Background and scientific challenge
Neonicotinoids are a type of pesticide which have played a key role in protecting a wide variety of crops. They have been used extensively both in Europe and the rest of the world and have proven to be particularly important as a crop seed treatment where they are used to coat the seed before it is sown. As the crop grows the neonicotinoids are transferred to parts of the growing plant. When insect pests feed on the plants they feed at the same time on the neonicotinoids present in the plant’s tissues and so are killed.
This type of pesticide (called systemic) reduces the need to spray the crop with other types of pesticides (like pyrethroids) which may drift to contaminate waterways or kill other insects found on farmland that are not pests.
Unfortunately, pests are not the only animals to feed on crops. Bees, including honeybees, bumblebees and solitary bees, also feed on some crops. In Europe this is a particular problem with the pollen and nectar of flowering crops like oilseed rape and sunflower. Although bees play a vital role in pollinating such crops, the use of neonicotinoid pesticides may be accidentally poisoning them.
Potential effects on pollinators
The effect on the bees of feeding on pollen and nectar containing neonicotinoids may be very hard to detect. Bees are not likely to die instantly, something that would have been identified before the pesticide was licenced for use. Rather the effects are subtle, for example honeybees may become disorientated when feeding and so fail to return to their hives, or bumblebees may produce fewer queens than would normally be expected. These effects are often referred to as "sub-lethal" and may affect the bee populations over a long period of time. If this is the case it may affect the survival of honeybees and wild bees in European farmland.
This evidence for the effect of neonicotinoids on bees has highlighted a potentially huge problem with the pesticide. It led the European Union to provisionally ban neonicotinoid seed treatments when applied to mass flowering crops like oilseed rape. This ban came into effect from 2014, but will be reviewed in 2015. As concern over the effects of neonicotinoids on bees is relatively recent, much of the research used to support the ban was, by necessity, undertaken under laboratory conditions or at a small scale within a limited number of fields. These studies have been crucial in identifying a problem with neonicotinoids but there is now a need to support this research with large-scale studies.
This is particularly important as bees often forage over very large distances (eg 2-4 km for some bumblebees). By foraging over large distances bees may interact with the landscape in unexpected ways, for example, by feeding on other flowering plants not exposed to neonicotinoids in hedgerows and field margins.
We need to understand whether neonicotinoids used on crops like oilseed rape will affect how honeybees and wild bees survive under real world conditions found on working farms across Europe. Our research aims to address this issue for wild bees (bumblebees and solitary bees) by looking at the impacts of neonicotinoid seed treatments on oilseed rape in 33 farms across the UK, Germany and Hungary. On each farm we will sow large areas of oilseed rape (around 40 hectares) to replicate how this crop is grown under normal conditions in many parts of Europe. The research is part of a sister project looking at the same effects on honeybees.
The project (2015-16) aims to understand if there is an impact from exposing wild bees to oilseed rape treated with neonicotinoid seed treatments. We will look to see if this exposure affects not only the number of bees of different species that are found on farms, but also how successful they are in breeding and whether the pesticide has affected how likely they are to get different diseases. By undertaking this study across a large number of real farms we will also be able to see if the surrounding landscape, and with it the availability of other types of flower-rich habitats in which they can feed, may act to alter how neonicotinoids affect bees.
To do this we will use a variety of methods. The most important of these will involve putting out artificial colonies of the Buff-tailed bumblebee and releasing individuals of the Red Mason bee to see how successfully they breed. We will also see how successful other species of wild bee are at breeding on these farms by encouraging them to nest in specially designed ‘trap nests’. These are blocks of wood drilled with holes in which wild solitary bees like to make their nests.
By comparing how well the different types of bee do on farms where the oilseed rape has (the ‘treated’ sites) or has not (the ‘control’ sites) been treated with neonicotinoids we will be able to ask the following questions:
- Do neonicotinoid seed treatments applied to oilseed rape have measurable harmful effects on wild pollinator populations (bumblebees and solitary bees), which are both important for crop pollination?
- Does the smaller size and shorter longevity of these wild pollinator populations make them less resilient to sub-lethal doses of neonicotinoids than domesticated honeybees?
- Does neonicotinoid exposure reduces the complexity and stability of wild pollinator-parasitoid food webs?
- Are parasites and pathogens prevalent in wild pollinator populations and do they have negative impacts on populations?
- Do neonicotinoids also interact with the incidence of pathogens to have a synergistic negative impact on wild pollinator populations?
- Is there transmission of pathogens and parasites between domesticated honeybees and wild bees, and is this exacerbated by exposure to neonicotinoids?
- Can landscape structure and the quality of surrounding non-crop foraging resources mitigate the effects of pesticides and pathogens on wild pollinator populations, and the resilience of their trophic interactions?
We will use a powerful experimental infrastructure in Germany, Hungary and the UK to ask these questions.
The study will last one year and will involve close collaboration between pollinator ecologists and toxicologists at CEH, along with our collaborators at Eurofins (experimental implementation), Länderinstitut für Bienenkunde (disease analysis), Mike Edwards (Bee expert), Judy Webb (pollen grain analysis) and the Wildlife Farming Company (Agronomy). This project uses the large-scale experimental framework funded by Syngenta and Bayer CropSciences.