Environmental Risks: Fumigants are highly volatile and can drift off-site, posing risks to nearby communities and ecosystems. Misapplication or accidents can lead to contamination of water sources and 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:

1. Soil Solarization

This method involves covering fallow fields with plastic during the hottest months to create a greenhouse effect, trapping solar energy as heat. The heat generated can kill pathogens, pests, and weed seeds. Solarization is particularly effective in regions with consistently high summer temperatures, but this process requires leaving fields covered for extended periods as long as 4-8 weeks. For many growers, this timeline may be prohibitive as the temperatures required for effective treatment occur during peak growing seasons.

2. Anaerobic Soil Disinfestation (ASD)⁶

This technique involves incorporating organic materials like rice bran or mustard seed meal into the soil, saturating it with water, and covering it with plastic to create anaerobic conditions. As oxygen is depleted, aerobic soil-borne pathogens and pests that rely on oxygen cannot survive. Additional anaerobic microbial species that rely on carbon or sulfur instead of oxygen may flourish and produce byproducts that make it even harder for aerobic soil-borne pathogens to survive. 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 requires organic carbon inputs and high volumes of water. Furthermore, if fields are drained before anaerobic conditions are reached in the soil, the resulting efficacy is greatly reduced.

3. Crop Rotation and Cover Cropping

Both crop rotations and cover cropping can disrupt pest life cycles and improve soil health, reducing the need for chemical interventions in an area. However, these practices are not always sufficient to knock down heavy infestations without additional input.

4. Biological Controls

The use of beneficial microorganisms or natural predators can help manage pest populations effectively by preying on or competing against pest populations. While beneficial populations can help ensure healthy fields, it is most effective when paired with other control method. Furthermore, using beneficial species properly requires special attention to the choice of species, application timing, and other environmental factors which may influence the success of the beneficial population.

While methods like solarization and ASD are effective, they often require more time, labor, and expertise compared to conventional fumigation and may have lower efficacy against heavy pest infestations. Softer interventions such as cover cropping and the use of beneficial populations can help keep a field clear of invasive pests, but these practices may not control heavy infestations and are best when paired with a comprehensive pest management system.

Introducing RevoCURB™, a safe-to-use, 3-in-1 solution for both conventional and organic growers

How RevoCURB Works

Powered by Kemin’s proprietary formulation, RevoCURB combines four essential oils—thyme, clove, garlic, and cinnamon—to deliver broad-spectrum control of soilborne pests through multiple modes of action:

• Contact Action: Disrupts cellular membranes of soil pests and weed seeds on contact.
• Nematicidal Effect: Garlic and cinnamon oils inhibit nematode egg hatching and paralyze juvenile nematodes.
• Vapor Phase Repellency: Volatile compounds like diallyl sulfides and eugenol vaporize within the soil column, repelling pests and delaying repopulation into the treated area. 

This dual-action approach—contact kill and repellency—disrupts pest lifecycles and prepares the soil for healthy planting.

RevoCURB should be applied 14 days prior to planting and watered into soils according to label directions to maximize the product efficacy and the zone of protection without harming crop seeds, seedlings, and plugs. When used as directed, RevoCURB protects young crops from multiple soil pest pressures, allowing for healthier established plants and greater yields at harvest.

RevoCURB is an ideal solution for all growers and can be used with no restrictions in otherwise difficult-to-control buffer zones and transitional fields, as well as all conventional and organic acreages.

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References:

1. Panth, M. & Hassler, S. and F. Baysal Gurel (2020). Methods for Management of Soilborne Diseases in Crop Production. Agriculture, 10.
2. United States Environmental Protection Agency. Soil Fumigant Toolbox. https://www.epa.gov/soil-fumigants
3. European Commission. European Community Management Strategy for the phase-our of the critical uses of methyl bromide. April 2009. https://ozone.unep.org/sites/default/files/additional-reported-information/MeBr_Submissions/EC%20Management%20Strategy%20for%20Methyl%20Bromide.pdf
4. 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.
5. 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
6. 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 soilborne pathogens: a review. Applied Soil Ecology, 174.