Tag Archives: dave goulson

Perfect poisons for pollinators – available from your local garden centre

We try to make our garden welcoming for bees by growing flowers that provide pollen and nectar throughout the season. We also have some unkempt areas they might want to nest in and we don’t use any pesticides. I enjoy watching the bees foraging on the flowers as they come in to bloom and currently a large cotoneaster bush is full of small bumblebees buzzing loudly as they feed in the sunshine. It’s been very exciting this year to see bumblebees and solitary bees nesting in the dry-stone walls around the garden.

When we need new plants or compost, there is one local garden centre we use. It has a good range of healthy-looking plants and a very nice tearoom! In early spring, it’s also an excellent place to watch one of my favourite bees, the hairy-footed flower bee (Anthophora plumipes), whizzing about in the greenhouses full of flowers. Earlier this year, on a sunny Sunday afternoon in late March, I noticed that these Anthophora had set up nests in the old brick wall of one of the garden centre’s buildings.

Bee 4
A hairy-footed flower bee foraging on plants within the garden centre


About a year ago, I saw a crowd funding request from the well-known bee-defender and researcher, Dave Goulson from the University of Sussex. He wanted the money to test whether plants sold in garden centres in the UK and labelled as “bee-friendly” actually contained bee-toxic pesticides, applied during production of the plants. I remember being quite shocked to read about this possibility – could I have been buying plants to help the bees that were in fact laced with bee-toxic chemicals?

I wanted to find out more so I got in touch with our favourite garden centre and asked whether they were using neonicotinoid insecticides on their plants. They reassured me that they were not. So far so good. I then asked if their suppliers used neonicotinoids in the compost on the plants they sold. The reply came back “I’m afraid I can’t answer that question without phoning every supplier. Also a few companies we deal with import some of their stock from other European countries. I’m happy to ask my local nurseries when I’m speaking to them.” That’s the last I heard.

Dave Goulson got his money and went ahead with the analyses. The results of his tests have just been published and they don’t make happy reading;  here is a link to his blog on the topic. He and his colleagues bought 29 pots of flowering plants from well-known garden centres around Brighton (Wyevale, Aldi, B & Q, Homebase). Many were labelled “bee-friendly” and some had the Royal Horticultural Society endorsement “Perfect for Pollinators”.

They analysed a range of pesticides in leaves and pollen from the plants and found that most of the plants contained a cocktail of insecticides and fungicides. In the leaf analysis, only 2 of the 29 plants contained no pesticides. 76% contained one or more insecticide and 38 % contained two or more. 70% of the leaf samples analysed positive for neonicotinoid insecticides, well known for their toxic effects on bees. In the pollen analysis, neonicotinoids were found at levels known to cause harm to bees. So much for “Perfect for Pollinators”.

As a result of his work, B & Q announced that from February 2018 their plants would be neonicotinoid-free. Aldi revealed that they had stopped using neonicotinoids in October 2016, a few months after Goulson’s analyses took place. Neither B & Q nor Aldi  addressed the other chemicals found in the Sussex analysis.

The Horticultural Trades Association issued a statement that I believe is both silly and cynical, basically rubbishing Goulson’s analysis. You can read Dave Goulson’s rebuttal here.

So, it really is true that when we buy plants to help bees in our gardens from garden centres, we may be unwittingly exposing the bees to harmful chemicals, despite the “bee-friendly” labels. Also, any insect that nips into a garden centre for a feed, especially early in the season when garden centres have an abundance of flowers, may be getting a hit of insecticide at the same time.

So, what do we do if we want to have a bee-friendly garden?

Dave Goulson recommends the following course of action: if you must buy plants, buy from an organic garden centre or, failing that, go to B & Q or Aldi. Better still, grow from seed or swap plants with friends and neighbours.

One point that has not been discussed so far concerns potential effects on humans of these pesticides found in garden centre plants. Earlier this year, I bought some fruit bushes from the garden centre and these now have a nice crop of plump berries. If these plants have been treated with pesticides, and of course I don’t know if they have, then the fruit will presumably also contain these pesticides. This possibility makes me very angry. I grow fruit in our garden so that we can eat chemical free, fresh, good quality produce. I don’t want to ingest insecticides and fungicides with poorly defined toxic effects on humans.

The featured image shows a hairy-footed fower bee feeding from plants in a lane adjacent to the garden centre

Bees and neonicotinoids – another twist in the tale.

To the agrochemical companies and to many farmers they are essential tools ensuring efficient crop production. To environmentalists and to many bee scientists they are dangerous chemicals contributing to declining bee populations. I am talking, of course, about the neonicotinoid insecticides widely used in this country to control insect pests.

Last week two papers were published on-line in the journal Nature emphasising the dangers posed by these chemicals.

One paper, from a team at Newcastle University, investigated whether honeybees and bumblebees showed any preference (positive or negative) for food containing neonicotinoids; there had been suggestions that bees might avoid neonicotinoid-treated crops in the field. The new lab-based work showed that, when offered a choice, bees preferred to eat sucrose solution (nectar) containing neonicotinoids (imidacloprid or thiamethoxam) rather than control sucrose solution. If this occurs in the field then bees may forage preferentially on crops containing chemicals toxic to their health and inadvertently bring back these toxins to their nests.

The second paper, from scientists at Lund University in Sweden, showed that the neonicotinoid clothianidin, when used in the field, damaged wild bee (bumblebee and solitary bee) populations but was without effect on honeybees. I want to focus on this paper as it is the first controlled study of the effects of a neonicotinoid on honeybees, bumblebees and solitary bees under field conditions. Let’s start by looking at the background.

Three years is a long time in science


Back in 2012, two studies were published showing that neonicotinoids, even when they didn’t kill bees, could affect bee behaviour in a way that impaired survival of honeybee and bumblebee colonies. The findings showed that these chemicals could contribute to a decline in the numbers of bees and other pollinators. These observations had a big effect on policy and indirectly contributed to the current partial ban on the use of three neonicotinoids in Europe.

One of the papers was from Dave Goulson’s lab, then at Stirling, and found that even at the low doses typically encountered on treated crops in the field, neonicotinoids substantially reduced the number of queens produced by bumblebee colonies, so impairing survival. In Goulson’s study, bumblebees were treated with neonicotinoids in the lab before being allowed to fly freely. This is called a semi-field design and some have suggested that the findings cannot be extrapolated to the real world. The levels of neonicotinoids have also been criticised although these were very carefully thought through.

There was considerable media interest in this work, nicely described in Goulson’s latest book (A Buzz in the Meadow) and the UK Food and Environment Agency (FERA) labs in York hastily set up a preliminary field trial to examine the problem. During the spring and summer of 2012 they studied three fields of oil seed rape, one treated with the neonicotinoid, imidacloprid, another treated with the neonicotinoid, clothianidin and a third untreated field to act as a control. Bumblebee (Bombus terrestris) nests were placed by each field and the occupants were left to fly freely and build their colonies. Extensive analyses were performed including colony growth, the pollen collected by the bees and pesticide residues detected in pollen and nectar.

Superficially this sounds like a rigorous study (free flying bees, compare neonicotinoid-treated with control, plenty of analyses and so on) and it should have given an indication of the effect of neonicotinoids under real-world field conditions. The success of the trial depended on the bees foraging on the crop near their nests so there should have been clothianidin-exposed colonies, imidacloprid-exposed colonies and neonicotinoid-free controls. Unfortunately the bees had other ideas; they largely ignored the flowering oil seed rape by their nests, foraging further away and returning with pollen from crops treated with another neonicotinoid, thiamethoxam. This completely negated the original design so that, in my view, no valid conclusions can be drawn from the study, despite official pronouncements.


The new Swedish study

The FERA work was a valiant but flawed attempt to study the effects of neonicotinoids on bumblebees under field conditions and it was clear that a properly conceived field trial was required. The ambitious new study from Lund University mostly fills that void.

The Lund team selected 16 landscapes surrounding spring-sown oil seed rape fields in different parts of southern Sweden in 2013. The landscapes were divided in to 8 pairs on the basis of the nature of the surrounding countryside and for each pair one was sown with seed treated with the neonicotinoid, clothianidin and the other was sown without neonicotinoid, to act as a control. All seed also contained a fungicide. The neonicotinoid-treated seed also contained a pyrethroid to protect plant roots but there was no evidence that the bees came in to contact with this chemical.

Honeybee hives, bumblebee (Bombus terrestris) colonies and solitary bee (Osmia bicornis) cocoons were placed by each field during the flowering season and their progress was followed. Additionally, the numbers of free flying wild bees (bumblebee and solitary bee) were assessed at each field during the flowering season. Pollen brought back by bees was analysed for flower type and for pesticide residues. The study was large enough to allow statistical analyses to be performed so that valid conclusions could be drawn although the design was unable to detect effects smaller than 20%.

Unlike the FERA study, bees did forage on the oil seed rape adjacent to their colony based on pollen analysis, although this was not an exclusive choice. Bees near treated fields brought back pollen and nectar containing clothianidin whereas those near untreated fields did not. The study design seemed to have been successful and the results were clear:

1. Honeybee hives behaved similarly by treated and untreated fields; there was no effect of the pesticide on colony strength. This is good news for honeybees and for beekeepers and agrees with a 2014 field study from Canada also using clothianidin.

2. Bumblebee colony growth and reproduction were reduced near treated fields. This agrees with earlier semi-field studies so that it is now difficult to avoid the conclusion that agricultural use of neonicotinoids has damaging effects on bumblebees.

3. Whereas solitary bees placed by untreated fields emerged from cocoons and built new nests, this did not occur for cocoons situated near treated fields, possibly because of navigational problems caused by insecticide exposure.

4. The number of free-flying wild bees was reduced by about 50% at the treated fields.

The implications of the new Swedish study

Honeybees were not affected by foraging from a neonicotinoid-treated crop whereas wild bees (bumblebees and solitary bees) suffered reductions in numbers and reproductive ability. Wild bees are, therefore, more sensitive to neonicotinoids than honeybees. This may be because, as James Cresswell at Exeter has shown, honeybees break down neonicotinoids more quickly than bumblebees so that honeybees experience lower doses.

The effect of the neonicotinoid on wild bees is an important result for several reasons. Wild bees are important pollinators, contributing more than half of the “pollination service” required for crops. Crop yield and quality will suffer if these insects are lost so we need to look after them and that may need to include rethinking use of pesticides.

The differential sensitivity of bee types to neonicotinoids shows that environmental risk assessment of new and existing insecticides, typically performed in short term lethal studies on honeybees, is inadequate to determine long term effects on different bee types in the field.

These new data will add to the pressure to extend the European moratorium on the use of three neonicotinoids as seed dressings after the initial two year period ends in December. There is, however, concern that if neonicotinoids are not available then farmers will use older insecticides that may be more dangerous for bees. Perhaps farmers should rethink their use of pesticides and return to a “treat when required” policy rather than using neonicotinoids prophylactically.

When the three neonicotinoids were temporarily banned in 2013, farmers claimed that the yields of crops would be drastically reduced. It is interesting that in the first season when crops were grown from untreated seed in the EU, the yields actually increased. Perhaps we should rethink the use of chemicals more generally in modern farming.

Winter-active bumblebees in a Devon seaside garden

It was a sunny Sunday morning in January last year and we were walking through public gardens at Roundham Head in Paignton, South Devon. Passing a bank of flowering rosemary, we spotted a bumblebee. Surprising? Well yes, bumblebees are supposed to be hibernating in January, aren’t they?

Worker bumblebee on veronica in winter
Worker bumblebee on Hebe (January 4th 2015)


Fast forward 12 months to January 2015 and we are passing through these same gardens. As we enjoy the sunshine we notice another bumblebee, feeding on a very smart looking purple Hebe. This time we take a few photos before the insect flies off and we confirm that it’s a worker bumblebee with loaded pollen baskets.

I was very intrigued by these observations and felt compelled to find out more, but first I need to tell you about the gardens as they are a bit special.

Roundham Head

Roundham Head
Roundham Head from the southern side showing the Cliff Gardens above the esplanade with the red cliffs on the far right.


The popular seaside holiday resort of Paignton is enclosed by urban sprawl and Roundham Head is a surprising botanical oasis in this part of South Devon. To the North of the headland is Paignton harbour with its many tempting summer treats (wildlife and angling cruises, Molly Malone’s seafood stall and so on), all sadly closed at this time of year. To the South is Goodrington Sands, fine for a pleasant summer’s dip but, in winter, a dog and doggy walker’s paradise. The headland itself is surrounded by steep red cliffs and is grass-topped with a fine stand of pine trees offering Mediterranean views across the Bay to Torquay.

Pine trees at Roundham Head, Paignton
Pine trees at Roundham Head – Mediterranean view?


Goodrington Sands
The view from the gardens towards Goodrington Sands


The cliffs on the southern side are where we find the Cliff Gardens (sometimes called Paradise Gardens). A maze of flower beds and zigzag paths ascend and descend the cliffs and there is an occasional secluded seat for those who wish to contemplate the sea or simply rest. The Gardens themselves seem to enjoy a very mild microclimate. Many of the borders are protected from the wind and for much of the day, the sun, when it is out, warms the soil. The Gardens are home to tender, sub-tropical plants and there are flowers throughout the year. The predominant colour in January is yellow from the scorpion vetch (Coronilla valentina, a native of the Mediterranean ) which thrives here.

scorpion vetch
Scorpion Vetch


My visits to the Cliff Gardens

Five days after the most recent sighting, I am back in the gardens with my camera, looking for bumblebees and getting a few odd looks from passers-by. I had scoured the forecasts on the Met Office web site and the weather today was predicted to be sunny and mild (12oC, good for bees), although rather gusty and getting windier (not so good for bees). It is a bit of a gamble but I decide to risk a visit.

worker with pollen
Worker bumblebee on rosemary (January 9th 2015)


When I reach the Gardens I take the first path, half left downhill, where there is a huge bank of rosemary facing in to the sunshine, enveloping the border and the wall below. It’s a mass of small blue flowers and I immediately see a worker bumblebee on the blooms, its pollen baskets laden. It’s either a buff-tailed (Bombus terrestris) or white-tailed (Bombus lucorum); the workers of both species look similar. I zigzag up and down the paths and don’t see any others until I come across a large island border just below the top of the cliffs. This is filled with flowering rosemary, some tired-looking bergenia, and more scorpion vetch. There are two or three queens here, definitely Bombus terrestris based on their buff-tails, feeding from the bergenia and rosemary flowers. They don’t use the vetch. It’s quite gusty but they are very determined and forage despite the wind. I feel sorry for them: one gets blown off a flower stem another seems to shelter for a while but she could be warming up. Eventually I give up as the wind is too strong.

Queen bumblebee in winter
Buff-tailed queen on rosemary – by comparison with my hand she is about 2.5 cm long (January 9th 2015)


Bumblebee queen on bergenia
Bumblebee queen on Bergenia (January 9th 2015)


Despite the weather, it was worth the visit but I now have many questions. How many bees and how many colonies? Are they all buff-tailed? Where are the nests? Why is there a mixture of workers and queens?


So, two weeks later, the weather again looks possible and I am back. The temperature today is ~9oC, a mixture of sunshine and cloud with a light wind. There was frost the night before in Totnes and, although it probably didn’t frost in Paignton, I wonder how the lower temperatures will have affected the bumblebees.

Bumblebee worker on Grevillea
Bumblebee worker on Grevillea (January 23rd 2015)


In fact all seems to be well. I see workers with pollen on the hanging rosemary, on the hebe and on a shrub covered with unusual spiral-shaped red flowers that I identify later as Grevillea, a native of Australia. Some of these workers fly at me as if to shoo me away; perhaps they feel threatened. At the island border I see a worker and several queens feeding off the rosemary. At one point, a queen flies to the ground where she wanders about apparently looking for something. There are no bumblebees on the bergenia today but, astonishingly, I see a red admiral butterfly on this plant.

bumblebee queen on rosemary
Buff-tailed queen approaching rosemary (January 23rd 2015)


Red Admiral on bergenia
Red admiral (a little tattered) on Bergenia (January 23rd 2015)


I don’t think I learnt very much from this visit except that this is a very mild spot with plenty of bee forage even in midwinter.

So, I decide to visit again just under two weeks later on another sunny day. In Totnes the air is very cold (~5oC) but, when I get to Roundham Head, the sun is shining directly on the Gardens, it feels quite warm and there is little or no wind. My experience today is different: I don’t make any definite sightings of queens but I do see several workers and with one exception these are all feeding on rosemary. The workers differ considerably in size but that’s a common observation. They all look in very good condition; their wings are not frayed so they are relatively young. While I stand near the Grevillea, a large bee, probably a queen, flies at me, does a few circuits around my head and then flies off. I get the impression I am being warned but perhaps I am overreacting!

Bumblebee worker on rosemary 2
Bumblebee worker approaching rosemary (February 4th 2015). If you click on the photo you should be able to see the brown band before the white tail (typical of B. terrestris)


Bumblebee worker on rosemary 3
Bumblebee worker on rosemary (February 4th 2015) – note the brown band before the white tail (typical of B. terrestris). I am not sure where this one found the yellow pollen?


Later, when I have a good look at the photos of the workers I notice that they have a narrow brown band just before the white tail. This is typical of buff-tailed bumblebees and is not seen on white-tailed workers so it is likely that the active nests are buff-tailed (Bombus terrestris).

What does it all mean?

Over a period of about four weeks in the middle of winter, I have been able to see buff-tailed bumblebee queens and workers quite easily at this location. I get the impression, however, that there are actually not very many about: perhaps four queens and eight workers?

The presence of foraging workers as early as January 4th indicates an active nest. I have no idea about the site of the nest but I assume there is a queen, tending larvae and being fed by the workers. The nest was probably established in the last few months of 2014.

At this time of year, bumblebees typically hibernate but since the 1990s there have been reports of winter-active colonies of mainly buff-tailed bumblebees, largely confined to the southern part of the UK. Speculation has been rife as to what is causing this change in behaviour. Some suggest it is linked to warmer winters associated with climate change. This can’t be the whole story as, according to Dave Goulson, bumblebees in Brittany do not exhibit the same winter activity. The magic ingredient may be the availability of winter forage in the UK linked to the British passion for gardening and planting winter-flowering shrubs.

The sub species of Bombus terrestris found in some parts of continental Europe can also have two nesting periods a year, when climate is suitable and winter forage is available. A litter is produced across spring and summer and fertilised queens find suitable places to hibernate for 2-3 months before emerging in late September to set up new colonies across the winter. The Roundham Head colonies probably arise from fertilised queens produced during summer 2014 who emerged after a few months rest to set up winter nests. The microclimate and the abundant local forage make this activity possible.

There has been speculation that the continental sub species of Bombus terrestris, imported for pollinating vegetable crops, may be escaping and establishing itself in the UK. Given that this sub species sometimes produces two generations, it is possible that these continental bumblebees could be the winter-active bumblebees seen in the UK. The Roundham Head colonies, however, have the physical characteristics of the British sub species so they cannot be foreign escapees.

What about the queens that I saw? Here it all becomes rather uncertain. They could be founding queens from active autumn/winter 2014 nests coming out for a feed or they could be new queens generated by these nests. Alternatively, they could be queens from summer 2014 nests emerging from hibernation on a warm day. What might happen to these summer 2014 queens is also a bit unclear. They might set up new nests if the weather stays warm. Perhaps if the weather turns cold they return to hibernation after feeding but, it is not known if this actually occurs.

So, more questions than answers, but there definitely are active winter nests at this favourable seaside spot. It’s been fascinating and great fun to observe these bees and I shall continue watching over the next few months to see what else I can learn.

I should like to thank Dave Goulson (University of Sussex) and Tom Ings (Anglia Ruskin University) for helpful comments.

Goodrington Sands
Another view over Goodrington Sands at low tide