Agriculture is an insect-filled industry that has to do work to stay clean. Soil fumigants are a major controversy in this regard. With permits for outdoor cannabis growing on the rise, Health Canada's Pesticide Management Regulatory Authority (PMRA) approved a fumigant for cannabis farms – chloropicrine (trichloronitromethane).
Two fumigants are approved for Canada's outdoor cannabis cultures and are manufactured by Triest Ag Group Inc.
- Chloropicrin 100 liquid soil fumigant – 99% chloropicrin
- Pic Plus fumigant – 85.1% chloropicrin
Despite the recent PMRA approval of chloropicrin for cannabis farms, the fumigant is banned in other countries. The reason for its banned status in the EU is, for example, its risk of lung injury and its environmental toxicity. (1) So North America still seems to stand up against other countries that have banned chloropicrin, which is being done in parallel with a study published in Biomed Central. (2) As a result, certain American farmers avoid chloropicrin and sometimes prefer methyl bromide, which the EPA has phased out. (3.)
Thankfully, the two Canadian PMRA approved fumigants are strictly injected into the soil before cannabis is planted on the farm. However, chloropicrin can still be trapped in the soil and cause respiratory damage. (4) This fumigant caused over 1000 pesticidal diseases in California alone from 2000 to 2015. (2)
Photo courtesy UC Davis.
Is the soil better dead or alive for plants?
Chloropicrin can be used as a fumigant on cannabis farms to kill soil pathogens. Gassing the soil is simple and inexpensive. In addition, avoiding the dangers of chloropicrin is far less of a hassle than using healthy soil microbes to benefit the farm. And this particular fumigant can help promote a healthy soil microbe known as Trichoderma spp. Is known. (5) Chloropicrin therefore offers a great cost advantage.
This fumigant is most effective on soil diseases, but not on nematodes or invasive plants. (6)
In contrast, cannabis connoisseurs and some of the more experienced cultivators prefer a floor bed that is very much alive and full of life. Living soil produces far better crops than dead dirt, but the cost is far higher. On the other hand, it's also the reward. That is why good breeders know how to tame the beetles in their plants, and the first lesson takes place in the soil. Compost teas keep a soil bed active and healthy, which, however, completely contradicts the practice of soil fumigation.
Life versus Sterilized Growth Media
Not all growers are bold enough to get live soil beds because fumigants can provide crop protection at a much lower cost. The question is whether cheaper legal flowers will compete with high quality black market cannabis when the former are fumigated. Perhaps some will succeed with chloropicrine. Admittedly, the cannabis industry is familiar with sterilized soil and hydroponic media, just not large open-air farms that use an approved fumigant.
It is therefore difficult to say whether this practice will be included in a company's Integrated Pest Management (IPM) plans. Cheap weeds are rather tempting, however. Convenience, but also viability, is a good reason for farmers to ignore expressed concerns from consumers, artisan farmers, and the planet. But, given financial viability, can chloropicrin be considered the lesser of two evils in the face of harmful bacteria and other pests?
Shaft injection of a soil fumigant. Photo courtesy UC Davis.
Does Chloropicrin Affect Your Lungs?
For safety reasons, only approved fumigation specialists are allowed to use chloropicrin. However, exposure to four ppm chloropicrin for a few brief seconds may result in some incapacity for work. In addition, very transient exposure to fifteen ppm can cause respiratory tract injury. Undoubtedly, disease events due to the use of chloropicrin have occurred despite safety parameters. (7)
Unfortunately, it is not known whether chronic exposure to chloropicrin can cause developmental or reproductive harm, according to the CDC. However, the fumigant is highly toxic to fish and birds and harmful to bees. For this reason, the ground must be covered with special plastic for at least ten days after a farm has used this fumigant before cannabis is planted. (8th)
Is chloropicrine sustainable compared to living soil?
In general, according to publications in MDPI and Hindawi, there is great interest in moving away from soil fumigation and more into sustainable practices. (9, 10) In addition, a study by the Institute of Plant Protection and the Chinese Academy of Agricultural Sciences in Beijing, China used PCR sequencing to demonstrate the effects of chloropicrin on soil. (11)
This test can measure life forms in any medium by detecting pieces of DNA or RNA. Based on this study, chloropicrin has a significant negative impact on soil health around the fumigation point. (12) It also exacerbates the negative effects of fumigants on cannabis sales.
An alternative beyond living soil is to cover the soil with plastic and let the sun effectively cook the nasty insects in the dirt. This method is known as solarization and a similar technique is used to remediate cadmium contaminated soil.
Let us know your thoughts Now that a cannabis farm fumigant has been approved in the comments. Do you prefer cannabis from dead or living soils? For more information on pesticides approved for growing cannabis, please visit here next week.
Cover photo courtesy of the Government of Western Australia.
- European Food Safety Authority (EFSA), Anastassiadou, M., Arena, M., Auteri, D., Brancato, A., Bura, L., Carrasco Cabrera, L., Chaideftou, E., Chiusolo, A., Court Marques, D., Crivellente, F., De Lentdecker, C., Egsmose, M., Fait, G., Greco, L., Ippolito, A., Istace, F., Jarrah, S., Kardassi, D. Leuschner, R., Villamar-Bouza, L. (2020). Peer review of the pesticide risk assessment of the active substance chloropicrin. EFSA Journal. European Food Safety Authority, 18 (3), e06028. doi / 10.2903 / j.efsa.2020.6028
- Donley, N. The US lags behind other agricultural nations when it comes to banning harmful pesticides. Environmental health 18 44 (2019). doi / 10.1186 / s12940-019-0488-0
- Norman C. S. (2005). Potential Impact of Introducing a Methyl Bromide Phase-Out on US Strawberry Growers: A Case Study of a Nomination for a Critical Use Exemption Under the Montreal Protocol. Journal of Environmental Management, 75 (2), 167176. https://doi.org/10.1016/j.jenvman.2004.12.002
- M. Pesonen, M. Hkkinen, K. Rilla, R. Juvonen, T. Kuitunen, M. Pasanen & K. Vhkangas (2014). Chloropicrin-induced toxic reactions in human lung epithelial cells. Toxicology Letters, 226 (2), 236244. doi / 10.1016 / j.toxlet.2014.02.006
- De los Santos, Berta and Barrau, Carmen and Arroyo, Francisco and Porras, Marcelo and Medina-Minguez, Juan. (2003). Relationship between Trichoderma soil populations and strawberry fruit production in previously fumigated soils. HortScience: a publication from the American Society for Horticultural Science. 38.10.21273 / HORTSCI.38.7.1400.
- Sande, D., Mullen, J., Wetzstein, M. & Houston, J. (2011). Environmental Impact of Pesticide Use: A Case Study of Soil Fumigation in Florida Tomato Production. International Journal of Environmental Research and Public Health, 8 (12), 46494661. doi / 10.3390 / ijerph8124649
- Oriel, M., Edmiston, S., Beauvais, S., Barry, T., & O'Malley, M. (2009). Diseases Associated with Chloropicrine Use in California Agriculture, 1992-2003. Overviews of pollution and toxicology, 200, 131. doi / 10.1007 / 978-1-4419-0028-9_1
- Ajwa H., Stanghellini M., Gao S., Sullivan D., Khan A., Ntow W., Qin R. 2013. Emission reductions through fumigation with TIF justify regulatory changes. Calif Agr 67 (3): 147-137; 152. doi / 10.3733 / ca.v067n03p147.
- Hanschen, F. S .; Winkelmann, T. Biofumigation to Combat Replantation Disease – A Review. agronomy 202010, 425. doi / 10.3390 / agronomy10030425
- Laura Ney, Dorcas Franklin, Kishan Mahmud, Miguel Cabrera, Dennis Hancock, Mussie Habteselassie, Quint Newcomer and Brendan Fatzinger 2019, Article ID 5827585, 10 pages, 2019. doi / 10.1155 / 2019/5827585
- Li, J., Huang, B., Wang, Q., Li, Y., Fang, W., Yan, D., Guo, M. & Cao, A. (2017). Effect of chloropicrin fumigation on soil bacterial communities and genes encoding key enzymes involved in the nitrogen cycle. Pollution (Barking, Essex: 1987), 227, 534542. doi / 10.1016 / j.envpol.2017.03.076
- Zhang, S., Liu, X., Jiang, Q., Shen, G. & Ding, W. (2017). Legacy effects of continuous chloropicrin fumigation over 3 years on the composition of the soil microbe community and metabolic activity. AMB Express, 7 (1), 178. doi / 10.1186 / s13568-017-0475-1