Wild Poppies flowering on edge of a wheat field in Essex. Beautiful - what about the bees? Photo: ukgardenphotos via Flickr (CC BY-NC-ND).
Bee-killer pesticides concentrate in wild flower pollen
15th October 2015
Wild flower margins around arable fields can funnel deadly pesticides into the bees, wild pollinators and other insects they are intended to benefit, writes Oliver Tickell. Neonic pesticides are often far more concentrated in the wild flowers than in the crop itself.
The research shows that eye wateringly high concentrations of deadly insecticides have been frequent in hedgerow plants and it seems highly likely that this has been damaging the populations of hundreds of wild insects.
A new study shows that neonicotinoid pesticides are found at higher levels in wild flowers and pollen around a field of neonic-treated plants, than in the crop itself.
Oilseed rape flowers in the neonicotinoid treated crop contained an average of 3ppb of neonic pesticide, compared to 15ppb in the adjacent wild flowers.
The researchers from the University of Sussex also found that the neonics were concentrated in the pollen of wild flowers including Hogweed and Poppy, recording levels as high as 86ppb and 64ppb respectively.
As a result 97% of the pollen-borne neonicotinoids carried into honeybee hives came from wild flowers. Honeybees examined in the study were also collecting enough neonicotinoids to damage their productivity and reproduction rate.
At these levels the neonics can also harm wild pollinators and other caterpillars and bugs living near arable fields.
The study, 'Neonicotinoid Residues In Wildflowers, A Potential Route Of Chronic Exposure For Bees' has just been accepted by the journal Environmental Science & Technology.
Exposure far greater than previously supposed
"Current focus on exposure to pesticides via the crop overlooks an important factor", the authors write. "Throughout spring and summer, mixtures of neonicotinoids are also found in the pollen and nectar of wildflowers growing in arable field margins, at concentrations that are sometimes even higher than those found in the crop.
"Indeed the large majority (97%) of neonicotinoids brought back in pollen to honey bee hives in arable landscapes was from wildflowers, not crops. Both previous and ongoing field studies have been based on the premise that exposure to neonicotinoids would only occur during the blooming period of flowering crops and that it may be diluted by bees also foraging on untreated wildflowers."
Planting flower rich field margins has been promoted by pesticide companies and the Government as a solution to the pollinator crisis. The 'solution' has been widely implemented by farmers who receive EU-funded 'agri-environment' support for leaving broad crop-free margins for wild flowers.
But as the authors conclude, "exposure is likely to be higher and more prolonged than currently recognized due to widespread contamination of wild plants growing near treated crops."
The study does not examine how the pesticide gets into the wild flowers, however it is likely to be through the movement of dust and neonic residues through air, soil and water. Where the pesticide is sprayed it will also drift into field margins.
Other studies confirm the dangers
"For many years Buglife has been raising concerns that neonicotinoids are likely to be following a pathway through margins and hedgerows into herbivores such as butterflies, moths, sawflies and bugs", said Matt Shardlow, Chief Executive of Buglife, the insect conservation charity.
"Earlier this year a paper was published linking the decline of Monarch butterflies in the USA to neonicotinoids in field margins. The new University of Sussex research makes it clear that eye-wateringly high concentrations of deadly insecticides have been frequent in hedgerow plants in the UK and it seems highly likely that this has been damaging the populations of hundreds of wild insects."
This study comes just a week after a Canadian study found huge levels of neonicotinoids in the surface dust of arable fields and evidence that this dust blows into adjoining fields contaminating them and putting surface living predatory beetles at risk.
Last December work by Plymouth University showed that bumblebees preferred roadside verges to field margins. Now this study may explain why that is the case - because the margins can be heavily contaminated with insecticides.
This July work by Sussex University and the Game and Wildlife Conservation Trust showed that field verges helped bumblebees, but were of very limited value to the hundreds of species of solitary bees and other pollinators.
"While flower-rich arable margins doubtlessly provide some succour to bumblebees and honeybees, they do not help solitary bees, or provide nesting habitats", concluded Shardlow. "Nor do they help herbivores such as moths, leaf beetles and bugs as the habitat is often ploughed or sprayed off with herbicides before they complete their lifecycle.
"The restoration of wildflower meadows to create corridors of quality pollinator habitats, as proposed and guided by the national B-Lines scheme remains the strategy most likely to halt and reverse the loss of pollinators and grassland biodiversity."
Oliver Tickell edits The Ecologist.
The paper: 'Neonicotinoid Residues In Wildflowers, A Potential Route Of Chronic Exposure For Bees' by Cristina Botías, Arthur David, Julia Horwood, Alaa Abdul-Sada, Elizabeth Nicholls, Elizabeth M Hill, and Dave Goulson is published in Environmental Science & Technology.
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