Neonicotinoids' Impact on Pollinators

Excerpted from: Dancing With Bees, a journey back to nature, by Brigit Strawbridge Howard

Rachel Carson and book cover of The Silent Spring

In 1962, Rachel Carson published The Silent Spring which was a warning of the dangers of a revolutionary new pesticide DDT. She had noticed that in the 1950s and 1960s it was responsible for, among other things, the crashing of bird populations. DDT was banned in the United States in 1972 but it appears that history is repeating itself and we are fast approaching a time when it might be said, "The summer afternoons are strangely silent when they were once filled with the gentle bussing of bees."

A film documentary called 'Rachel Carson' produced by American Experience may be seen on Amazon Prime.

The culprit this time is another revolutionary group of pesticides called Neonicotinoids ('neonics' for short). They were first introduced in the 1990s and are currently the world's most widely used insecticide. Over 140 different crops including soy, corn wheat, cotton, legumes, potatoes, sugar beets, sunflowers, rapeseed and flax are treated with neonics.

A Potent Neurotoxin

Neonics are neurotoxins designed to attack an insect's central nervous system causing paralysis and eventually death. There were designed specifically to target agricultural pests such as vine weevils, aphids, whiteflies, Colorado potato beetles and termites. The damage they have caused over the last two decades to other insects, including bees, has been devastating.

Neonics are neurotoxins designed to attack an insect's central nervous system causing paralysis and eventually death. The damage they have caused over the last two decades to insects, including bees, has been devastating.

Pesticide Use Then And Now

In the past, we were able to 'see' pesticides since they were sprayed onto crops and we could wash off many of the contact chemicals. With neonics, though some are sprayed onto foliage, the majority are invisible to since they are applied as seed and bulb dressings or as soild dressings. Neonics are systemic, which means the chemicals are taken up by the entire plant – roots, leaves, fruits, flowers, pollen and nectar.

Previous forms of pesticide tended to be applied reactively, that is, after a pest had been identified in an area. In contrast, neonics are used prophylactically, which means crops (e.g., between 80-100% of US corn) are now grown from treated seeds or treated soil. This is being done as a safeguard against the possibility of an attack by the pesticide's target insect. This is like taking antibiotics throughout the year in case you might catch a cold.

Dangers of Being Water Soluble

Neonics are water soluble which means they can remain in the soil for a number of years. Only 5% of what is applied to the seeds is actually taken up by the plants. The remaining 95% of the pesticides leach into the soil. and because they are water soluble, migrate via the ground water into nearby streams and waterways.

Neonics also get sucked up from contaminated soil – not only by subsequent years of crops grown in the treated field but also by the wild flower margins along the edges of the fields. Many of those wild flower margins were planted or allowed to grow specifically to support pollinators.

Margins and waterways weren't intended to be treated with neonics, but they have been which has resulted in sustained exposure to bees, moths, butterflies, hoverflies and aquatic invertebrates. Declines in the insects can cause shortages in the food chain for insect-eating bats, amphibians and birds.

Sublethal Effects

Early studies of the effects of neonics appeared to show that they were safe for bees. However, that was because only the immediate lethal effects of the pesticide were investigated. Unfortunately the sublethal effects were NOT tested before they were used in our fields.

When the effect of neonics first began to be notices, concerns were focused on honey bees. This was around the time of Colony Collapse Disorder (CCD) and neonics were suspected to be one of the root causes. But now it is clear that bumble bees and other invertebrates are also affected. This group of insecticides are NOT safe for bees despite reassurances. When bees collect pollen and nectar for their brood to feed on, neither they nor their larvae can escape the neurotoxin's effects.

Neonics are water soluble which means they can remain in the soil for a number of years. Only 5% of what is applied to the seeds is actually taken up by the plants. The remaining 95% of the pesticides leach into the soil.

In response to concerns about both the lethal and sub-lethal effects of neonics on wildlife, the EU banned three of the most widely used neonics in 2018.

Graphic showing impact of Neonicotinoids

Chronic Effects On Bees

Scientific evidence collected over the last decade or so proves that neonics produce numerous chronic symptoms in bees such as:

Interfering with their navigation systems
Disrupting their foraging behavior
Disrupting their ability to communicate
Impairing their immune systems
Reducing reproductive success
Residues in nests of solitary bees may be linked to fewer egg cells.

Farmers And Neonics

There are some who believe that key crops will fail if seeds, plants and soils are NOT treated with neonics. It is true that failing crops are a concern however, it is also a concern if there are no pollinators left to pollinate the crops

Closing Comments

Nearly 60 years ago we learned the painful consequences of using DDT from Rachel Carson and her world-changing book. It is important for us to listen – and really hear – whether the world's soundscapes are again growing silent.

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