Broad spectrum insecticides are toxic to nearly all insects

It’s that time of year again where signs start popping up on street corners and cards appear in mailboxes from businesses offering to eradicate mosquitoes and ticks from our backyards.

While some of these services offer a garlic spray alternative, most, if not all, primarily use pyrethroids – synthetic and longer lasting forms of the natural chemical pyrethrin – to spray the perimeter of residential properties and areas where mosquitoes and ticks primarily rest. These services often offer to spray for spiders, too, which is ironic because spiders are harmless and in fact provide a small element of natural pest control themselves, by eating the very insects people wish to be rid of.

Companies tout their sprays as being “safe” because they are non-toxic to mammals. What they don’t highlight is that these broad spectrum insecticides are toxic to nearly all insects who come in contact with them, including bees, butterflies, dragonflies, fireflies,ladybugs, etc. They are also highly toxic to many aquatic species should they end up in backyard ponds or other bodies of water.

Various studies determined that bees exposed to pyrethroids have been found to experience significant disorientation, decreased fecundity, reduced movement and travel, reduced social interaction, and death. These impacts were recorded as far out as 28 days after spraying. Studies also show that caterpillars and butterflies have a very high sensitivity to insecticide residue on leaves, and one study of commonly used pesticides showed that pyrethroids were the most lethal of the chemicals tested to butterflies at all life stages. One scientific study found that monarch caterpillars were harmed or killed by pyrethroids as much as three weeks after spraying, confirming a longer term residual impact from these chemicals in the environment.

Spraying our properties for mosquitoes can do great harm to pollinators, even when flowering plants are avoided. Sprays can drift up to 100 metres on application, depending on the wind, and can contaminate flowers and other vegetation for anywhere from days to months after spraying.

How can we justify this unnecessary use of pesticides?

We are in the middle of a biodiversity crisis, with insects on the frontline. Without insects, the world as we know it would cease to exist, yet due to human pressures we have lost 75 per cent of these tiny, critical lifeforms in the past 50 years. This year alone, beekeepers in the United States lost up to 70 per cent of their honeybee colonies in a catastrophic collapse, for reasons which are not yet clear.

These losses are already impacting agricultural productivity in a significant way. Across the globe, fruit and vegetable production is down as much as five per cent annually as a direct result of inadequate pollination, which experts estimate leads to approximately 500,000 premature deaths each year.