Large Scale Field Trial:  Effects Of Neonic-Treated Crops On Bees

One of the major arguments used by the agrochemicals industry against the independent scientific evidence highlighting the danger of neonicotinoids to bees, is their claim that independent studies are laboratory studies, and that such studies represent unrealistic exposure scenarios in comparison with regulatory field studies.

Elsewhere on this website, I refute the arguments that the agrochemical regulatory field tests are more realistic and reliable (they are not), that independent lab tests lack value (they absolutely do have value), and in fact, there are many independent field trials highlighting the danger of neonicotinoids to bees.

On 30th June 2017, a large field experiment was published in Science.

A summary of some of the findings

Study title:  Country-specific effects of neonicotinoid pesticides on honey bees and wild bees
Authors: Woodcock et al., Science 356, 1393–1395 (2017) 30 June 2017

Study design:

  • Large field experiments to assess the effects of neonicotinoid-treated crops on three bee species
  • Study conducted across three countries (Hungary, Germany, and the United Kingdom).
  • Winter-sown oilseed rape was grown commercially with either seed coatings containing neonicotinoids (clothianidin or thiamethoxam) or no seed treatment (control).


Overall, ability to reproduce was negatively affected, for both wild bees and managed bees.  For example, in Hungary, negative effects on honey bees (associated with clothianidin) persisted over winter and resulted in smaller colonies in the following spring (24% declines).

However, the authors note that results were inconsistent across countries.  This is of no surprise to me.  Growing conditions will vary across countries, along with general species abundance, availability with local forage, and past profile of chemical usage.  In one sense, this illustrates the value of laboratory testing as forming part of the overall picture, since they allow conditions of research to be controlled.

“Taken together, our results suggest that exposure to neonicotinoid seed treatments can have negative effects on the inter-annual reproductive potential of both wild and managed bees, but that these effects are not consistent across countries.”

Interesting, although not surprising that when oil seed rape is considered a forage crop for managed honey bees, disease in hives is higher.  Multiple studies have indicated that neonicotinoids increase vulnerability to disease, through various means. 

Indeed, increased susceptibility to disease following exposure to the toxin is a sub-lethal effect Bayer CropScience have openly referred to as the key factor in their (neonic) Premise 200SC product’s efficacy against termites.

“The country-specific responses of honey bees and bumble bees strongly suggest that the effects of neonicotinoids are a product of interacting factors. This study has identified between-country differences in the use of oilseed rape crop as a forage resource for bees (affecting exposure to crop residues) and incidence of disease within hives. Both factors were higher for Hungarian and U.K. honey bees.”

One of the biggest criticisms of regulatory testing for agrochemicals is their failure to take account of sub lethal effects on bees.  For example, a toxin may not have immediate or rapid (acute) effects (e.g. mortality - death) through exposure to a large dose, but instead, teeny tiny amounts of the chemical (quite within the regulatory limits) can inflict harm on a bee colony or on individual bees, which may not be immediately visible, but slowly ensure the ultimate demise of the colony. 

In other words, if parts of a honey bee colony are affected, this will impair the whole colony in its entirety, since the bees behave collectively as a ‘Super-organism’, wherein all individuals play a crucial role to ensure the survival of the whole.  A small number of losses are to be expected and natural, but larger, sustained losses or impairment will ultimately harm the colony. 

Due to the long life cycle of honey bee colonies, these effects may take months to manifest (note that even Bayer CropScience admit their neonic product Premise 200SC takes about 3 months to kill a termite colony – termites being another Super-organism, so effects are not always immediately visible). 

It’s no surprise then, that some months after exposure to the poisons, a beekeeper is baffled by the demise of the honey bee colony, when the bees seemed to forage happily on neonic treated fields months before, and with apparently no immediate ill-effects.

With wild bees, we certainly have tremendous cause for concern.  No-one is managing them, they have shorter life cycles and smaller or no colonies, and the effects pass largely unscrutinized and below the radar of general awareness among the public.

The authors of the study state:

“Overall neonicotinoid residues were detected infrequently and rarely exceeded 1.5 ng g−1 (w/w). As such, direct mortality effects caused by exposure to high concentrations of neonicotinoids are likely to be rare. However, our results suggest that exposure to low levels of neonicotinoids may cause reductions in hive fitness that are influenced by a number of interacting environmental factors. Such interacting environmental factors can amplify the impact of honey bee worker losses (e.g., through sub lethal toxicity effects) and reduce longer-term colony viability.”

You can read the  study on this link (opens a new window).

It really is high time we moved away from using damaging poisons which harm bees, other pollinators and the environment, and instead worked with nature to produce food. 

Because at the end of the day, we never produced food without bees and other pollinators, but we did produce food without neonicotinoids.