New publication and website show worldwide distribution of honey bee pests and pathogens

Western honey bees Apis mellifera L. have an important role as pollinators of agricultural crops, honey producers, and producers of hive-related commodities such as beeswax, propolis, and royal jelly. Knowing the global distribution of honey bee pests and pathogens is key to developing strategies for their control and limiting their further spread.

A review of honey bee pest and pathogen distribution was conducted by scientists at The University of Florida, Plant & Food Research and Bayer CropScience to update the work of Ellis & Munn (2005), with a special emphasis on new and emerging pests/pathogens and noting the spread of those pest/pathogens discussed in earlier reviews.

The updated review was also motivated by increased interest in loss rates of managed honey bee colonies, which has resulted in more publications on honey bee pests and pathogens.

An interactive system was adopted where the maps and tables provided at can be updated as needed by the author team. Members of the team will update the maps and tables early every year to reflect new information reported for any pest/pathogen the previous year. Additionally, maps will be updated if new (validated) findings are brought to their attention by readers/ users (details available on the website).

All tables and maps are free to download and use with appropriate citation (maps are open source). High resolution images were used to generate each map. You can see country status by zooming into the region or country of interest if the land area is too small to see at the whole-map level.

The following geographical considerations were noted by the scientists:

  • Even if a small area of the country is affected by the pest or pathogen, the whole country will still be marked as the pathogen being present.
  • Territories or states in the same country but separated by landmasses or bodies of water were not considered the same country, and treated separately.
  • Any now-defunct political entities were reported from the new geopolitical entities where possible. When not possible, all new entities that incorporated part(s) of the old entities were highlighted. This is intended to be fixed in the future by incorporating GPS coordinates for the locations where the various pathogens/pests were found.
  • Not all countries have robust beekeeping and/or scientific communications. Therefore if a pest/pathogen is not marked as ‘present’ in a country, it does not necessarily mean that it is not present.

Journal references

Boncristiani H, Ellis JD, Bustamante T, Graham J, Jack C, Kimmel CB, Mortensen A, Schmehl DR 2020. World Honey Bee Health: The global distribution of western honey bee (Apis mellifera L.) pests and pathogens. Bee World, DOI: 10.1080/0005772X.2020.1800330

Ellis JD, Munn PA 2005. The worldwide health status of honey bees. Bee World, 86:4, 88-101, DOI: 10.1080/0005772X.2005.11417323

Source:  Plant & Food Research

Glyphosate and the decline of honey bees – expert reaction to new research

New research from the US has found the active ingredient in the weed killer Roundup could be contributing to the decline of honey bees.

Published in PNAS, the research, titled ‘Glyphosate perturbs the gut microbiota of honey bees’, found glyphosate altered the gut bacteria in bees – making them more susceptible to harmful bacteria and infections and hindering their ability to pollinate.

Better guidelines for glyphosate use are needed especially surrounding bee exposure, according to the researchers, because current guidelines assume bees are not harmed by the herbicide.

The herbicide glyphosate is expected to be innocuous to animals, including bees, because it targets an enzyme only found in plants and microorganisms, the paper says. However, bees rely on a specialized gut microbiota that benefits growth and provides defense against pathogens.

Most bee gut bacteria contain the enzyme targeted by glyphosate, but vary in whether they possess susceptible versions and, correspondingly, in tolerance to glyphosate.

Exposing bees to glyphosate alters the bee gut community and increases susceptibility to infection by opportunistic pathogens.

Understanding how glyphosate impacts bee gut symbionts and bee health will help elucidate a possible role of this chemical in colony decline.

Better guidelines for glyphosate use are needed especially surrounding bee exposure, according to the researchers, because current guidelines assume bees are not harmed by the herbicide.

The Science Media Centre has published expert comment collected by the UK and Australian Science Media Centres

Dr Andres Arce, evolutionary ecologist at Imperial College London:

“Motta et al investigated whether dietary exposure to glyphosate, a commonly used herbicide thought to have a low toxicity in animals, could alter the bacterial gut microbiome of honeybees. The bacterial microbiome plays a number of roles in keeping bees healthy, such as by helping them resist disease and process nutrients, so any pesticide induced alterations to the microbiome could indirectly affect bee health.

“The study demonstrates that the bacterial microbiota in honeybees can be altered by exposure to glyphosate. Crucially, Motta et al also demonstrate that pesticide exposure also appears to affect bee health by increasing susceptibility to a common insect pathogen. Interestingly, bees that were not exposed to the pathogen showed comparable survival to bees that were never given glyphosate.

“This study highlights how commonly used pesticides, even those marketed as being targeted at specific plants or animals, can unintentionally affect non-target organisms. It also highlights the importance of considering exposure over an extended period of time (>1 day) and the importance of multiple stressors, such as the effect of pesticide and disease. Both are typically overlooked when assessing pesticide safety and both are likely to be important in the wild.

“This study is part of a growing trend towards looking at more complex interactions between animals, their microbiome, and interacting stressors. Understanding these interactions is essential to quantify the hazards associated with pesticide use and is essential if we are to develop strategies that allow us to continue using pesticides, which are vital to modern agriculture, whilst minimising their effects on the natural world.”

Prof Dave Goulson, Professor of Biology at the University of Sussex:  

“This is a well conducted study which finds that ingestion of low concentrations of glyphosate alters the natural bacterial gut community of honeybees and makes them more susceptible to harmful pathogens. In recent years it has become increasingly apparent that gut bacteria play a vital role in maintaining good health, in organisms as diverse as bees and humans. The finding that these bacteria are sensitive to the most widely used pesticide in the world is thus concerning.

“One might wonder how bees could ever become exposed to a herbicide in the real world. Glyphosate kills plants, so contaminated flowers will soon be dead and of no interest to bees. Nonetheless, glyphosate IS sometimes found in bee food stores, at concentrations similar to those used in this study.

“Those of us that study bees have long ago come to the conclusion that colony health is adversely affected by a number if interacting stressors, including exposure to cocktails of insecticides and fungicides, impacts of pathogens, and effects of poor nutrition. It now seems that we have to add glyphosate to the list of problems that they face. This study is also further evidence that the landscape-scale application of large quantities of pesticides has negative consequences that are often hard to predict.

“It is worth noting that, although this study was of bees, these findings are highly relevant to other beneficial organisms for almost all animals harbour beneficial gut microbes.”

Dr Oliver Jones, Associate Professor of Chemistry at RMIT University in Melbourne, Australia:

“This is quite a complex piece of work which investigates the effect of the pesticide Glyphosate on some of the bacteria that live in the guts of bees (the bee microbiome), rather than its effects on the bees themselves. The authors state that Glyphosate exposure can change the type of bacteria in the bee’s gut and this change may have negative effects on the bees’ overall health by, potentially, making them more susceptible to pathogens.

“The work is an interesting and novel approach. However, to my mind the doses of glyphosate used were rather high. The exposures were also relatively short so it is not known if any of the changes that were seen were short or long term. In addition, only 20% of the adult bees that were exposed to the pesticide were recovered and tested further so we don’t know what the effects on the other 80% were.

“A confusing result is that the bees exposed to the highest dose of Glyphosate seems to show far fewer effects than those exposed to a lower dose after three days. This effect was shown to be reproducible, but was not explained.

“It should perhaps be kept in mind that the paper shows only that Glyphosate can potentially interfere with the bacteria in the bee gut, not that it actually does so in the environment. There are also countries, such as Australia, where Glyphosate is used but where bees are generally doing well.

“So in short, I think the work is a potentially interesting piece of the overall puzzle of bee health, but not the whole picture.”

Dr Jones had no conflict of interest to declare.

No others were received.

Source:  Science Media Centre

Understanding non-lethal effects of pesticides on honey bees

Scientists are developing a new way of studying bees in the laboratory to determine whether pesticides are having a negative effect on their health and behaviour.

Understanding the effects of pesticides on honey bee health is imperative in making informed choices about the risks associated with use of pesticides in crop production. Previously, tests have focused on whether the pesticide kills developing bees, but scientists are developing new lab-based methods for understanding the non-lethal effects of pesticides on bees.

Dr Ashley Mortensen, who recently joined Plant & Food Research’s Pollination & Apiculture Team, has been studying bee behaviour as part of her PhD studies at the University of Florida. Tests for pesticide responses involve rearing honey bees in a lab environment prior to exposure to the pesticide. Dr Mortensen’s research analysed changes in behaviour that occur as a result of rearing bees in an artificial environment so that these can be factored into standardised tests and not confused with other changes that may occur as a response to pesticide exposure.

Her research has been published in the journal Behavioural Ecology and Sociobiology.

“One obvious way that stressors, such as pesticides, pests or disease, prevent bees from pollinating plants is by killing the bees either during immature development or by reducing the lifespan of the adults,” says Dr Mortensen.

“However, even if the bees don’t die, changes in their behaviour after exposure to one or more stressor during development could reduce bees’ efficiency at hive tasks such as rearing brood, tending to the queen, or foraging for nectar or pollen.

“This work is expected to further our understanding of how pesticides or other developmental stressors, like pathogens, temperature change and more, could alter the behaviour of adult bees.”

Dr Mortensen’s research will inform the development of new standardised tests for use by regulatory agencies around the world to determine what pesticides are safe for use in the environment and how or when they can be used in crop production.

New Zealand has more than 7,800 registered beekeepers with close to 800,000 hives producing nearly 15,000 tonnes of honey each year (Fresh Facts 2017). Commercial hives are used in the pollination of many of New Zealand’s high value fruit crops, including kiwifruit, apples and berryfruit.

NZ experts react to results of field tests on insecticide impact on bees

The Science Media Centre has posted comments (HERE) from New Zealand scientists on two large-scale field experiments on the effects of certain insecticides on honey bees and wild bees.

Neonicotinoids, insecticides that have been broadly applied to many major crops, have been implicated in the decline of bees globally.

Two studies, published this week in Science, found mixed results.

* Insecticide residue in bees nests was associated with lower reproductive success in Germany, Hungary and the UK, but survival over winter was unaffected in Germany.

* The second study, in Canada, found that worker bees exposed to neonicotinoids had lower life expectancies and their colonies were more likely to lose queens.

More information about the studies is available HERE.  

Dr David Pattemore, pollination & apiculture team leader, Plant & Food Research, comments:

“Two new studies published this week claim to show negative effects of neonicotinoids on honey bee colonies in real-world scenarios. One study does not really present clear evidence to support this conclusion, but the second does link neonicotinoid exposure to key longevity, hygiene and reproductive traits of honey bee colonies.

“One of the studies demonstrates synergistic effects between fungicides and neonicotinoids, which increase the mortality of bees exposed to the pesticides. One of the studies shows evidence of negative neonicotinoid effects on bumblebee and solitary bee reproductive output.

“Overall these provide  little more evidence about the effects of neonicotinoids, but there is still no scientific consensus emerging about the effect of neonicotinoids on honey bee health in realistic field situations.

“These two studies are unlikely to have implications for New Zealand in terms of regulations for the use of neonicotinoid pesticides. After reading these papers, my view is that we need to consider the synergistic effects of multiple agrochemicals on bee health and that it is timely to consider establishing long-term monitoring programmes for wild pollinator populations, including native and introduced bees, in New Zealand.”

Note: Dr Pattemore has also written a blog in response to the studies. Plant & Food Research occasionally has contracts to evaluate the efficacy or toxicity of pesticides, but Dr Pattemore hasn’t been personally involved in these trials to date.

Dr Jacqueline Rowarth, chief scientist, Environmental Protection Authority, comments:

“Research published this week indicates that prolonged exposure to neonicotinoid insecticides can negatively affect bees. The researchers also concluded that local environment and species influence impact of the chemicals. The research was done in the northern hemisphere near oilseed rape crops in Germany, Hungary and the UK, and in the commercial corn (maize)-growing area of Canada.

“For New Zealand, and the Environmental Protection Authority (EPA) which regulates the use of chemicals, focus on new research results includes applicability. Experts scan for new research constantly, and consider the results in the New Zealand context.

“New Zealand does not have the large tracts of land under cropping that are common in the northern hemisphere, and does have very strict regulations around timing of chemical application (e.g., not when the target for protection is flowering), delivery method, and seed treatment dust reduction. The northern hemisphere research comments on neonicotinoid dust being found in the pollen of flowering species surrounding crops ‘despite the use of dust-reducing lubricants’.

“In New Zealand the use of neonicotinoids in seed treatment has enabled very low rates of active ingredient, thereby reducing the number of insecticide treatments required to protect the crop. Residues of neonicotinoids have not been found in pollen or nectar of when the insecticide has been applied at label rates.

“The chemical of particular concern in the new research, clothianidin, is a seed treatment approved for cereals, maize/sweetcorn, grasses and forage brassicas. Only the brassica is a flowering crop, and it is eaten before it reaches maturity. The crops are not considered to be attractive to bees, unlike oilseed rape.

“The northern hemisphere researchers also comment on the increase in negative effects in bees when fungicides were used as well as the neonicotinoids and the confounding factor of climate change. This points to the complexity of identifying the problems with chemical exposure. Cold damp winters affect bee survival and there is an interaction with pests as well as food supplies (quantity and quality). These factors are difficult to disentangle. In New Zealand, feral bee numbers have been decimated by varroa mite, but managed bee hive numbers have increased. In Australia, which is varroa-free, no problems with bee survival have been reported. Neonicotinoids have been used for two decades.

‘Recognising on-going public concerns, the EPA is developing a pollinator strategy, working with the chemical industry and the apiculturalists, to ensure that decisions about chemical use are made on the basis of robust and appropriate research, whilst supporting pollinators and pollination.”

The EPA sets the rules for use of hazardous substances under the Hazardous Substances and New Organisms Act 1996 by assessing the environmental and economic risks and benefits to New Zealanders and the environment.

Associate Professor Peter Dearden, director, Genetics Otago, University of Otago, comments:

“The two Science papers (Tsvetkov et al and Woodcock et al) attempt to test the effect of common pesticides on bee colonies in situations that are as close to reality (in terms of exposure) as possible. This is a tricky thing to do, and something that has been criticised in previous studies of neonicotinoid exposure in the past. These papers do this well, and show that the effects of neonicotinoids are complex, but detrimental to bees.

“In Canada, Tsvetkov et al show clearly that neonicotinoid seed coatings have detrimental effects on bees, and that these effects are exacerbated by other agricultural chemicals. Woodcock et al show similar things in Europe, but add that the different cocktails of agricultural chemicals used in different countries have different effects, causing variation in the impact on bees in each location.

“This complexity of response to insecticides is not surprising, but these results clearly show that in general neonicotinoid exposure, even in sublethal doses, in field realistic tests, is detrimental to bees. This is a problem, but so is growing crops without pesticides.

“There is a balance to be had here if we are to produce food in large enough quantities to feed a burgeoning human population, without devastation of managed, and wild, pollinators. The hope of these papers is the variability seen in European countries, and the synergistic effects with other agri-chemicals seen in Canada. This suggests that we may be able to identify ways of using these chemicals, or combinations of these chemicals, to be less damaging to bees, and wild insects.

“The key message is, however, that in field realistic conditions, neonicotinoid seed treatments are bad for pollinators. Limiting their use in New Zealand, as well as researching how to develop pollinator friendly insecticides, or using insecticides in a less damaging way, is critical. The European studies show that agricultural practice varies the impact on bees. We need this research to be done in New Zealand to see how our practice is affecting our bees.”

Note: Dr Dearden has a Ministry of Business, Innovation and Enterprise grant to develop bee-friendly insecticides.

Professor Phil Lester, insect ecologist, Victoria University of Wellington, comments:

“Neonicotinoids are some of the most widely used pesticides in the world. They were developed in the hope that their use would be less harmful to non-target organisms, because by only coating crop seeds in this pesticide prior to planting the need for spraying entire environments can be reduced. Neonicotinoids are then expressed throughout the mature plant and affect only those organisms eating the plant. The issue is that neonicotinoids are expressed in the pollen and nectar too, which beneficial organisms like bees collect and eat.

“The European Union imposed a temporary moratorium on the use of the three key neonicotinoids in 2013 because of their potential to harm honey bees. In contrast, the government of New Zealand has joined with Australia in not imposing a ban or moratorium on the use of these chemicals. I think our governments have made exactly the right decision at this time.

“The work published by Tsvetkov and colleagues in Science today that indicates ‘Chronic exposure to neonicotinoids reduces honey-bee health near corn crops’. This study agrees with a large amount of previous work. If honey bees are exposed to and feed on high amounts of neonicotinoids the outcome is simply bad. Workers and queens will die. For those experiencing a sub-lethal dose, their foraging becomes less efficient. They undertake reduced hygienic behaviour in the hive and their immune system seems to be impaired. And their tolerance of other stressors bees experience in bee environments, in this case a fungicide, is reduced.

“The Tsvetkov study in cornfields of Canada clearly shows that field-realistic exposure to neonicotinoids can substantially reduce honey bee health.

“The second paper in Science today is from work within three different countries and examines three different bees. It also attempted to use field-realistic exposure to neonicotinoids. Populations of honey bees, bumble bees and a solitary bee were followed in the United Kingdom, Hungary and Germany.

“The team of authors led by Woodcock examined two neonicotinoid pesticides. They found a fascinatingly mixed bag of results. Both neonicotinoids resulted in significantly reduced numbers of honey bee eggs being produced in Hungary. But exposure to both pesticides in Germany resulted in significantly more eggs being produced. Neonicotinoids also seemed to result in higher numbers of workers surviving winter in Germany. In Hungary, fewer workers survived winter after exposure to one pesticide, but not the other chemical. Similarly, in the United Kingdom, there were negative and some positive effects of exposure to the different neonicotinoids.

“A take-home message the Woodcock publication is that the use different neonicotinoids can have different effects and these effects can be very country specific. After reading these results, if I was a grower in Germany I would be starting to question the European Union’s temporary moratorium.

“These studies highlight that for countries like New Zealand to effectively manage the use of neonicotinoid pesticides, we need data. We need to know what the effects of neonicotinoids are in our specific country and in the way we specifically use them. And we also need to know what the effects would be if we took them away. I’ve read reports that growers in the UK have had to now revert to broad spectrum pesticides that are considered worse for the environment and mean they cannot grow certain crops.

“In 2013, the Australian government undertook a review of “Neonicotinoids and the Health of Honey Bees in Australia”. They concluded that “the introduction of the neonicotinoids has led to an overall reduction in the risks to the agricultural environment from the application of insecticides”. They don’t currently think there is the scientific evidence to show that neonicotinoids are of widespread harm to bees in Australia. In fact, they stated that “The introduction of the neonicotinoid insecticides has brought a number of benefits, including that they are considerably less toxic to humans (and other mammals) than the organophosphorus and carbamate insecticides they have significantly replaced.

“Honey bees in New Zealand have a plethora of known and scientifically demonstrated threats. Our honey bees have invasive, blood sucking mites. They have the Deformed wing virus which has been described as a key contributor to colony collapse around the globe. Our bees have bacterial pathogens like American Foulbrood that result in beekeepers burning their bees and hives. Fungal diseases are widespread. We also have management issues with the higher-than-ever numbers of managed hives, which are often managed poorly and over-stocked. These are real and known issues occurring for our honey bees now.

“I hope that the New Zealand government acts on studies like those from the Woodcock and Tsvetkov teams.

“But I’d personally be disappointed if that action was anything other than evidence- and science-based. Let’s gather the data. Then make the decision. It might be that like results from the Tsvetkov study, we find neonicotinoids are bad for our bees. Or we might be a Germany and find that they have few or even positive effects.”

Note: Professor Lester’s comments also appeared on The Conversation.

Otago researchers find bees “dumb down” after ingesting tiny doses of pesticide

Honey bees’ learning and memory capacity is reduced by the ingestion of very small doses of the pesticide chlorpyrifos, potentially threatening the bees’ survival, new University of Otago research suggests.

Researchers from the Departments of Zoology and Chemistry collected bees from 51 hives across 17 locations in Otago and measured their chlorpyrifos levels. They detected low levels of pesticide in bees at three of the 17 sites and in six of the 51 hives they examined.

Detecting chlorpyrifos was not a surprise. In 2013, Associate Professor Kim Hageman and her team from Otago’s Department of Chemistry showed that chlorpyrifos was detectable in air, water, and plant samples even in non-sprayed areas of the country, because this pesticide has a high ability to volatilise and travel great distances.

In the laboratory they then fed other bees with similar amounts of the pesticide, which is used around the world to protect food crops against insects and mites, and put them through learning performance tests.

Study lead author Dr Elodie Urlacher says they found chlorpyrifos-fed bees had worse odour-learning abilities and also recalled odours more poorly later, even though the dose they ingested is considered to be “safe”.

“For example, the dosed bees were less likely to respond specifically to an odour that was previously rewarded. As honeybees rely on such memory mechanisms to target flowers, chlorpyrifos exposure may be stunting their effectiveness as nectar foragers and pollinators,” Dr Urlacher says.

The study identified the threshold dose for sub-lethal effects of chlorpyrifos on odour-learning and recall as 50 picograms of chlorpyrifos ingested per bee, she says.

“This amount is thousands of times lower than the lethal dose of pure chlorpyrifos, which is around 100 billionths of a gram. Also, it is in the low range of the levels we measured in bees in the field.”

The current study is the first to establish the threshold at which a pesticide has an effect on memory specificity in bees while also measuring doses in bee populations in the field, she says.

“Our findings raise some challenging questions about regulating this pesticide’s use. It’s now clear that it is not just the lethal effects on bees that need to be taken into account, but also the serious sub-lethal ones at minute doses,” Dr Urlacher says.

The research, which appears in the Journal of Chemical Ecology, was supported by the Marsden Fund of New Zealand.

Publication details:

Measurements of Chlorpyrifos Levels in Forager Bees and Comparison with Levels that Disrupt Honey Bee Odor-Mediated Learning under Laboratory Conditions

Elodie Urlacher, Coline Monchanin, Coraline Rivière, Freddie-Jeanne Richard, Christie Lombardi, Sue Michelsen-Heath, Kimberly J. Hageman, Alison R. Mercer

DOI: 10.1007/s10886-016-0672-4

Study by US govt agencies says a mix of factors is wiping out honeybee colonies

A comprehensive federal government study published in the US says the devastation of American honeybee colonies is the result of a complex stew of factors, including pesticides, parasites, poor nutrition and a lack of genetic diversity.

The report has been published in the same week as European officials took steps toward banning a class of pesticides known as neonicotinoids, derived from nicotine, that they consider a critical factor in the mass deaths of bees there.

Agcarm, the New Zealand organisation which represents manufacturers and distributors of crop protection and animal health products, challenged the evidence in support of the European Union curbs.

Officials in the United States Department of Agriculture, the Environmental Protection Agency and others involved in the bee study agreed there was not enough evidence to support a ban on one group of pesticides, and that the costs of such action might exceed the benefits.

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