Leading industry figures have made a robust response to claims by the University of Sussex's Professor Dave Goulson this month that plants sold in garden centres contain a cocktail of chemicals dangerous to bees.
Goulson's study, "Ornamental plants on sale to the public are a significant source of pesticide residues with implications for the health of pollinating insects", has been accepted for publication in the journal Environmental Pollution. It claims to have found "bee-friendly" plants with traces of insecticide products prohibited by the EU in the plants' pollen. Industry figures say the chemicals cannot have been introduced in the EU and question whether the levels found are dangerous but say the supply chain needs examining, which might give more opportunities to British growers.
After screening of pollen, nectar and leaves from 29 bee-friendly plants on sale in B&Q, Homebase, Aldi and Wyevale, most with RHS "Perfect for Pollinator" logos, Goulson says 70% contained neonicotinoids, sometimes at levels "exceeding those found in treated crops and implicated in bee declines". Goulson also claims that every retailer had plants for sale containing banned neonicotinoids (imidacloprid, thiamethoxam or clothianidin).
The report authors tested the plants for eight insecticides and 16 fungicides "commonly used in ornamental production". They detected neonicotinoid insecticides in more than 70% of the analysed plants. Chlorpyrifos and pyrethroid insecticides were found in 10% and 7% of plants respectively. Boscalid, spiroxamine and DMI fungicides were detected in 40%. The neonicotinoids thiamethoxam, clothianidin and imidacloprid and the organophosphate chlorpyrifos were present in pollen at concentrations between 6.9 and 81ng/g.
"These chemicals are not banned, they are prohibited from use on flowering arable/horticultural crops and for use on ornamental flowers in the year in which they are to flower," says Goulson. "The plants could easily have been treated the previous calendar year since these chemicals are highly persistent."
HTA ornamentals committee chair and Bransford Webbs managing director Geoff Caesar says: "There are a load of banned neonicotinoids and if they are still appearing in compost that's got to go. They must have been used earlier in the supply chain. We can't use banned neonicotinoids and we don't use any. But how it's going to pan out, I don't know. We propagate most of what we grow so we're pretty sure what we've got, but some we buy in as young plants and we rely on those growers."
Dr Julian Little, bee care spokesperson at Bayer, which makes the legal neonicotinoid thiacloprid, points out that clothianidin, for instance, has never been registered in the UK for ornamentals "so in principle it shouldn't be there".
He adds: "No doubt Dave Goulson thinks they mean something significant but I suspect levels are so low that exposure to bees is going to be negligible. I can't account for why some of these (pesticides) are showing. You have to look at how they did their analysis and how carefully they did their analysis."
Bayer has not sold any products containing Imidacloprid into the ornamentals sector since 2014. There are still two products used that contain this pesticide, Imidasect and Couraze, which have a restricted used in ornamentals only under protection. Neither is from Bayer.
Crop Protection Association and Common Sense Gardening Group chair Gary Philpotts says: "It is not surprising that traces of pesticides have been found in these plants. Modern analytical chemistry means that it is possible to find traces of anything pretty much anywhere. However, the key question is whether the level of pesticides found is harmful to pollinators? For example, for thiacloprid, the most prevalent neonicotinoid found in this study, bees would need to consume 21,794g of pollen to reach a lethal dose and this would take the average bee around 2,000 years.
"The reality is that these plants are not exposing bees to pesticides at concentrations that result in harmful effects. Gardeners should not be put off buying plants that are a rich source of forage as a result of this study. In fact, to do so would be counterproductive as gardeners would be removing sources of pollen that bees relish."
Sense of perspective
HTA horticulture head Raoul Curtis-Machin adds: "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.
"We don't know the full story yet about the ages of plants or too much about their sourcing - supply chains are very complex these days. UK growers are doing their best to use pesticides only where necessary and according to the regulations.
"Some of the chemicals found have been out of circulation for a year now, which begs the question how old are the plants and where have they come from, and (about) buying plants from outside the EU. It's similar to the GM issue, looking at the supply chain, how to get it better and tidy up loose ends. From a retailer perspective it's hard to have a transparent supply chain. But it's all sub-lethal doses and they've still not nailed the evidence (about harm to bees)."
Curtis-Machin says Goulson believes any garden planting is better than none for bees and the issue is a "balancing act about what's acceptable and what isn't" and "working towards acceptable levels in ornamentals". He adds that the study "shines a light on the supply chain" rather than being particularly damaging to sales. "We ought to look at growing practises and make them as sustainable as we can. Post-Brexit there might be more UK-grown opportunities."
The RHS and Homebase say they are taking the report "seriously". Wyevale says: "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." Aldi stopped selling bedding grown with neonicotinoids in October 2016 and does not sell plants under RHS Perfect for Pollinators.
NFU senior regulatory affairs adviser Dr Chris Hartfield says the statement in Goulson's conclusion "we are not able to evaluate whether the net effect of planting 'pollinator-friendly' flowers contaminated with pesticides is likely to be positive or negative" is the most important line in the report.
"Planting plants with bee-friendly flowers is clearly a positive for bees. The conclusion makes it very clear that the authors weren't able to balance this positive against any possible harm to say whether or not planting pollinator-friendly plants with pesticide traces was a still a good thing or a bad thing. So basically you have a plethora of organisations asking gardeners to plant flowering plants to help bees, and you have this report that basically concludes that it can't say whether or not traces of pesticides on such plants is a bad thing."
Both thiacloprid and acetamiprid have approval for 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 that a plant will be pest-free.
Direction of traffic
On pesticide use generally, Little says: "At European level there is a big concern about the direction of traffic. I coined the expression that the European model for agriculture is one of a drift towards 'museum agriculture' and everyone else in the world looks at our system and doesn't understand what they're doing and why they're doing it.
"Brexit is a huge issue for UK farmers and growers but there will also be opportunities that will have to be grasped. The UK Government is not going to give the same levels of subsidies as CAP so you have to look at competitiveness and maybe access to those sorts of products that may not be accessible to European counterparts and be more competitive in a post-Brexit world.
"The decision by B&Q to phase out things like thiacloprid strikes me as bizarre. It's extremely safe to bees. That tells us again the direction of traffic. If in the ornamental sector people want affordable plants without crop-protection pesticides it will become a lot more difficult for growers. We'll either end up with poorer plants and gardens or we need to fundamentally look at the drift and go 'this doesn't make sense' and for the Government to make a more pragmatic response to calls for bans."