Pesticides of most concern

Tractor spraying pesticides at corn fields © fotokostic


Neonicotinoids are widely used insecticides with three main applications, as a seed coating for crops, as sprays for crops and domestic gardens, and as an externally applied flea treatment for pets. It has been estimated that crop plants absorb about 5% of the neonicotinoid active ingredient, with the majority dispersing into the surrounding environment. Neonicotinoids appear to concentrate in the soil surface, can leach through the soil and contaminate groundwater and are highly toxic to aquatic insects at miniscule concentrations. In addition to the negative impacts of neonicotinoids on bees, evidence indicates that persistent, low levels of neonicotinoids can have detrimental impacts on a wide range of free-living organisms. Mayflies, caddisflies, dragonflies, flies and beetles tend to be most sensitive to neonicotinoid pollution.

Hairy Dragonfly (Brachytron pratense) © Charlie Jackson (Flickr, CC) Hairy Dragonfly (Brachytron pratense) © Charlie Jackson (Flickr, CC)


Glyphosate (GLY) herbicide use is increasing, and GLY is currently the most used herbicide in the world. As a consequence of its widespread application in the agriculture and aquaculture sectors, high concentrations of GLY have been detected in soil and aquatic environments. Studies have shown that constant long-term exposure of GLY and Glyphosate-based herbicides (GBHs) are most toxic to earthworms, and can affect biological responses of marine invertebrates. Glyphosate has however become the most high-profile example of the issue of co-formulant toxicity. On its own Glyphosate is not very toxic to plants, so it needs another chemical to be mixed with it that damages cells and enables glyphosate to enter the cells. The co-formulants are secret ingredients, although it has subsequently become apparent that one of the commonly used Glyphosate co-formulants, tallow amine, was banned in the EU due to health concerns. It is not known what chemical has replaced the tallow amine. Of course, Glyphosate and other herbicides also have the effect of reducing the abundance of flowering plants in the countryside, reducing forage for wild pollinators.

Lob Worm (Lumbricus terrestris) © Keiron Derek Brown Lob Worm (Lumbricus terrestris) © Keiron Derek Brown


Despite their long history of use in agriculture, the study of the environmental impacts of pyrethroids on wildlife has been late arriving. The historical paucity of evidence relating to insecticide sprays and pollinators in field margins is unfortunate considering that pyrethroids are known to impact on beneficial invertebrates. They significantly reduce the abundance of caterpillars, sawfly larvae and moths. Pyrethroids are widely detected in pollen and impact bees – recent science showing that pyrethroids negatively affect the foraging and pollination success of bumblebees and solitary bees.

Flupyradifurone (FPF)

FPF is a newly developed neonicotinoid [1] It was claimed to be safe for bees, however, studies indicate they are highly toxic to honeybees. Just like the banned neonicotinoids, FPF targets insect nicotinic acetylcholine receptors and have similar effects on bee health.FPF’s survival toxicity is more than five times higher than the N-cyanoamidine neonicotinoids (acetamiprid, thiacloprid). FPF was the only pesticide with an environmental hazard associated with it, added to the 2019 PAN International List of Highly Hazardous Pesticides (HHPs).

Bumblebees on globe thistle © Dan TP Bumblebees on globe thistle © Dan TP


Sulfoxaflor is another neonicotinoid insecticide that targets the nicotinic acetylcholine receptors. Sulfoxaflor lasts for a significantly shorter time in the soil and is less toxic to aquatic invertebrates than the other neonicotinoids. However, it is 97-115 times more toxic than thiacloprid and acetamiprid to honeybees and more toxic to earthworms than all the other neonicotinoids. In water, sulfoxaflor is less likely to leach than the main three neonicotinoids but has high solubility in water.

Alcohol ethoxylates

Alcohol ethoxylates are not an active ingredient, but a secret pesticide co-formulant that can cause 30% mortality and a range of sublethal effects in bumblebees. While we know these chemicals are often used in one of the commonest fungicide products, it is not possible to know what pesticide products contain them. Obviously as this co-formulant is toxic to bees, in combination with some active ingredients it could be causing even greater harm.

Peacock Butterfly © Amy Lewis Peacock Butterfly © Amy Lewis

[1] After evidence of the environmental damage caused by neonicotinoids started to emerge the pesticide industry has tried to rebrand this chemical as not being a neonicotinoid, but here we use the original (and honest) chemical classification.