Skip to main content

Neonicotinoids: Are they killing our bees?


In April, the EU banned the use of neonicotinoid pesticides for two years starting in December because of concerns over their effect on bees.  The use of these pesticides will not be allowed on flowering crops that attract bees or by the general public, however winter crops may still be treated. Fifteen countries voted for this ban, with eight voting against it (including the UK and Germany) and four countries abstaining.

Neonicotinoids were originally thought to have less of an impact on the environment and human health than other leading pesticides. They are systemic insecticides, which means they are transported throughout the plant in the vascular system making all tissues toxic to herbivorous insects looking for an easy meal. The most common application in the UK is to treat seeds before they are sown to ensure that even tiny seedlings are protected against pests.

Image by Kath Baldock
The major concern over neonicotinoids is whether nectar and pollen contains levels of pesticide is high enough to cause problems for bees. It has already been shown that they do not contain a lethal dose, however this is not the full story. Bees live in complex social colonies and work together to ensure that there is enough food for developing larvae and the queen. Since neonicotinoids were introduced in the early 1990s bee populations have been in decline and there is a growing feeling of unease that the two may be connected. Scientific research has provided evidence both for and against a possible link leaving governments, farmers, chemical companies environmentalists and beekeepers in an endless debate about whether or not a ban would save our bees.

Several studies on bees have shown that sublethal levels of neonicotinoids disrupt bee behaviour and memory. These chemicals target nicotinic acetylcholine receptors, one of the major ways that signals are sent through the insect central nervous system. Scientists at Newcastle University recently showed that bees exposed to neonicotinoids were less able to form long-term memories associating a smell with a reward, an important behaviour when foraging for pollen and nectar in the wild. 

Researchers at the University of Stirling fed bumble bee colonies on pollen and sugar water laced with neonicotinoids for two weeks to simulate field-like exposure to flowering oil seed rape. When the colonies were placed into the field, those that had been fed the pesticides grew more slowly and produced 85% less queens compared with those fed on untreated pollen and nectar. The production of new queens is vital for bee survival because they start new colonies the next year. Studies in other bee species have found that only the largest colonies produce queens, so if neonicotinoids have even a small effect on colony size it may have a devastating effect on queen production.

So why does the government argue that there is not enough scientific evidence to support a ban on neonicotinoids?

Image by Kath Baldock
In 2012, the Food and Environment Research Agency set up a field trial using bumble bee colonies placed on sites growing either neonicotinoid-treated oil seed rape or untreated seeds. They found no significant difference between the amount of queens produced on each site, although the colonies near neonicotinoid-treated crops grew more slowly. The study also found that the levels of pesticide present in the crops was much lower than previously reported.

I personally think that both laboratory and field studies bring important information to the debate, however neither has the full answer. Whilst more realistic, the government’s field trial suffered from a lack of replication, variation in flowering times and various alternative food sources available to bees. Only 35% of pollen collected by the bees was from the oil seed rape plants, so where oil seed rape comprises the majority of flowering plants available to bees the effect on neonicotinoids may be more pronounced. The laboratory research can control more variables to establish a more clear picture, however the bees in these studies were often given only neonicotinoid-treated pollen and nectar to eat, which clearly is not the case in a rural landscape. Flies and beetles have been shown to avoid neonicotinoids, which could mean that bees would find alternative food sources where possible. This would have a major impact on crop pollination.

We desperately need well-designed field studies looking at the effect of neonicotinoids on bees and the environment in general. Despite an EU moratorium on growing neonicotinoid treated crops, an allowance should be made for scientists to set up controlled field trials to study the effect of these pesticides on bees during the two year ban. It could be our only chance to determine the danger these chemicals pose to vital pollinators and the wider environment



This blog is written by 
Sarah Jose, Biological Sciences, University of Bristol

Sarah Jose

Popular posts from this blog

Powering the economy through the engine of Smart Local Energy Systems

How can the Government best retain key skills and re-skill and up-skill the UK workforce to support the recovery and sustainable growth? This summer the UK’s Department for Business, Energy and Industrial Strategy (BEIS) requested submission of inputs on Post-Pandemic Economic Growth. The below thoughts were submitted to the BEIS inquiry as part of input under the EnergyREV project . However, there are points raised here that, in the editing and summing up process of the submission, were cut out, hence, this blog on how the UK could power economic recovery through Smart Local Energy Systems (SLES). 1. Introduction: Factors, principles, and implications In order to transition to a sustainable and flourishing economy from our (post-)COVID reality, we must acknowledge and address the factors that shape the current economic conditions. I suggest to state the impact of such factors through a set of driving principles for the UK’s post-COVID strategy. These factors are briefly explained belo

Farming in the Páramos of Boyacá: industrialisation and delimitation in Aquitania

Labourers harvest ‘cebolla larga’ onion in Aquitania. Image credit: Lauren Blake. In October and November 2019 Caboteer  Dr Lauren Blake  spent time in Boyacá, Colombia, on a six-week fieldtrip to find out about key socio-environmental conflicts and the impacts on the inhabitants of the páramos, as part of the historical and cultural component of her research project, POR EL Páramo . Background information about the research can be found in the earlier blog on the project website . Descending down the hill in the bus from El Crucero, the pungent smell of cebolla larga onion begins to invade my nose. The surrounding land transforms into plots of uniform rows of onion tops at various stages of growth, some mostly brown soil with shoots poking out along the ridges, others long, bushy and green. Sandwiched between the cloud settled atop the mountainous páramos and the vast, dark blue-green Lake Tota, all I can see and all I can smell is onion production. Sprinklers are scattered around, dr

IncrEdible! How to save money and reduce waste

The new academic year is a chance to get to grips with managing your student loan and kitchen cupboards. Over lockdown the UK wasted a third less food than we usually would. This is brilliant, as normally over 4.5 million tonnes of edible food is wasted from UK homes every year. For students, it’s even higher. The average cost of food waste per student per week is approximately £5.25 - that's about £273 per year !  It’s not just our bank accounts that are affected by food waste – it’s our planet too. The process of growing, making, distributing, storing and cooking our food uses masses of energy, fuel and water. It generates 30% of the world’s CO₂ greenhouse gas emissions. The same amount of CO₂ as 4.6 million return flights from London to Perth, Australia! So it makes sense to keep as much food out of the bin as possible, start wasting less and saving more.  Start the new term with some food waste busting, budget cutting, environment loving habits! Here’s five easy ways to reduce