Insects and Insecticides

Written evidence submitted by Dr Lynn Dicks, University of Cambridge


1. Wild bees and other pollinating insects are known to be declining in the UK and elsewhere in response to multiple interacting pressures, including the use of pesticides.

2. There is an urgent need for data on the actual exposure of wild pollinators to neonicotinoids or combinations of pesticides in their natural environment.

3. The Defra project (PS2371) that is supposed to fill this knowledge gap seems unlikely to. I cannot scrutinise the methods, but as described it is a small case study with a potential methodological flaw.

4. Recent evidence on the sub-lethal effects of field-realistic levels of neonicotinoids on bumblebees shows that serious implications for bumblebee colonies are possible.

5. No similar evidence has been published for solitary bees or other flower-feeding insects.

6. There is a lack of transparency in the pesticide regulatory system. The details of studies supporting the regulatory assessment are inaccessible.

7. There are many alternative farm management measures to enhance the natural pest control service provided in farmed ecosystems. My team at Cambridge are compiling a synopsis of scientific evidence on the effectiveness of these.


1. Wild pollinators are declining


1.1 This document considers wild pollinators native to the UK . Following the UK National Ecosystem Assessment (Smith et al. , 2011) this includes all flower-visiting insect groups that have the potential to pollinate crops or wild flowers, including bees, flies, wasps, beetles, butterflies and moths. It does not consider the managed honey bee Apis mellifera .

1.2 Wild insect pollinators pollinate many crops and wild plants at no direct cost to farmers or land managers. For crops, the pollination service is currently valued at £510.2 million (Breeze et al. , 2012) . Under favourable assumptions for honey bees, 34% of the service is provided by them in the UK (Breeze et al. , 2011) , leaving 66% that must be provided by wild insect pollinators.

1.3 There is evidence of recent declines in wild pollinators (Potts et al. , 2010) and indications of parallel declines in wild plants dependent on pollination (Biesmeijer et al. , 2006) , but no evidence of declines in insect-pollinated crop yields (Aizen & Harder, 2009; Breeze et al. , 2011) .

1.4 Much of the evidence for wild pollinator decline is inferred from changes in the recorded occurrence of species of bee, fly, beetle, or wasp (e.g. Biesmeijer et al. , 2006; Cameron et al. , 2011) . These records are generally collected by volunteer participants without following a defined survey protocol. The primary aim of such recording is to produce distribution atlases (Collins & Roy, 2012) , although methods to extract trends in geographic range and frequency from these data are developing (Biesmeijer et al. , 2006; Hill, 2011; Morris, 2010) .

1.5 The direct evidence we have of declines in wild pollinator abundance over time (as opposed to declines in diversity or range) comes largely from long-term data on butterflies (and, to a lesser extent, moths), collected through participatory monitoring schemes with defined survey protocols involving standardised observations repeated regularly over space and time (Conrad et al. , 2006; Fox et al. , 2011; Warren et al. , 2001) . There is some direct evidence for dramatic falls in the relative abundance of long-tongued bumblebee species in Sweden (Bommarco et al. , 2012) . The Bumblebee Conservation Trust has recently started a national bumblebee survey in the UK .

1.6 Current scientific opinion is that pollinator decline is likely to be caused by multiple interacting pressures lowering pollinator health, abundance and diversity, rather than any single threat (Brown & Paxton, 2009; Potts et al. , 2010) . Pesticides are one of these multiple, interacting threats.

2. The need for data on actual exposure


2.1 To assess the magnitude of the threat from pesticides, there is an urgent need for data on the actual exposure of wild pollinators to neonicotinoids , or to multiple pesticides including neonicotinoids, in their natural environment.

2.2 There are data on pesticide residues in nectar and pollen in crop plants (Cresswell, 2011) , and in pollen, honey and wax collected or made by honey bees (Blacquiere et al. , 2012) . Most of these data are not accompanied by data on the usage of the chemicals in the landscapes where the bees foraged.

2.3 I know of no published data on pesticide residues in products collected by free-living wild bees or ingested by other flower-feeding insects such as hoverflies. The foraging behaviour and life histories of flower-feeding insects mean that reported levels of pesticide residue in crop plant nectar and pollen do not equate to actual exposure (Brittain & Potts, 2011) . Most flower-feeding insects are generalists and opportunists. They feed on a range of available resources, including wild plants and crop plants.

3. Defra Project PS2371


31. Defra has commissioned a project (PS2371) to ‘fill identified evidence gaps, including the questions raised about the relevance of recent studies to field conditions’ (Defra, 2012) . This project is described as an ‘edge of field exposure’ study that will take place over a single season. It will presumably use captive-reared colonies of the buff-tailed bumblebee Bombus terrestris . I have not been able to see any detailed methods or plans for the project.

3.2 Whilst the project will undoubtedly provide interesting results, they will probably be limited to one common bumblebee species, in one landscape, in one year. The species, Bombus terrestris , is common and widespread. Its range has not declined, but there are no data on whether its abundance is changing over time. This project should be considered a single case study. It will not provide the evidence required to establish whether, or to what extent, wild pollinator declines are caused by pesticides.

3.3 One potential methodological flaw in the PS2371 study is that buff-tailed bumblebees have been experimentally shown to prefer to forage more than 100 m away from the colony site (Dramstad et al. , 2003) . If the experimental colonies are placed on the edge of 1 ha (100 m x 100 m) fields of experimental oilseed rape, as suggested in the risk assessment guidelines, it is likely that they would choose not to forage in the rape. This species has an estimated foraging range of up to 625 m (Darvill et al. , 2010) . The workers could be foraging anywhere in a 1.3 km diameter circle of landscape around the experimental fields and avoiding the experimental treated rape. It is unclear how this problem will be dealt with in the method.

3.4 This project provides no information about the exposure of wild solitary bees, hoverflies, butterflies and other flower feeders to pesticides.

4. Serious implications for bumblebee colonies


4.1 The existing published evidence about the sublethal effects of neonicotinoids on bumblebees (particularly Gill et al. , 2012; Whitehorn et al. , 2012) show serious implications for bumblebee colonies are possible, if they are being exposed in the wider environment at the levels tested. Effects have been measured on reproductive fitness (85% reduction in new queen production) and colony foraging (69% of workers lost over four weeks when exposed to neonicotinoid and pyrethroid combined). Such effects would be unacceptable.

4.2 Defra's position seems to be that it would not change regulation unless there was unequivocal evidence that serious implications for bee colonies were likely.

4.3 The precautionary principle would suggest a planned phase out or temporary restriction of neonicotinoid use, awaiting further evidence of the likelihood of the demonstrated effects.

4.4 The Chemicals Regulation Directorate's comments reported by Defra (Defra, 2012) suggest that control and treatment groups were fed different diets in the Whitehorn study, with control bees consuming nectar while treated bees had sugar water. This is wrong. Both control and treatment controls were fed sugar water during the two-week experimental phase, then both control and treatment colonies were allowed to forage freely outside.

5. No published evidence on sublethal effects for other wild pollinators


5.1 There is no published evidence about the sublethal effects of field-realistic levels of neonicotinoids on solitary bees or other wild flower-feeding insect groups such as butterflies, moths and hoverflies.

5.2 Emerging evidence from the STEP project ( ), not yet published, is expected to show adverse reproductive impacts on the solitary bee species Osmia bicornis .

6. Lack of transparency in the regulatory process


6.1 There is a distinct lack of transparency about the methods used to make regulatory assessments for individual pesticides. The multi-year/multi-site field trials referred to for thiamethoxam in the Defra document on neonicotinoids (Defra, 2012) are unpublished and apparently not available for scrutiny. Given the challenges of such field scale assessments, due to the foraging range of bees (see point 3.3) and the spatial and temporal variability of landscapes, the methods used are highly pertinent to any assessment of whether or not there is a likely unacceptable influence on non-target species. Why can scientists outside the regulatory process not have access to these studies?

7. Measures to enhance natural pest control


7.1 Alternative non-chemical approaches to pest control in a commercial farming context have not been given enough attention in policy or research. Pest and disease regulation is identified as an ecosystem service, delivered mostly in enclosed farmland and continuing to be highly impacted by the conversion and intensification of natural habitats to farmland (UK NEA, 2011) . As pest regulation is largely delivered by free-living predatory invertebrates, the service is likely to be adversely affected by the use of insecticides and conversely, is likely to be enhanced by reducing insecticide use.

7.2 In France, the primary agricultural producer in Europe, the Ministry of Agriculture and Forestry’s ECOPHYTO2018 Programme aims at a progressive eradication of 53 of the most dangerous chemicals, and a decrease of 50% in the use of pesticides within 10 years (by 2018). By contrast, the UK has no coordinated national effort to reduce pesticide use. Data published by the Food and Environment Research Agency show that overall pesticide application rates rose 6.5% between 2005 and 2010 in the UK, due to greater intensity of treatment per ha on some crops (Breeze et al. , 2012) .

7.3 My team at the University of Cambridge are synthesizing scientific evidence on enhancing natural pest control, as part of a Natural Environment Research Council Knowledge Exchange Programme on Sustainable Food Production ( ). We are working with an international group of advisors, including experts in insect ecology and agronomy.

7.4 So far we have identified 59 different measures that can enhance natural pest control in arable or livestock farming. This list is unpublished, but can be provided on request. We have carried out a literature search using a systematic search protocol (submitted to the journal Environmental Evidence ), and so far identified over 4,000 individual studies that provide evidence for the effectiveness of one or more of the 59 measures. We will begin summarising these studies in plain English in a synopsis of evidence format (see ) early next year, and evidence should be compiled and available for a selection of the measures by summer 2013.


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9 November 2012

Prepared 19th November 2012