Why neonicotinoids are bad for bees

Bee numbers are rapidly dropping and there is evidence that neonicotinoid pesticides are partly to blame. The evidence against these chemicals is strong enough that in April 2013 the EU suspended three types of neonicotinoid pesticides for two years - clothianidin, imidacloprid and thiametoxam. New evidence is revealing that other species are being impacted by neonicotinoids too, including other insects, birds, fish and small mammals. It is also being revealed that the chemicals are persisting in soils and leaching into waterways. As the evidence against the use of neonicotinoids continues to mount we are calling for a permanent ban on all nenonicotinoids now. You can help us to achieve this by becoming a member of the Soil Association, find out more here.

More information

  • 'Five neonicotinoid dressed maize seeds, or 32 dressed oilseed rape seeds, are enough to kill a partridge', revealed leading bee researcher Professor Dave Goulson in a session on how to save bees and other pollinators at the Soil Association Conference 2014, read more from the session in a blog coming soon.
  • 'Neonicotinoids impact all sepcies that chew a plant, sip its sap, drink its nectar, eat its pollen or fruit', this is just one of the findings of the Worldwide Integrated Assessment on Systemic Pesticides, read the full report here.
  • The Soil Association submitted evidence to the UK Environmental Audit Committee's inquiry into Insects and Insecticides in November 2012. The submission provides a useful summary of the evidence against neonicotinoids. View the paper submitted here.
  • Pesticide Action Network have produced a series of factsheets which can be viewed here.

How neonicotinoids work

Neonicotinoids work as an insecticide by blocking specific neural pathways in insects’ central nervous systems. The chemicals impair bees’ communication, homing and foraging ability, flight activity, ability to discriminate by smell, learning, and immune systems – all of which have an impact on bees' ability to survive. 

It seems bees genetic make up makes them particularly vulnerable to neonicotinoids. Recent mapping of the bee genome has revealed that bees’ capacity to detoxify chemicals is much lower than other insects. Instead bees have two strategies to protect themselves. On the first day of foraging in a new area, scout bees are sent out first to taste the nectar and pollens – if any are adversely affected they will be expelled from the hive immediately, and the colony will avoid the area.

In addition, once foraging begins, nurse bees in the hive clean foragers each time they return. These strategies protect the colony from mass exposure to lethal doses of chemicals, but they do leave honey bees particularly susceptible to sub-lethal exposures to any contaminants they encounter.

The other really important factor is the complex behaviour of honeybee colonies. For example, the 10,000 forager bees in a typical hive need to co-ordinate their quest for nectar – and they do this through the famed ‘waggle dance’, which communicates the flight direction and distance to sources of nectar. The complexity and precision of these dances is breathtaking, and success relies on the integrity of a nervous system where each synapse is crucial. It is no surprise then that honey bees have been shown to have a higher number of neurological receptors than other insects.

Honey bees live and work as a colony, not as individuals; what seems to be happening is that the cumulative impact of small doses of nenoicotinoids on thousands of bees over time is affecting individual bee's ability to work and communicate effectively as part of a colony. Because lots of bees in each colony are behaving sub-optimally this can lead to the sudden, and devastating, outcomes that we've been witnessing in recent years.

The Soil Association believes that there is already enough evidence to justify an immediate and permanent ban on neonicotinoids today.

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