I am a current York University (Toronto, Ontario) undergraduate student studying biology. I write to you because neonicotinoid pesticides are harming our biodiversity, agriculture, and economy, and their applications should be restricted. How do neonicotinoids work? Neonicotinoids, like nicotine, bind irreversibly to nicotinic acetylcholine receptors of a cell and stimulate a response. Whereas low to moderate activation of these cells (by acetylcholine) causes nervous stimulation, high levels overstimulate and block the receptors, causing paralysis and death in an organism. Since neonicotinoids are highly soluble, they are absorbed by the plant and distributed systemically, such as to flowers, pollen, and nectar. While neonicotinoids prevalent in the sap are efficient in controlling sucking and chewing insect pests, they negatively affect pollinators such as bees, butterflies, moths, and hoverflies.
Bees are exposed to neonicotinoids in the following ways: contaminated pollen and nectar, direct spray, residue contact, particles released during the planting of treated seeds, contaminated nesting areas, contaminated nesting materials, contaminated water, guttation fluid, extrafloral nectaries. The literature review by The Xerces Society for Invertebrate Conservation states that studies show daily sublethal doses of neonicotinoids impair learning, motor activity, memory, navigation, and foraging behaviour, and reduce brood production and food stores in honey bees. C. Sandrack et al.’s research shows that bumblebees produce 85% fewer queens per colony when exposed to field-realistic concentrations of imidacloprid, hampering colony growth. Neonicotinoid exposure can also cause bee immune deficiency and interact with other factors such as viruses or parasites to weaken colony health and increase susceptibility to Colony Collapse Disorder.
Why are bees so important? Pollinators, such as bees, support the reproduction of nearly 85% of the world’s flowering plants and 35% of global crop production. They are also a keystone species in most terrestrial environments: they pollinate seeds and fruits and feed various species from songbirds to grizzly bears. Pollinators support biodiversity, agriculture, and the economy.
Along with a risk to pollinators, the use of systemic insecticides poses a risk to other beneficial flower visitors that prey upon crop pests, recycle organic matter, feed other wildlife such as songbirds, or simply contribute to biodiversity. Neonicotinoid residues eventually seep into surface waters or leach into groundwater, contaminating aquatic invertebrates and thereby indirectly reducing populations of fish, birds, bats, frogs, and other animals that consume them. Neonicotinoids are also toxic to ants, termites, parasitoids, aquatic insect larvae, decomposer amphipods, woodlice, and most crustaceans.
Have other countries executed any precautionary measures? The European Union has banned three neonicotinoids – clothianidin, imidacloprid and thiametoxam. The European Food Safety Agency (EFSA) found that there were “high acute risks” to a wide range of organisms both on land and water, from use of these three insecticides. EFSA also stated that recent research suggests that acetamiprid and imidacloprid “may affect the developing human nervous system”.
Ontario has restricted the use of neonicotinoids requiring farmers and other commercial growers to apply for permits to plant seeds treated with neonicotinoid insecticides. I believe that Health Canada (Pest Management Regulatory Agency) should restrict neonicotinoids to applications that will not affect non-target species such as pollinators, until we have data on how neonicotinoid use on a specific plant may be managed to provide pest protection without exposing beneficial insects to sublethal or lethal levels in nectar and pollen.
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