Pesticides and honeybees

Here are some details of the science that has already been done on pesticides and honeybees. Studies on normal full colonies of honeybees, not a few bees in cages in the lab or small test colonies in containment.

Do agricultural pesticides in normal use harm bees? I used to think so. However the UK regulators have done their job properly and the pesticides in use are not associated with bee problems. I can’t find any studies of real bee colonies that show any deleterious effects of pesticides in normal use on honeybees, and there have been several that have tried to make that association. Randy Oliver has also looked and not found any studies that convincingly show harm to honeybees, and he plans to publish his review in the American Bee Journal.

If anyone is aware of other significant research in the area of field studies of colony health in relation to farm pesticides, miticides and colony health that adds significantly to those cited here, please do let me know and I will add it to this web page.  This resource was to be associated with an article I wrote for the April Scottish Beekeeper but which was held over until the May issue.

It should be obvious that any new scientific study has to take into account what the existing science has already done. You cannot build a sensible research programme without considering carefully what has been done before. Neither is there any point researching something where casual observations say that there is nothing worth researching. Any good science should erect a plausible hypothesis based on some kind of assessment of what is actually happening. Are colonies losing unusual numbers of bees when the oilseed rape comes into flower? Are colonies doing that when beekeepers treat with one of the approved miticides? Not in my experience, nor in that of any experienced beekeeper I’ve spoken to. So let’s have a look at what science already tells us about working colonies and exposure to farm and beekeeper pesticides.

1.  Penn State research

Various studies including one lead by Maryann Frazier which showed widespread contamination in US colonies, particularly of the miticides coumaphos (not approved for use in the UK), fluvalinate (also a Varroaicide) and chlorpyriphos (an insecticide used by commercial beekeepers in the States to kill fire ants around their hives to prevent problems with the inter-state movement of hives).  The study from the group that looked at the association between pesticides, miticides, pathogen status and colony health was this one:

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006481

'Of 61 quantified variables (including adult bee physiology, pathogen loads, and pesticide levels), no single measure emerged as a most-likely cause of CCD. Bees in CCD colonies had higher pathogen loads and were co-infected with a greater number of pathogens than control populations, suggesting either an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Levels of the synthetic acaricide coumaphos (used by beekeepers to control the parasitic mite Varroa destructor) were higher in control colonies than CCD-affected colonies.'

and

'None of the pesticides detected in more than 20% of the samples in a given matrix was more prevalent in CCD apiaries than in control apiaries (Table 9). There were, however, higher levels of coumaphos in the wax of control apiaries than was detected in CCD apiaries (Wilcoxon rank sum test, P = 0.05, Table 9).'

So, coumaphos *protects* against CCD rather than causes it, presumably because its aggressive use controlled Varroa.  Many variables were determined by professional researchers and the pathogen loads were the important ones.

2.  More Penn State research.

'Entombed pollen'.

This was mentioned in the Guardian recently:

http://www.guardian.co.uk/environment/2011/apr/04/honeybees-entomb-hives?CMP=twt_fd

and in this paper by the Penn State group and collaborators:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJV-4W1BVD7-1&_user=10&_coverDate=06%2F30%2F2009&_rdoc=1&_fmt=high&_orig=gateway&_origin=gateway&_sort=d&_docanchor=&view=c&_searchStrId=1705002884&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4bbf488bec81479af72d519f5930aa78&searchtype=a

The entombed pollen contains high levels of the fungicide chlorothalonil, a pesticide sometimes used in a dust formulation on the kinds of crops US commercial stocks may forage on.  The abstract says amongst other things 'There appears to be a lack of microbial agents in the pollen, and larvae and adult bees do not have an increased rate of mortality when they are fed diets supplemented with entombed pollen in vitro, suggesting that the pollen itself is not directly responsible for increased colony mortality.'

So this does suggest that US colonies are exposed to alarming levels of pesticides and that affects the usage of contaminated pollen.  However there is no suggestion that the toxicity was directly causing colony collapse.

3.  Recent German research.

This was circulated recently to some on the SBA Executive from a source in Germany.  The paper is available here:

http://www.sbai.org.uk/pesticides/Genersch_The German_Bee_Monitoring_Project.pdf

This was a large project monitoring more than 1200 colonies in 120 apiaries.  As in most of these field-based projects the effort was directed at professional field work that collected a lot of data on a variety of factors in a way that was independent, ie it didn't make assumptions about the cause but looked at all possible factors.  Here is a quote from the abstract:

'Bee samples were collected twice a year to analyze various pathogenic factors
including the ectoparasitic mite Varroa destructor, fungi (Nosema spec.,
Ascosphaera apis), the bacterium Paenibacillus larvae, and several viruses. Data
on environmental factors, beekeeping management practice, and pesticides were
also collected. All data were statistically analyzed in respect to the
overwintering mortality of the colonies. We can demonstrate for several factors
that they are significantly related to the observed winter losses of the
monitored honey bee colonies: (i) high varroa infestation level, (ii) infection
with deformed wing virus (DWV) and acute bee paralysis virus (ABPV) in autumn,
(iii) queen age, and (iv) weakness of the colonies in autumn. No effects could
be observed for Nosema spec. or pesticides. The implications of these findings
will be discussed.'

4.  Belgium

Another professional study looking at all possible factors affecting colony survival.  There was a comprehensive assessment of the colonies under study for all possible pests and pathogens and also a long list of pesticides investigated, including miticides.  The presentation is in French but clear enough for those with some knowledge of the language:

http://www.fsagx.ac.be/zg/Sujets_d_actualite/Abeilles/Rapport%20final%2014%20d%C3%A9cembre%202006.pdf

The work was thorough and although only 16 apiaries were involved there was detailed analysis of many factors including the foraging landscape around each apiary and the imidacloprid exposure via treated maize fields.  The conclusions were clear: Varroa was the main problem with a secondary contribution from AFB.  Associations with levels of pesticide exposure were not found. At the end they mention work published in 6 other European countries in 2005 and 2006.  All implicated pathogens, primarily Varroa but also Nosema in Spain.

5.  France

In France there is a maelstrom of suspicion of pesticides and clearly the issue has become hugely political.  The beekeeping community largely believed that pesticides were behind their problems.  However the evidence emerging from the research there that was funded to take a broad view of possible causes of bee losses, like other European studies, points towards Varroa and other pathogens and not pesticides.  Again there has been comprehensive testing for pesticide residues (including miticides) in colonies under study and again the losses are not associated with their levels.  This report is large and thorough but, for once, is bilingual and well worth a read.

http://www.afssa.fr/Documents/SANT-Ra-MortaliteAbeilles.pdf

There are French beekeepers and observers bemoaning the fact that much of the funding in France was directed to areas insisted upon by the French beekeepers. Their suspicion of pesticides means that only a little of the funds went to look at the broader picture and some areas of research, including on viruses, were neglected while a largely barren major effort was directed at pesticides.

6.  Back to the USA.

Professor May Berenbaum of Illinois was interviewed in an internet radio broadcast recently.  Her research was on the responses of bees at the level of expression of genes.  This is a powerful way to determine what organisms are doing in reponse to challenges, and her results showed that CCD colonies were not switching on genes to respond to a threat from pesticides but instead were showing the effects of infection with some RNA viruses and her conclusion was that viral epidemics were the main cause of CCD.  This was published in PNAS, one of the best journals:

http://www.pnas.org/content/106/35/14790.short

7.  The UK

Giles Budge and colleagues at the NBU have investigated the causes of colony losses in England and Wales.  Again, in line with other work in Europe, Varroa, Nosema and viruses were implicated and pesticides not.  Some of the early results are presented here:

https://secure.fera.defra.gov.uk/beebase/downloadNews.cfm?id=28

What does all this add up to?  Several research projects with professional bee researchers involved in investigating many factors affecting real beekeepers’ real colonies, and study after study is reporting no apparent effect of pesticides. This is very far from the impression gained from reading some of the bee literature and certainly from reading some newspapers.

Does all this mean that pesticides are off the hook?  No, not completely. No-one should discount that they might have an effect along with all the other things that affect bees such as a lack of forage, unsuitable weather, problems of nutrition, pests and diseases, inappropriate bee genetics and problems of management. But given the findings of impartial, experienced bee researchers then anyone trying to pin the blame for colony ill-health and colony losses largely on pesticides (or miticides) is doing beekeeping a disservice. It is especially worrying that attention is now moving to combinations of effects (farm pesticides and miticides) when again there is absolutely no indication that bees suffer losses of individuals or odd behaviour when exposed to maximum levels of pesticides (when working farm crops such as oilseed rape) or exposed to maximum levels of miticides (when being treated). This just fuels – for no good reason – the idea that Varroa control should switch to methods such as powdered sugar which are too inefficient for routine use.

Gavin Ramsay

2 May 2011

PS These are personal interpretations of the scientific literature. I do not speak for the SBA any longer and especially not on the issue of the science of pesticide concerns.