Rodent control in agriculture is hugely important. Rats have been declared to be pests by most provincial governments, making it possible for farmers to eradicate colonies when detected. In California, rodents destroy an estimated US$500 million worth of crop production, or about 7% of total production value. Crop losses in Canada are estimated to range from $15-30 million annually, with livestock forage production capability being reduced by up to 49%.
In the Canadian Prairies, gopher control has long been an important issue, with gophers being one of the worst pests in the Canadian prairies. With their diets consisting of wild plants and domesticated crops, left uncontrolled, gophers can rapidly multiply, causing significant damage to agricultural crops. 100 years ago, school children were given the day off from school to kill gophers, which were estimated to destroy 250,000 acres of crop production. At this time and into the 1930s, provincial governments would pay 1¢ per gopher tail as part of an incentive to help control gopher populations.
Many chemicals have been used as part of the efforts to control rodent populations. Arsenic has a long history of being used to control various rodent populations. Chemical powders such as zinc phosphide, thallium sulfate and calcium cyanide have all been used for rodent control. Fumigants such as sulfur dioxide, carbon monoxide, hydrogen cyanide and methyl bromide are also effective rodenticides.
Following WWII, the chemical structure of strychnine was first determined by Sir Robert Robinson, which was first synthesized in a lab in 1954 by Robert Woodward. Both men would receive Nobel Prizes for their work. It rapidly gained popularity as an efficient means of controlling gopher populations.
Strychnine would be mixed with grain at a low rate of concentration and placed inside of gopher burrows where the gophers would eat the grain and die in their holes. The use of liquid strychnine ended in 1992, but Health Canada has provided emergency exemptions in instance of several gopher infestations, such as in Saskatchewan in 2008.
In 2020, the Pest Management Review Agency (PMRA) reviewed the use of strychnine and concluded that there were risks to non-target organisms, including species at risk and cancelled the registration of strychnine for use in Canada. Sales of strychnine ended in 2023, creating a significant challenge for farmers to control gophers as there were very few effective control mechanisms remaining outside of shooting gophers.
Farmers in southern Saskatchewan were particularly hard hit in the spring of 2024, with some farmers losing hundreds of acres of crop and being forced to reseed fields due to crop damage from gophers. This reseeding cost farmers thousands of dollars in the cost of new seed and fuel.
The problem that was instantly created by banning strychnine is that there is no efficient alternative. Europe’s politicization of its risk assessment system has witnessed this as well. In 2013, the European Union banned the use of noenicitinoids for the production of crops. This ban was to be phased in over a three-year period. Two years after the ban was fully implemented, sugar beet yields in France plummeted by up to 80% due to the lack of viable alternatives. In 2021 neonics were allowed to be used again for a period of three years. This exemption was renewed in 2025 for a further three years. Rapeseed production in the UK dropped by nearly 50% due to the ban on neonics.
Canada’s PMRA has fallen victim to the politicization of risk assessment due to pressure from activists, both academics and organizations. The risk of using strychnine had not changed in the preceding 50 years, as its use was entirely dependent on gopher populations. There was always a risk to non-target organisms, which is wildlife that might eat poisoned gophers. The risk of this was unchanged, yet due to pressure from academic and environmental activists, the renewal of strychnine was refused, which resulted in the announced phase out in 2020, with use phased out by 2023.
Farmers have always been efficient in their use of all farm pesticides and the use of strychnine is no different than any of the others used. The February 2026 announcement by Health Canada granting an exemption for the use of strychnine confirms just how erroneous the initial decision was. The attempt to politicize Canada’s risk assessment system by activists has had exactly the same disastrous outcome as it did in Europe. This reversal by the PMRA confirms the importance of relying on evidence for policy decisions.
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