Honey bees experience multiple health stressors out-in-the-field

It's not a single pesticide or virus stressing honey bees, and affecting their health, but exposure to a complex web of multiple interacting stressors encountered while at work pollinating crops, found new research out of York University.

Scientists have been unable to explain increasing colony mortality, even after decades of research examining the role of specific pesticides, parasitic mites, viruses or genetics. This led the research team to wonder if previous studies were missing something by focussing on one stressor at a time.

"Our study is the first to apply systems level or network analyses to honey bee stressors at a massive scale. I think this represents a paradigm shift in the field because we have been so focussed on finding the one big thing, the smoking gun," says corresponding author of the new paper York Faculty of Science Professor Amro Zayed, York Research Chair in Genomics. "But we are finding that bees are exposed to a very complicated network of stressors that change quickly over time and space. It's a level of complexity that we haven't thought about before. To me, that's the big surprise of this study."

The paper, Honey bee stressor networks are complex and dependent on crop and region, published today in Current Biology, takes a much broader look at the interplay of stressors and their effects. The study team also included researchers from the University of British Columbia, Agriculture and Agri-Food Canada, the University of Victoria, the University of Lethbridge, the University of Manitoba, l'Université Laval, the University of Guelph, and the Ontario Beekeepers' Association.

Not all stressors are the same, however. Some stressors are more influential than others -- what researchers call the social media influencers of the bee world -- having an outsized impact on the architecture of a highly complex network and their co-stressors. They also found that most of these influencer stressors are viruses and pesticides that regularly show up in combination with specific other stressors, compounding the negative effects through their interactions.

"Understanding which stressors co-occur and are likely to interact is profoundly important to unravelling how they are impacting the health and mortality of honey bee colonies," says lead author, York Postdoctoral Fellow Sarah French of the Faculty of Science.

"There have been a lot of studies about major pesticides, but in this research, we also saw a lot of minor pesticides that we don't usually think about or study. We also found a lot of viruses that beekeepers don't typically test for or manage. Seeing the influencer stressors interact with all these other stressors, whether it be mites, other pesticides or viruses, was not only interesting, but surprising."

French says the way influencer stressors co-occur with other stressors is similar to the way humans experience co-morbidities, such as when someone is diagnosed with heart disease. They are more likely to also have diabetes or high blood pressure or both, and each one impacts the other. "That's similar to the way we examine bee colonies. We look at everything that's going on in the colony and then compare or amalgamate all the colonies together to look at the broader patterns of what is happening and how everything is related. Two or multiple stressors can really synergize off each other leading to a much greater effect on bee health."

From Québec to British Columbia, honey bee colonies were given the job of pollinating some of Canada's most valuable crops -- apples, canola oil and seed, highbush and lowbush blueberry, soybean, cranberry and corn. The study covered multiple time scales, providing numerous snapshots, rather than the usual single snapshot in time. The research team found that honey bees were exposed to an average of 23 stressors at once that combined to create 307 interactions.

Honey bees are a billion dollar industry. In 2021, honey bees contributed some $7 billion in economic value by pollinating orchards, vegetables, berries and oil seeds like canola, and produced 75 to 90 million pounds of honey. Figuring which stressors would provide the most benefit if managed would go a long way toward developing the right tools to tackle them, something beekeepers are often lacking.

The research is part of the BEECSI: 'OMIC tools for assessing bee health project funded to the tune of $10 million by Genome Canada in 2018 to use genomic tools to develop a new health assessment and diagnosis platform powered by stressor-specific markers.

More research is needed to unravel how the stressors are interacting and impacting honey bee mortality and colony health going forward, says French. "It's really teasing apart which of these compounds might have that relationship and how can we build off this to study those specific relationships."

It can't come soon enough, honey bees are currently facing poor health, colony loss, parasites, pathogens and heightened stressors worldwide. Some beekeepers in this country and the United States face a loss over winter of up to 60 per cent of their colonies.

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Scientists engineer plant microbiome to protect crops against disease

Breakthrough could dramatically cut the use of pesticides and unlock other opportunities to bolster plant health

Scientists have engineered the microbiome of plants for the first time, boosting the prevalence of 'good' bacteria that protect the plant from disease.

The findings published in Nature Communications by researchers from the University of Southampton, China and Austria, could substantially reduce the need for environmentally destructive pesticides.

There is growing public awareness about the significance of our microbiome -- the myriad of microorganisms that live in and around our bodies, most notably in our guts.

Our gut microbiomes influence our metabolism, our likelihood of getting ill, our immune system, and even our mood.

Plants too host a huge variety of bacteria, fungi, viruses, and other microorganisms that live in their roots, stems, and leaves.

For the past decade, scientists have been intensively researching plant microbiomes to understand how they affect a plant's health and its vulnerability to disease.

"For the first time, we've been able to change the makeup of a plant's microbiome in a targeted way, boosting the numbers of beneficial bacteria that can protect the plant from other, harmful bacteria," says Dr Tomislav Cernava, co-author of the paper and Associate Professor in Plant-Microbe Interactions at the University of Southampton.

"This breakthrough could reduce reliance on pesticides, which are harmful to the environment. We've achieved this in rice crops, but the framework we've created could be applied to other plants and unlock other opportunities to improve their microbiome. For example, microbes that increase nutrient provision to crops could reduce the need for synthetic fertilisers."

The international research team discovered that one specific gene found in the lignin biosynthesis cluster of the rice plant is involved in shaping its microbiome.

Lignin is a complex polymer found in the cell walls of plants -- the biomass of some plant species consists of more than 30 per cent lignin.

First, the researchers observed that when this gene was deactivated, there was a decrease in the population of certain beneficial bacteria, confirming its importance in the makeup of the microbiome community.

The researchers then did the opposite, over-expressing the gene so it produced more of one specific type of metabolite -- a small molecule produced by the host plant during its metabolic processes.

This increased the proportion of beneficial bacteria in the plant microbiome.

When these engineered plants were exposed to Xanthomonas oryzae -- a pathogen that causes bacterial blight in rice crops, they were substantially more resistant to it than wild-type rice.

Bacterial blight is common in Asia and can lead to substantial loss of rice yields.

It's usually controlled by deploying polluting pesticides, so producing a crop with a protective microbiome could help bolster food security and help the environment.

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Honey bee colony loss in the U.S. linked to mites, extreme weather, pesticides

About one-third of the food eaten by Americans comes from crops pollinated by honey bees, yet the insect is dying off at alarming rates. In one year alone, between April of 2019 and April of 2020, one study reported a 43% colony loss in honey bees across the United States.

A new study led by Penn State researchers provides preliminary insight on the potential effects of several variables, including some linked to climate change, on honey bees. Their findings show that honey bee colony loss in the U.S. over the last five years is primarily related to the presence of parasitic mites, extreme weather events, nearby pesticides, as well as challenges with overwintering, according to a new study led by Penn State researchers. The study took advantage of novel statistical methods and is the first to concurrently consider a variety of potential honey bee stressors at a national scale. The study, published online in the journal Scientific Reports, suggests several areas of concern to prioritize in beekeeping practices.

"Honey bees are vital pollinators for more than 100 species of crops in the United States, and the widespread loss of honey bee colonies is increasingly concerning," said Luca Insolia, first author of the study, a visiting graduate student in the Department of Statistics at Penn State at the time of the research, and currently a postdoctoral researcher at the University of Geneva in Switzerland. "Some previous studies have explored several potential stressors related to colony loss in a detailed way but are limited to narrow, regional areas. The one study that we know of at the national level in the United States explored only a single potential stressor. For this study, we integrated many large datasets at different spatial and temporal resolutions and used new, sophisticated statistical methods to assess several potential stressors associated with colony collapse across the U.S."

The research team, composed of statisticians, geographers, and entomologists, gathered publicly available data about honey bee colonies, land use, weather, and other potential stressors from the years 2015 to 2021. Because these data came from a variety of sources, they varied in resolution over both space and time. The weather data, for example, contained daily data points for areas only few square miles in size, but data on honey bee colonies was at the state level for a several-month period.

"In order to analyze the data all together, we had to come up with a technique to match the resolution of the various data sources," said Martina Calovi, corresponding author of the study, a postdoctoral researcher in the Department of Ecosystem Science and Management at Penn State at the time of the research, and currently an associate professor of geography at the Norwegian University of Science and Technology. "We could have just taken an average of all the weather measurements we had within a state, but that boils all the information we have into one number and loses a lot of information, especially about any extreme values. In addition to averaging weather data, we used an 'upscaling' technique to summarize the data in several different ways, which allowed us to retain more information, including about the frequency of extreme temperature and precipitation events."

The researchers used the resulting integrated resolution-matched dataset -- which they have made available for use by other researchers -- alongside sophisticated statistical modeling techniques that they developed to assess the large number of potential stressors at the same time.

The research team found that several stressors impacted honey bee colony loss at the national level, including the presence of nearby pesticides, frequent extreme weather events, and weather instability. Colony loss was also related to the presence of parasitic mites, Varroa destructor, which reproduce in honey bee colonies, weaken the bees, and potentially expose them to viruses. The researchers also found that losses typically occurred between January and March, likely related to challenges with overwintering, but that some states do not follow this pattern.

"Our results largely reinforce what regional studies have observed and confirm that regional patterns around these stressors are actually more widespread," said Insolia, a beekeeper himself. "These results also inform actions that beekeepers could take to help circumvent these stressors and protect their colonies, including treatments for the Varroa mite‚ especially in areas of weather instability. Beekeepers could also consider strategies to move their colonies to areas with high food availability or away from nearby pesticides or to provide supplementary food during certain seasons or months with frequent extreme weather events."

The researchers note that having data about beekeeping practices and colony loss at a finer resolution would allow validation of their results and a more nuanced look at honey bee stressors.

"It would be incredibly beneficial to explore beekeeping practices at a finer scale than the state level," said Calovi. "In many cases, beekeeping associations and other organizations collect this data, but it is not made available to researchers. We hope our study will help motivate more detailed data collection as well as efforts to share that data -- including from smaller organizations such as regional beekeeper associations."

The research team also found a strong relationship between colony loss and a broad category of beekeeping practices noted on a USDA survey as "other," which contained everything from hives being destroyed to food scarcity to queen failure. They noted that collecting this data in more detail and breaking up this catch-all type variable would improve their ability to connect particular stressors to colony collapse.

"A changing climate and high-profile extreme weather events like Hurricane Ian -- which threatened about 15% of the nation's bees that were in its path as well as their food sources -- are important reminders that we urgently need to better understand the stressors that are driving honey bee colony collapse and to develop strategies to mitigate them," said Francesca Chiaromonte, professor of statistics and the holder of the Lloyd and Dorothy Foehr Huck Chair in Statistics for the Life Sciences at Penn State and a senior member of the research team. "Our results highlight the role of parasitic mites, pesticide exposure, extreme weather events, and overwintering in bee colony collapse. We hope that they will help inform improved beekeeping practices and direct future data collection efforts that allow us to understand the problem at finer and finer resolutions."

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Common pesticide may contribute to global obesity crisis

A commonly-used pesticide could be partially responsible for the global obesity epidemic, says a study led by McMaster University scientists.

Researchers discovered that chlorpyrifos, which is banned for use on foods in Canada but widely sprayed on fruits and vegetables in many other parts of the world, slows down the burning of calories in the brown adipose tissue of mice. Reducing this burning of calories, a process known as diet-induced thermogenesis, causes the body to store these extra calories, promoting obesity.

Scientists made the discovery after studying 34 commonly used pesticides and herbicides in brown fat cells and testing the effects of chlorpyrifos in mice fed high calorie diets. Their findings were published in Nature Communications and could have important implications for public health.

"Brown fat is the metabolic furnace in our body, burning calories, unlike normal fat that is used to store them. This generates heat and prevents calories from being deposited on our bodies as normal white fat. We know brown fat is activated during cold and when we eat," said senior author Gregory Steinberg, professor of medicine and co-director of the Centre for Metabolism, Obesity, and Diabetes Research at McMaster.

"Lifestyle changes around diet and exercise rarely lead to sustained weight loss. We think part of the problem may be this intrinsic dialling back of the metabolic furnace by chlorpyrifos."

Steinberg said chlorpyrifos would only need to inhibit energy use in brown fat by 40 calories every day to trigger obesity in adults, which would translate to an extra five lbs of weight gain per year.

He said that while several environmental toxins including chlorpyrifos have been linked to rising obesity rates in both humans and animals, most of these studies have attributed weight gain to increases in food intake and not the burning of calories.

While the use of chlorpyrifos on foods is banned in Canada, imported produce may still be treated with it.

"Although the findings have yet to be confirmed in humans, an important consideration, is that whenever possible consume fruits and vegetables from local Canadian sources and if consuming imported produce, make sure it is thoroughly washed," said Steinberg.

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