Study mapping pesticide use in garden plants claims to have found traces of unauthorised neonicotinoids

A study from University of Sussex's Professor Dave Goulson, which has been accepted for publication in the journal Environmental Pollution, claims to have found 'bee-friendly' plants with traces of insecticide products banned by the EU, in pollen.

Goulson said: "We screened pollen, nectar and leaves from 29 different 'bee-friendly' plants on sale in retail outlets (B&Q, Homebase, Aldi, Wyevale). Most plants had RHS "Perfect for Pollinator" logos, and all are on the RHS list of plants that are good for pollinators.

"All but one plant contained pesticides, and one plant contained 10 different pesticides. 70% contained neonicotinoids, sometimes at levels exceeding those found in treated crops, and implicated in bee declines. Every retailer sold plants containing the 'banned' neonicotinoids (imidacloprid, thiamethoxam or clothianidin)."

Some neonicotinoids including thiacloprid are permitted for use in EU countries.

Sussex University's Dr Francis Ratnieks released a similar report earlier in 2017.

Goulson has been working in the project since 2016.

The RHS and Homebase said they were taking the report "seriously". Wyevale Garden Centres said: "We fully support the RHS movement to promote pollination through planting, and along with the rest of the industry, we are working towards ensuring we are following best practice in this matter."

B&Q told HW in April they are stopping selling plants grown with any neonicotinoids.  Aldi stopped selling bedding grown with neonicotinoids in October 2016 and does not sell plants under RHS Perfect for Pollinators.

HTA horticulture head Raoul Curtis-Machin said: "The findings suggested in this report will be of serious concern to the industry, and we will address them in more depth in due course. We also need to keep a sense of perspective with the neonicotinoids debate, and not forget that flowering plants in gardens provide a very valuable source of food for bees."

The report's authors tested 29 different ‘bee-friendly' plants for 8 insecticides and 16 fungicides commonly used in ornamental production. Only two plants (a Narcissus and a Salvia variety) did not contain any pesticide and 23 plants contained more than one pesticide, with some species containing mixtures of 7 (Ageratum houstonianum) and 10 (Erica carnea) different agrochemicals.

Neonicotinoid insecticides were detected in more than 70% of the analysed plants, and chlorpyrifos and pyrethroid insecticides were found in 10% and 7% of plants respectively.

Boscalid, spiroxamine and DMI fungicides were detected in 40% of plants. Pollen samples collected from 18 different plants contained a total of 13 different pesticides. Systemic compounds were detected in pollen samples at similar concentrations to those in leaves. "However, some contact (chlorpyrifos) and localised penetrant pesticides (iprodione, pyroclastrobin and prochloraz) were also detected in pollen, likely arising from direct contamination during spraying," said the report.

The neonicotinoids thiamethoxam, clothianidin and imidacloprid and the organophosphate chlorpyrifos were present in pollen at concentrations between 6.9 and 81 ng/g.

Both thiacloprid and acetamiprid have approval to use on ornamentals and have not been cited as being dangerous to bees in agriculture and are therefore not subject to the ban. Growers use the approved neonicotinoids on pests such as aphids, whitefly and vine weevil. Without using neonicotinoids it becomes increasingly difficult for growers to guarantee a plant will be pest-free.

Dr Julian Little, bee care spokesperson at Bayer, which makes thiacloprid, told HW recently: "The science and research shows that thiacloprid is so safe to bees that it can be used on open flowering oilseed rape. Plant growers have used this product safely for many years to control pests that otherwise cause serious damage to young seedlings and plants."

The authors of the report, titled 'Ornamental plants on sale to the public are a significant source of pesticide residues with implications for the health of pollinating insects' are A Lentola, A David, A. Abdul-Sada, A Tapparo, D Goulson and E M Hill of the Department of Chemical Sciences, University of Padova, and School of Life Sciences, Sussex University.

#The HTA has issued a position statement and guidance for garden centres on neonicotinoids:

1.1 There are around 250 bee species in the UK, and in addition to their contribution of £16 million to honey producers, they make an invaluable contribution to our £100 billion food industry. Peer-reviewed scientific evidence suggests that the current decline in bee numbers is due to several factors: parasites such as the varroa mite; habitat loss; fungal and viral diseases.

1.2 Since the 1990s, there has been ongoing debate about the effect of the neonicotinoids group of plant protection products on bees. The UK Government maintains stringent controls and processes over the approval and use of these products. Their use in ornamental plant production accounts for 0.03% of their total use in UK agriculture and horticulture, according to the last Government data survey carried out in 2009.

1.3 Gardens and flowering garden plants play a crucial role in supporting bees and other pollinating insects. There are fewer and fewer flowers available in the countryside for pollinators, and therefore flowering plants in our gardens represent a vital food source. The industry works closely with the Government and other stakeholders on promoting and delivering the National Pollinator Strategy.

1.4 A limited number of neonicotinoids are used by growers to produce pest-free plants. Out of the nine products classed as neonicotinoids, there are only two in regular use in ornamental horticulture (Thiacloprid and Acetamaprid), with a third used sparingly for vine weevil control. These products were not part of the EU restrictions that were implemented on three neonicotinoid active ingredients in 2013. The scientific evidence recognised at regulatory body and government level does not confirm that these neonicotinoids cause direct harm to bees, when used as directed by the manufacturer.

1.5 These products are used when natural methods are deemed to be ineffective to meet pest and disease control needs. Research is ongoing into alternative methods, but growers currently face a very limited range of controls for year-round vine weevil control. Ornamental plant production falls within the official ‘Minor Uses’ category because the amount of products applied represents a minor use compared to other crops.

1.6 The EU and UK Government have dictated which neonicotinoids are allowed and how they can be used, and ornamentals growers have reacted immediately and voluntarily to comply with any changes as they have been introduced. The industry works closely with government bodies and other stakeholders to uphold high standards of environmental management and the use of plant protection products.

1.7 A recent report featured in the press set out to establish the presence and levels of a range of plant protection products found in and on ornamental plants for sale through garden centres. We take the report seriously and will analyse the findings when the full paper is published. If necessary we will modify our advice to growers accordingly, bearing in mind the limited range of plant protection products that ‘minor uses’ crops have available to them.

1.8 As we expected, a range of products were found at low levels, confirming that growers abide by the EU regulations, including the edible crop harvest interval for a non-edible plant.

It should be pointed out that the testing was carried out 12 months ago and several of the substances found are no longer approved or available to growers. It also appears to have been carried out in a very restricted area of the country. Clothianidin has no approval, nor is it likely to have been used on ornamentals. It is only available as a cereal seed dressing and not as a foliar spray or substrate drench.

1.9 The presence of this active substance on an ornamental plant would suggest that contamination has occurred, either in the sampling process or by some bird or insect vector during the sale or testing retention period. Chlorpyrifos is most likely to have been used as a substrate drench against Vine Weevil larva, and it is no longer approved or available. Both neonicotinoids thiamethoxam and imidacloprid have had approvals in the past, which might explain their presence. No age of the plants tested has been given, however, nor whether they were UK-grown or imported, and we look forward to reading about this in more detail.


Annex: Summary points to aid staff with any questions which may come from customers

  • Gardens and flowering garden plants play a crucial role in supporting bees and other pollinating insects;
  • There are really only two neonicotinoids which are currently used widely in UK ornamental plant production (Thiacloprid and Acetamaprid), and a third which is used sparingly as the only current year-round effective treatment to control vine weevil;
  • In general, growers use chemicals as a last resort, to ensure pest-free plants, but they currently have a very limited choice in controlling some pests such as vine weevil;
  • The industry works closely with the Government and other stakeholders on promoting and delivering the National Pollinator Strategy;
  • The industry also works closely with government bodies and other stakeholders to uphold high standards of environmental management and the responsible use of plant protection products;
  • Traces of these products found in plants tested recently were at low levels, confirming that growers follow strict regulatory guidelines in their use, including the edible crop harvest interval for a non-edible plant. Research is ongoing into alternative treatments to chemicals;
  • There is no danger to human health from the responsible use of neonicotinoids on plants, according to label instructions;
  • Customers should always only use plant protection products according to label instructions.

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