‘Murder hornets’: race to protect North America’s honeybees from giant invader

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Amateur beekeepers and scientists do ‘the whole CSI thing’ to stem the feared onslaught The age of extinction is supported by About this content

Leyland Cecco in Toronto

Thu 25 Jun 2020 01.30 EDT Last modified on Fri 26 Jun 2020 09.35 EDT

Asian hornet

An Asian hornet on the attack: the hornets have an insatiable taste for honeybees and are capable of destroying entire hives. Photograph: Eric Tourneret/Biosphoto/Avalon

It took Moufida and John Holubeshen just a day of tracing alleged sightings and studying map coordinates before the two amateur detectives found their target.

“We did the whole CSI thing,” says Moufida. “Plotting points and drawing lines, searching for where the middle of the circle – the nest – would be.”

The couple, like hundreds of other beekeepers in western Canada and the US, were hunting the Asian giant hornet, an invasive species whose stealthy advance throughout British Columbia and Washington state is causing growing unease.

Scientists and apiarists fear that, if permitted to spread unchecked, the hornets, which feast on honeybee larvae, could have disastrous consequences for tens of thousands of hives.

dead Asian giant hornet

Facebook Twitter Pinterest A dead Asian giant hornet brought from Japan for research purposes. Photograph: Elaine Thompson/AP

The couple’s investigation began last September, when word spread that hornets had been spotted on the outskirts of the city of Nanaimo where they live. Concerned for the safety of their four hives, they set out one evening towards the suspected nest location in a city park.

As they walked along the trail, they heard a low, rumbling buzz overhead. Moments later John felt a sharp pain in his chest. He had just become one of the first people to be stung by a giant hornet in North America.

“It was like being hit by a two-by-four,” he says. “It felt more like a bruised rib than a sting.”

They fled the scene – but soon realised they would have to return. “My first thought was I’ve got to go back and get a sample or a photo because nobody’s going to believe us,” he says. “It just seemed so surreal.”

As the hornet continues to spread into the Pacific northwest, government officials and local beekeepers have swapped tending hives for sleuthing: experimenting with homemade contraptions and deploying sophisticated electronics to trace the hornet’s spread – and hoping to save hundreds of thousands of honeybees in the process.

Beekeepers in Nanaimo destroy a giant hornets’ nest in September 2019.

Facebook Twitter Pinterest Beekeepers in Nanaimo destroy a giant hornets’ underground nest in September 2019. Photograph: Courtesy of John Holubeshen

Since the first hornet was spotted, British Columbia’s chief beekeeper, Paul van Westerndorp, has been keeping a growing list of sightings. So far, the hornets have been seen in the cities of Nanaimo, White Rock and Langley.

He is well aware of the threat they pose, but still Van Westerndorp holds a deep admiration for his adversary. “I look at this animal closely and it’s fascinating. Of course, beauty is in the eye of the beholder – but it’s an incredible piece of engineering,” he says.

The Asian giant hornet, Vespa mandarinia, is built to dominate an ecosystem: its massive orange head is equipped with sharp jaws to slice through prey. When its wings flap, they sound more like a hummingbird than a wasp.

After their encounter in the park, the Holubeshens returned to the nest later that night, accompanied by entomologist Conrad Bérubé and Peter Lange, president of the local beekeepers’ club. Bérubé eradicated the subterranean hive, receiving several painful stings through his protective layers in the process.

But while the Nanaimo beachhead was successfully destroyed, the hornets’ incursion continues.

“It’s like seeing an incoming storm and battening down the hatches. But we don’t know how strong these winds are going to be,” says Susan Cormier, who, with her partner, keeps 17 hives containing about 850,000 honeybees.

Two months ago, a giant hornet was spotted nine blocks from their home in Langley, British Columbia – a city near the US border. “We’re trying our best not to panic.”

Inside the giant hornets’ nest

Facebook Twitter Pinterest Inside the giant hornets’ nest destroyed in Nanaimo. Photograph: Courtesy of John Holubeshen

Genetic analysis of captured hornets suggests at least one came from South Korea, another from Japan. Until August 2019, no specimen had ever been spotted in Canada. And nearly a year later, no one is quite sure how they made the journey across the Pacific.

Most freight shipped across the Pacific is fumigated with carbon dioxide upon arrival to kill insects. But some cargo, such as automobiles, could provide refuge, says Van Westendorp. Others believe the hornets arrive as stowaways in oil tankers or in shipments of flower pots.

They stand at the entrance of a colony and create massive panic, slicing at the bees with their huge mandibles Paul van Westerndorp, chief beekeeper

“All it needs is a tiny little space, essentially the size of its body,” says Moufida.

As the sightings have increased across the region, the media has stoked fear over an impending “murder hornet” invasion. The hornet has been known to kill people with its venom, but experts agree that the risk to the human population is low. “Most negative interactions are from people unwittingly stepping on the nests – not predatory attacks,” says Van Westendorp.

While the hornets pose relatively little threat to humans, they have an insatiable appetite for honeybees and are capable of destroying entire hives.

As summer nears, more drone hornets are expected to emerge from the subterranean nests. Scouts are dispatched to look for bee colonies, marking their location with a distinct pheromone before returning with an assault party, often weeks later.

An Asian giant hornet next to a native bald-faced hornet.

Facebook Twitter Pinterest An Asian giant hornet next to a native bald-faced hornet. Photograph: Elaine Thompson/AFP via Getty Images

The tactics are ruthlessly efficient: a group of 30 hornets can decapitate tens of thousands of bees in only a few hours.

“They stand at the entrance and create a massive panic in that colony, slicing the bees with their huge mandibles,” says Van Westerndorp. Amid the panic, hornets will enter the nest and pull out honeybee broods to take home as “meatballs”.

Japanese honeybees have developed a defence, vibrating their bodies as they pile on to the invading hornet to cook it alive. But honeybees in North America are defenceless.

To prevent a massacre, plans have been forged months in advance. Queen hornets briefly emerge in spring to find a nesting site, providing a narrow window in which they can be trapped, thereby preventing the development of a full-on nest.

This spring, however, none of the sticky glue traps laid out by the province and beekeeping clubs worked, says Van Westerndorp.

Still, scientists in British Columbia remain optimistic. They are using bottle traps in the hope of catching live specimens which will be tagged with small radio transmitters and followed back to the nest which can then be eradicated. Other plans include fastening a bright, thin strip of plastic ribbon to the torso of a hornet, letting the shimmering material guide beekeepers back to the nest.

US beekeepers are also looking into infrared cameras that can detect the hornet. The idea has potential, says Van Westerndorp, but he admits the technology is so far “unproven”.

Asian hornet

Facebook Twitter Pinterest With its enormous mandibles, the Asian hornet is a formidable predator. Photograph: Eric Tourneret/Biosphoto/Avalon

Instead, beekeepers have started using low-tech approaches, modifying their hives in preparation for the summer.

“My husband has been building little screened entrances in front of our hives to try to prevent the hornets from getting in, but still allow the bees to get out,” says Cormier. “The problem is, we can’t find accurate information on how fat the Asian giant hornet is. How long is it? How big of a hole can it get into?”

For scientists and beekeepers alike, the big question is: how bad will the onslaught be?

“Maybe we’ll keep them down to a dull roar. Maybe they’ll be one of those invasive species that absolutely loves Canada and our ecosystem,” Cormier says, acknowledging the unfolding invasion is defined more by uncertainty than fear. “But nature is bigger than us. So we’ll just do what we can.”

Find more age of extinction coverage here, and follow biodiversity reporters Phoebe Weston and Patrick Greenfield on Twitter for all the latest news and features

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Fixing our global agricultural system to prevent the next COVID-19

Frédéric Baudron, Florian LiégeoisFirst Published June 5, 2020 Research Article https://doi.org/10.1177/0030727020931122

Article has an altmetric score of 53


While the world’s attention is focused on controlling COVID-19, evidence points at the biodiversity crisis as a leading factor in its emergence, and the outbreak of many past emerging infectious diseases. Agriculture is a major driver of biodiversity loss globally. Feeding a growing human population in ways that minimize harm to biodiversity is thus imperative to prevent the next COVID-19. Solutions exist, but the burden of implementing them should not be left to farmers alone, who are mainly small-scale family farmers. Supportive policies and markets are needed, but unlikely to bring about the required changes alone. A global concerted effort similar to the Paris Agreement for climate is probably required.Keywords Emerging infectious diseases, biodiversity, farming, land sparing, land sharing, ecosystem services


Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi (Anderson et al., 1991). The most recent, COVID-19, is caused by the SARS-CoV-2, a virus that belongs to the Coronaviridae family, and has spread across the globe in about 2 months from its origin in China, infecting people and claiming lives at an exponential rate, and leading to measures that are disrupting the global economy in an attempt to contain it (Hellewell et al., 2020; McKibbin and Fernando, 2020; Ramelli and Wagner, 2020; Sohrabi et al., 2020). Outbreaks of infectious diseases are on the rise (Smith et al., 2014). Most are zoonotic (60% of 335 infectious disease outbreaks that occurred between 1940 and 2004), meaning that they are spread from animals to humans, and the majority of these zoonoses (72% of the zoonoses that occurred between 1940 and 2004) originates from wildlife (Jones et al., 2008). COVID-19 is just the last in a long list of zoonoses originating from wildlife species (Zhou et al., 2020). In the past 20 years only, humanity was hit by three coronaviruses (SARS-CoV-1, 2003, Li et al., 2005; MERS-CoV, 2012, Zumla et al., 2015, SARS-CoV-2, 2019, Sohrabi et al., 2020), one influenza virus (Swine flu, 2009, Borkenhagen et al., 2019), two arboviruses (Chikungunya virus, 2005, Sam et al., 2015; Zika virus, 2015, Metsky et al., 2017) and one filovirus (Ebola virus, 2014 and 2018, Bourgarel and Liégeois, 2019). When in 2017, it was demonstrated that SARS-CoV-1 may have emerged through recombination among different virus strains in a single bat population in a cave in Southern China, the authors of the paper warned that “the risk of spillover into people and emergence of a disease similar to SARS is possible” (Hu et al., 2017). This indeed reads like a forecast of SARS-CoV-2 and the current COVID-19 pandemic….

So why do we see more cases of pathogens crossing from wildlife to humans? Several lines of evidence point to the current biodiversity crisis—which can be qualified as mass extinction (Barnosky et al., 2011)—as one of the primary causes. Land use change has been the leading driver in the emergence of zoonoses caused by a pathogen with a wildlife origin between 1940 and 2004 (Figure 1). The link between deforestation and these events has been established both theoretically (Faust et al., 2018), as well as empirically in a number of cases, including the emergence of Mycobacterium ulcerans and the recent outbreak of Ebola (Morris et al., 2016; Olivero et al., 2017). First, deforestation brings wildlife and people (and their livestock) into greater contact, increasing the risk of spillover (Morse et al., 2012). The fact that 70% of forests are within 1 km of a forest edge (Haddad et al., 2015) illustrates how pervasive ecotones, where wildlife, people and livestock interact, are. Second, species that survive (or thrive) during deforestation tend to be less sensitive to human disturbance (opportunistic/generalist species), and thus the ones most able to transmit pathogens to humans (or their livestock) (Johnson et al., 2020; Keesing et al., 2010).

Figure 1. Most commonly cited driver associated with 145 events of zoonotic emerging infectious diseases caused by a pathogen with a wildlife origin between 1940 and 2004 (from data published by Jones et al., 2008). “Land use changes” generally refer to changes in cropping practices and “agricultural industry changes” generally refers to changes in livestock husbandry. Together, they represent more than a third of all events.

Finally, pathogens may be more prevalent in animal communities with reduced diversity. Diverse host communities tend to include less competent reservoir species for any given pathogen, lowering prevalence and risk of spillover (to humans or livestock), a phenomenon known as the “dilution effect” (Ostfeld, 2009). Trophic downgrading—the extirpation of apex consumers through human activities (Estes et al., 2011)—is less visible and quantifiable than deforestation, but can lead to similar changes in wildlife communities with ripple effects on a number of ecosystem processes including disease dynamics (Dirzo et al., 2014). For example, the continuing emergence of Lyme disease in North America has been attributed to the decline of the red fox, leading to an increase in the abundance of small mammal hosts of the pathogen (Levi et al., 2012). Extirpation of lions and leopards in parts of Ghana led to an increased abundance of baboons coming more frequently into contact with people, with high transmission risk of intestinal parasites (Ryan et al., 2012; Taylor et al., 2016). In India, the increasing number of human cases of rabies has been linked to the decline of vultures (Markandya et al., 2008).

Once biodiversity changes have altered the dynamics of pathogen transmission, the likelihood of spillover to humans is high. Indeed, humans are one of the most abundant vertebrates worldwide, representing 36% of the global biomass of mammals (Bar-On et al., 2018), and we interact with almost every ecosystem around the world (Ellis and Ramankutty, 2008). This risk is, of course, increased by practices such as bush meat consumption (Wolfe et al., 2005). Yet at the same time, bushmeat represents a critical source of quality protein and readily available micronutrients with few alternatives for millions of people in tropical countries (Fa et al., 2003; Golden et al., 2011). Rodents and bats are often the origin of zoonoses caused by a pathogen with a wildlife origin (Figure 2; bats are for example known reservoirs of SARS-like coronaviruses; Hu et al., 2017), simply because these two orders represent more than 60% of all mammal species (Burgin et al., 2018) while pathogen richness tends to correlate with host species richness (Mollentze and Streicker, 2020). Many zoonotic pathogens may then be transmitted to humans directly from these reservoirs (e.g., Ebola, Olivero et al., 2017) or through another intermediate wild host (e.g., SARS, for which the palm masked civet was likely and intermediate host between bats and humans; Li et al., 2005). For many others, however, livestock is an intermediate host (Figure 2). Livestock and poultry are indeed very abundant vertebrates worldwide, representing 60% of the global biomass of mammals and 70% of the global biomass of birds, respectively (Bar-On et al., 2018), and have accompanied human in most ecosystems around the world (Gilbert et al., 2018). Livestock—particularly when kept in industrial operations where large numbers of animals of low genetic diversity are confined—may amplify pathogens and provide them with an opportunity to mutate and become transmissible to humans (Jones et al., 2013). Change in livestock husbandry has been an important driver in the emergence of zoonoses caused by a pathogen with a wildlife origin between 1940 and 2004 (Figure 1). Industrial poultry farming played a major role in the outbreak of the H5N1 avian influenza (Graham et al., 2008). The recent outbreak of Middle East respiratory syndrome (which is caused by a coronavirus, similarly to COVID-19) is thought to have crossed from bats to humans, with camels as an intermediate “stepping stone” (Zumla et al., 2015).

Figure 2. Sum of zoonotic viruses carried by most common livestock and pet mammal species compared to the wild mammal species with the highest sums in the orders Rodentia, Chiroptera, Primates, Artiodactyla and Carnivora (two species per order, from data published by Johnson et al., 2020).

Safeguarding biodiversity thus appears essential to prevent future pandemic zoonotic diseases. In a 2017 article of Nature that followed the publication of evidence suggesting that SARS-CoV-1 emerged from a bat colony in Southern China, Professor Kwok-Yung Yuen—one of the co-discoverer of the SARS coronavirus—warned that to prevent the emergence of another SARS-like zoonosis “we should not disturb wildlife habitats and never put wild animals into markets” (Cyranoski, 2017). If overexploitation remains a leading threat, agriculture was found to be one of the “biggest killers” for 62% of the species listed as threatened or nearly threatened (Maxwell et al., 2016) (crop farming was found to threaten 54% of these species and livestock farming 26%). About 22% of the land area represented by Biodiversity Hotspots is threatened by agricultural expansion (Veach et al., 2017). Furthermore, these areas often overlap with emerging disease “hotspots” (Jones et al., 2008). Agricultural expansion, as well as agricultural intensification, are major drivers of biodiversity loss (Baudron and Giller, 2014; Foley et al., 2011; Kehoe et al., 2017). Feeding a growing human population in ways that minimize harm to biodiversity is thus imperative, and core to achieving the “World we Want” (UN General Assembly, 2015).

Norman Borlaug—wheat scientist, “Father of the Green Revolution” and recipient of the Nobel Peace Prize in 1970—argued that agricultural intensification does just that: sparing land for nature (Borlaug, 2007). If crop yields had remained at their 1961 levels, India would have required 19.9 million ha of additional land to reach the amount of maize produced in 2018 and 87.6 million ha of additional land for its wheat production in 2018 (Figure 3). Mexico would have similarly required a substantial amount of additional land, likely through conversion of nature to farmland (22.2 million ha for maize and 1.2 million ha for wheat; Figure 3). Spared areas are smaller in countries largely bypassed by the Green Revolution, such as Kenya, but still substantial (1.1 million ha for maize, and 0.2 million ha for wheat; Figure 3). Several publications have demonstrated that maximizing crop yields and thereby limiting the total area under agriculture—an approach known as “the Borlaug hypothesis” or “land sparing”—could be our best option to minimize trade-offs between agriculture and biodiversity (Balmford et al., 2019; Phalan et al., 2011). Recommending to segregate biodiversity and agriculture (and other human activities) is indeed tempting to reduce the risk of emerging zoonoses (Marco et al., 2020).

Figure 3. Comparison of actual land and land that has been theoretically spared by yield increase (i.e., additional land that would have been needed if yields had remained at their 1961 levels) for maize and wheat in India, Mexico and Kenya (source: FAOSTAT).

Land sparing however, suffers from at least two major weaknesses. First, maximizing yields implies the use of large quantities of agricultural inputs, often impacting a larger area than merely the land farmed intensively. When large rates of nutrients (e.g., nitrates and phosphates) and pesticides are used, they may be transported for thousands of kilometers downstream and downwind (Carpenter et al., 1998; Gordon et al., 2008; Hoferkamp et al., 2010; Smith et al., 1999). Second, maximizing yields is often accompanied by extreme simplification of agroecosystems and loss of farmland biodiversity. This may reduce ecosystem disservices—such as the risk of zoonosis emergence—but it also cuts farmers from vital ecosystem services, including soil fertility maintenance, pest control and regulation of microclimate (Kebede et al., 2018; Sida et al., 2019; Yang et al., 2020). Ecosystem services provided by biodiversity may have far reaching impacts on human well-being, including improved diets (Baudron et al., 2019b). Indeed, such services are particularly crucial to family farmers in developing countries (as in the examples given), as they use insignificant quantities of external input and often cannot afford them. They are often qualified as being “organic by default”—but still produce more than half of the food consumed globally through processes supported by nature (Tittonell et al., 2016). Ecosystem services are also important for the sustainability of other—more intensive—production systems as well, as they also depend on ecosystem services as highlighted by a recent FAO report (FAO, 2019). The urgency to maintain ecosystem services to sustain the global food system is epitomized by the increase in soil degradation and in pesticide use (illustrating the decline of pest biocontrol), and by the decline of pollinators worldwide (Garibaldi et al., 2009; Oldeman, 1994; Wilson and Tisdell, 2001).

In response to these issues, and at the opposite side of the spectrum of solutions to minimize trade-offs between agriculture and biodiversity is “land sharing” (Clough et al., 2011; Perfecto and Vandermeer, 2010; Wright et al., 2012). It is based on a land-use model that integrates (rather than segregates) production and biodiversity on the same land units, by minimizing the use of external inputs and retaining patches of natural habitat within farmlands. Land sharing, however, also suffers from at least two major weaknesses. First, low-input agriculture generally achieves yields inferior to those achieved by intensive farming, and thus consumes more space—likely taken away from nature—to meet any production target (Green et al., 2005). Second, agriculture can rarely be sustained without some degree of external inputs. For instance, some nutrient inputs are needed to at least compensate nutrients exported in harvest (Vitousek et al., 2009). In addition, crop losses due to pests tend to be severe and pesticide-free farming can only be achieved in rare situations (Lucchi and Benelli, 2018; Oerke, 2006).

Ultimately, principles from both land sparing and land sharing will be part of the required solution: inputs are needed, but their spill-over needs to be managed (through e.g. conservation agriculture and precision farming); efforts to increase productivity need to be balanced with the need to retain ecosystem services; and using a landscape approach, as ecological flows of energy, materials (e.g., soil, water) and organisms (e.g., natural enemies, pollinators, species of concern to conservation) are best understood and managed at landscape-level, not at plot-level (Baudron and Giller, 2014). A landscape approach to reduce tradeoffs between farming and biodiversity involves “targeted sparing,” in biodiversity hotspots only, and only to the degree necessary for maintaining critical wildlife habitats (e.g., habitat of species with restricted range; Folberth et al., 2020). In areas where the opportunity cost of taking land away from production is high, such targeted sparing should center on the establishment of networks of small natural or semi-natural areas across the landscape rather than large contiguous conservation areas (Maes et al., 2015). These networks should however cover the range of abiotic conditions in the landscape, including some highly productive land, for biodiversity to be effectively conserved (Fischer et al., 2006). It is also beneficiary for the network to include critical transition zones (e.g., riparian areas, mangroves), due to the critical role they play as conduits for materials and organisms between adjacent ecosystems (Ewel et al., 2001). In addition to be feeding and breeding grounds, as well as dispersal corridors, for many species, they provide critical ecosystem services including the regulation of water flow, and the trapping and transformation of sediments, nutrients and pollutants (Levin et al., 2001; Richardson et al., 2007). The role multifunctional landscapes can play in both conserving biodiversity and feeding people now and in the future is increasingly recognized (Kremen and Merenlender, 2018). Southern Ethiopia offers an example of such a multifunctional landscape that hosts high biodiversity while being more productive than simpler landscapes (Baudron et al., 2019a). This multifunctional landscape of Southern Ethiopia is also more sustainable and resilient (Duriaux Chavarría et al., 2018), provide more diverse diets (Baudron et al., 2017) and produce staple food with higher nutritional content (Wood et al., 2018).

Current policies and markets, however, tend to impede multifunctional landscapes, and to promote instead simplified agricultural landscapes depleted in biodiversity, highly dependent on external inputs and susceptible to shocks and stresses. Promoting “landscapes that work for nature and people” (Kremen and Merenlender, 2018) requires the removal of perverse policies such as subsidies and distortions, and their replacement by incentives that promote production systems that are less demanding of land and other natural resources (Mooney et al., 2005). Agricultural landscapes are also shaped by our consumption patterns. Consumers in developed countries (in particular) export biodiversity threats through their consumption of coffee, tea, chocolate, sugar, textiles, fish, etc (Lenzen et al., 2012). In order to promote consumption patterns that reduce impact on biodiversity, proper pricing, certification and labeling are required. The true costs and benefits to nature of agricultural practices need to be embodied in the prices of the corresponding commodities (Balmford et al., 2002). Environmental labels have a long history (e.g., organic produce, Protected Designation of Origin, Gracia and de-Magistris, 2016) and could be expanded to communicate impacts and benefits on nature to consumers, as an incentive to purchase more environmentally-friendly products. Consumption patterns that cause biodiversity loss tend to also be those causing unhealthy diets, one of today’s leading risk factors for mortality globally (Willett et al., 2019).

Yet supportive policies and markets alone are unlikely to bring about the required changes. A large share of the global food produced does not enter the market, but is consumed by the small-scale family farmers who produce it (Frelat et al., 2016). Reducing the negative impact of our agricultural systems on biodiversity will thus require a global, concerted effort similar to the Paris Agreements for climate. Although several high-profile reports have recently highlighted the importance of biodiversity for our very existence (FAO, 2019; HLPE, 2017; IPBES, 2019), raising public awareness of the consequences of the biodiversity crisis to the same intensity as awareness of the consequences of the climate crisis is critical (Legagneux et al., 2018). In a more-and-more connected world, we share joint responsibility for our global future. We must shoulder the burden of feeding humanity whist maintaining the very biodiversity that confers resilience on our increasingly cultivated planet against shocks such as the global pandemic of COVID-19.


We are grateful to Ken E. Giller and Bruno Gérard for their comments on an earlier version of the manuscript. We also thank an anonymous reviewer for his/her critical and constructive comments.

Author contributions
FB conceived the paper and wrote the first draft of the manuscript. FL contributed to the writing of the final manuscript

Declaration of conflicting interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Frédéric Baudron https://orcid.org/0000-0002-5648-2083


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Outlook on Agriculture

ISSN: 0030-7270
Online ISSN: 2043-6866
Copyright © 2020 by SAGE Publications

Presence of HLB vector detected in Spanish region of Cantabria

The Council of Rural Development, Livestock, Fishing, Food and Environment of Cantabria has warned of the presence in the region of the African citrus psila (Trioza erytreae), after an outbreak was detected in the town of Mogro, in the municipality of Miengo.

This sucking insect of sub-Saharan origin can affect lemons, oranges, mandarins and other citrus fruits, causing the quality and flavor of the fruit to deteriorate, and even the death of the affected tree in a few years. It was first detected in the Canary Islands in 2002 and in Galicia and northern Portugal in 2014 and it is a regulated quarantine pest in the European Union. It is an important vector of the bacterium that causes Huanglongbing (HLB) or citrus greening disease, as reported by the regional Executive in a press release.

In order to eradicate this first outbreak and prevent its spread, the Government of Cantabria will inspect the affected area and its surroundings to delimit its extension and will destroy the affected crops and subsequently burn or bury them. To this end, the General Directorate of Rural Development has asked for citizen collaboration. The Plant Production and Health section of the Council should be told about “the slightest suspicion” of the presence of the pest.

People have also been asked to facilitate the access of inspectors to private orchards and gardens, as they are the places where the different citrus varieties that exist in Cantabria are mostly located.

In case of any doubt or sighting, the technicians of the Plant Production and Health section can be contacted via phone (942 207 807) or email (sanidadvegetalcantabria@cantabria.es).

Source: europapress.es

Publication date: Wed 24 Jun 2020

Welcome to the 31st edition of ENDURE News, the electronic newsletter from ENDURE. Please feel free to share this newsletter with colleagues.

  • Report on glyphosate use in Europe demonstrates the diversity of uses and the dependence of some cropping systems on the herbicide
    Despite being the most widely used herbicide in the world and the subject of controversy regarding its direct and indirect effects, little information is available on the quantitative aspects of glyphosate, such as its use in European countries. This has now been addressed with the publication of an ENDURE report, ‘A survey on the uses of glyphosate in European countries’.
  • New group for chemical pesticide-free agriculture
    A new European Research Alliance has been launched, drawing together 24 research organisations from 16 countries focused on the topic ‘Towards a Chemical Pesticide-free Agriculture’. The Alliance includes eight ENDURE partner organisations and “aims to rethink the way research is carried out and develop new common research and experimentation strategies, not just at a national level, but throughout the whole continent”.
  • Learning in the virtual world
    Covid-19 has meant that we have all had to adapt our working practices, ensure social distancing and keep colleagues and family safe. For many of us it has seen a major increase in the use of online meetings and this has certainly been the case for Certiphyto’s world tour. The tour had barely kicked off in the French Caribbean (pictured right, a visit to an organic producer in Martinique) when France went into lockdown, bringing what should have been a 22-date tour to a rapid halt.
  • JKI launches IYPH programme
    Germany’s Julius Kühn-Institut (JKI) has identified a range of events it will target to mark the 2020 International Year of Plant Health. In particular, JKI will be driving home the message that the global trade in plants means there is a permanent risk of pests and diseases being introduced into regions where they are not indigenous.
  • Win-win with strip cropping, says WUR
    The multiple benefits of strip cropping are highlighted in a recent report from Wageningen University, which has been studying the approach for several years. This year more than 20 Dutch farmers, both conventional and organic, have begun or expanded strip cropping, which helps attract more beneficial insects into fields and slows disease spread.  
  • IWMPRAISE offers IWM inspiration
    IWMPRAISE, the Horizon 2020 project dedicated to Integrated Weed Management (IWM), has produced a series of ‘inspiration sheets’ over recent weeks. They present guidance on techniques such as inter-row hoeing in small grain cereals and improving crop diversification through the use of intercrops and subsidiary crops, alongside a series of inspiration sheets on the biology and management of a selection of weeds.
  • Insights into barriers to crop diversification
    DiverIMPACTS researchers have analysed the project’s 25 case studies to explore the extent to which barriers to crop diversification are related to the setting in which they emerge. The project’s multi-actor case studies are allocated to one of five clusters: service crops, crop diversification under adverse conditions, crop diversification in systems from Western Europe, diversification through intercropping, with a special focus on grain legumes, and the diversification of vegetable cropping systems.
  • LCA ‘limited’ in agroecology assessments
    The most commonly used method for analysing the environmental impacts of agricultural systems tends to overlook major factors such as biodiversity, soil quality, pesticide impacts and societal shifts, reports France’s National Research Institute for Agriculture, Food and the Environment (INRAE).
  • Farmers urged to share yield monitor data
    Researchers from the Horizon 2020 EcoStack project are urging farmers to share their yield monitor data from GPS-enabled combine harvesters. The data will be used to help researchers establish “how landscape features found just beyond the field affects variation in crop yield, and whether yield decline towards the edge of fields can be reduced by the presence of certain types of field boundaries”.
  • WUR to investigate wild potato potential
    Wageningen University & Research (WUR), ENDURE’s Dutch partner, is to turn its attention to wild potatoes in the search for resistance to a wide range of potato pests and diseases. WUR says pests and diseases in potato crops are likely to increase due to increasing extremes in temperature and rainfall combined with a reduction in chemical solutions.
  • Ensuring successful control strategies
    An international team of researchers lead by Rothamsted Research has examined the factors that make or break campaigns to stop invading plant pathogens, concluding that educating growers about the effectiveness of control strategies is more important than emphasising the risks posed by the disease.
  • Agroscope to lead Japanese beetle project
    Agroscope, ENDURE’s Swiss partner, is to lead a €5.5 million project to develop sustainable strategies for controlling the quarantine pest, Japanese beetle. The pest was first detected on Switzerland’s southern border in 2017 and it threatens to spread further into Switzerland and elsewhere in Europe.
  • EuroBlight unveils 2019 monitoring results
    EuroBlight, the international consortium tracking the spatial distribution of Phytophthora infestans, the pathogen responsible for late blight in potato crops, has published the results of its extensive 2019 survey work, revealing the distribution and diversity of dominant clones in the crop.
  • SusCrop newsletter now available
    The second newsletter from ERA-Net SusCrop is now available, bringing readers up to date with the activities of the Cofund Action under H2020, which “aims to strengthen the European Research Area (ERA) in the field of Sustainable Crop Production through enhanced cooperation and coordination of different national and regional research programmes”.
  • WUR unveils greenhouse of the future
    Wageningen University and Research (WUR) has unveiled a cutting-edge demonstration greenhouse designed to help the Dutch horticultural sector become CO2 neutral by 2040. Not limited simply to energy efficiency, the new greenhouse incorporates innovative measures designed to reduce pesticide and artificial fertiliser use to zero while improving yields.
  • Events calendar: Check it out!
    Inevitably, the Covid-19 pandemic has played havoc with this year’s conference and meeting schedules. Here at ENDURE we have updated our Events calendar as best we can to try and keep track of the conferences and meetings which have been rescheduled or moved online.
  • Update: SusCrop issues second call for proposals
    The second transnational call for proposals from ERA-Net SusCrop is now open with an extended deadline due to the impact of COVID-19 in many countries. SusCrop is an ERA-Net Cofund Action under H2020, which “aims to strengthen the European Research Area (ERA) in the field of Sustainable Crop Production through enhanced cooperation and coordination of different national and regional research programmes”.
  • System experiments: Take the survey!
    Are you involved in system experiments, whether at the project stage, ongoing or completed? If so and you can spare a few minutes, you can take part in a survey forming part of a PhD thesis focusing on ‘Methodological contributions to experimental and observational approaches in agronomy and agroecology’ being conducted by Sandrine Longis (a CIFRE Arvalis thesis in collaboration with INRAE’s Agroecologies, Innovations and Ruralities combined research unit (UMR AGIR)).
  • Goodbye INRA, hello INRAE
    France’s National Institute for Agricultural Research (INRA) is no more. Instead, it has undergone a major merger with the country’s National Institute for Research in Science and Technology for the Environment and Agriculture (IRSTEA). They new organisation is called the National Research Institute for Agriculture, Food and the Environment and will be known by the initials INRAE.
  • PhD to focus on pest modelling in rice
    France’s INRAE and CIRAD are offering a PhD focusing on modelling ‘multiple pests in rice crops for agroecological rice protection in Cambodia’. The PhD should help tackle the excessive use of pesticides in Cambodian rice crops, where up to 13 treatments are used each cropping season, leading to some European exports being refused because of excess residues.
  • To find out more about ENDURE, visit: www.endure-network.eu
  • To get in touch with ENDURE, use the contact form
  • Click here to unsubscribe from this newsletter

Info on locusts

Global Food for Thought



Locusts Vary: The locusts currently in South America are different than the Desert Locusts plaguing Eastern Africa, the Middle East, and South Asia. “Locust” refers to insects in the family Acrididae, which includes long-horned grasshoppers and crickets. The migratory locust has the widest range, spanning from New Zealand to the African continent, but many localized species abound, such as the Rocky Mountain locust, Italian and Moroccan locusts, and red and brown locusts in South Africa.


Bubble-blowing drones may one day aid artificial pollination

Flying machines could step in when bees and other insects are scarce, researchers say

drone pollinating flower with bubbles
Drones that blow bubbles to delicately deliver pollen to flowers (a peach-leaved bellflower, pictured) could help make up for dwindling populations of natural pollinators, like bees, researchers say. E. Miyako

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By Maria Temming

June 22, 2020 at 10:15 am

Drones that blow pollen-laden bubbles onto blossoms could someday help farmers pollinate their crops.

Rather than relying on bees and other pollinating insects — which are dwindling worldwide as a result of climate change (SN: 7/9/15), pesticide use (SN: 10/5/17) and other factors — farmers can spray or swab pollen onto crops themselves. But machine-blown plumes can waste many grains of pollen, and manually brushing pollen onto plants is labor-intensive.

Materials chemist Eijiro Miyako of the Japan Advanced Institute of Science and Technology in Nomi imagines outsourcing pollination to automatous drones that deliver pollen grains to individual flowers. His original idea involved a pollen-coated drone rubbing grains onto flowers, but that treatment damaged the blossoms (SN: 3/7/17). Then, while blowing bubbles with his son, Miyako realized that bubbles might be a gentler means of delivery. 

To that end, Miyako and his colleague Xi Yang, an environmental scientist also at JAIST, devised a pollen-containing solution that a drone toting a bubble gun could blow onto crops. To test the viability of their pollen-loaded bubbles, the researchers used this technique to pollinate by hand pear trees in an orchard. Those trees bore about as much fruit as trees pollinated using a traditional method of hand pollination, the researchers report online June 17 in iScience.

Among various commercially available bubble solutions, Miyako and Yang found that pollen grains remained most healthy and viable in one made with lauramidopropyl betaine — a chemical used in cosmetics and personal care products. Using that solution as their base, the researchers added pollen-protecting ingredients, like calcium and potassium, along with a polymer to make the bubbles sturdy enough to withstand winds generated by drone propellers.

The researchers blew pollen bubbles at flowers on three pear trees in an orchard. On average, 95 percent of the 50 pollinated blossoms on each tree formed fruits. That was comparable to another set of three similar trees pollinated by hand with a standard pollen brush. Only about 58 percent of flowers on three trees that relied on insects and wind to deliver pollen bore fruit.

To test the feasibility of applying this bubble treatment with flying robots, Miyako and Yang armed a drone with a bubble gun and blew pollen bubbles at fake lilies while flying by at two meters per second. More than 90 percent of the lilies were hit with bubbles, but many more bubbles missed the blooms. Making drone pollination practical would require flying robots that can recognize flowers and deftly target specific blossoms, the researchers say.

Not everyone is convinced that building robotic pollinators is a good idea. Simon Potts, a sustainable land management researcher at the University of Reading in England, sees this technology as a “piece of smart engineering being shoehorned to solve a problem which can be solved in … more effective and sustainable ways.”

In 2018, Potts and colleagues published a study in Science of the Total Environment, arguing that protecting natural pollinators is a better way to safeguard plant pollination than building robotic bees. Insects, the researchers noted, are more adept pollinators than any machine and don’t disrupt existing ecosystems. Miyako and Yang say their bubble solution was biocompatible, but Potts worries that dousing flowers in human-made substances could dissuade insects from visiting those trees.  

Roboticist Yu Gu of West Virginia University in Morgantown, who designs robotic pollinators but was not involved in the new work, says that building robotic bees and supporting insect populations are not mutually exclusive. “We’re not hoping to take over for bees, or any other natural pollinator,” he says. “What we’re trying to do is complement them.” Where there is a shortage of winged workers to pollinate crops, farmers could one day use robots “as a Plan B,” he says. No pun intended.

Questions or comments on this article? E-mail us at feedback@sciencenews.org


X. Yang and E. Miyako. Soap bubble pollination. iScience. Published online June 17, 2020. doi: 10.1016/j.isci.2020.101188.

S.G. Potts et al. Robotic bees for crop pollination: Why drones cannot replace biodiversity. Science of the Total Environment. Vol. 642, November 15, 2018, p. 665. doi: 10.1016/j.scitotenv.2018.06.114.

Maria Temming

About Maria Temming

Maria Temming is the staff reporter for physical sciences, covering everything from chemistry to computer science and cosmology. She has bachelor’s degrees in physics and English, and a master’s in science writing.

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Countries start trials of biological pesticide to fight desert locusts

Wednesday June 24 2020

A volunteer sprays pesticide at a hatch site in Isiolo County, Kenya, where millions of locust nymphs hatched in February. PHOTO | FILE | NMG 


In Summary

  • Thousands of hectares of farmland have been damaged by locusts in Kenya, Uganda, Ethiopia, Somalia, South Sudan, Djibouti and Eritrea.


More by this Author

Countries devastated by desert locusts in East Africa have begun trials on the effectiveness of a bio-control pesticide against the hoppers even as the Food and Agriculture Organisation (FAO) warns that bigger swarms are gaining momentum in one of the worst infestations in the region yet.

The FAO has started trials of the fungi-based bio-control called Metharizium acridum, known by brand name Green Muscle, in parts of Kenya, and Ethiopia. Somalia, which previously did not have any control efforts, already started using the bio-control pesticide last.

Samples of the product have also been sent to Pakistan and India where the locust situation is getting worse.

Green Muscle joins previous control operations that have included aerial and ground spraying of affected areas with pesticides using ultra Low volume chemical formulations Malathion and Fenitrothion.

Kenya Permanent Secretary for Agriculture Prof Hamadi Iddi Boga, told The EastAfrican the product has proved to work better than chemicals “provided it is applied on time to hopper bands before swarming starts. This is a biological product as opposed to a chemical pesticide where you use an organism to kill another.”

A bio-control pesticide is a biological weapon which only kills the target insect without affecting non-target insects, the environment and human health.

Related Stories

Already, tens of thousands of hectares of farmland and pasture have been damaged by locusts in Kenya, Uganda, Ethiopia, Somalia, South Sudan, Djibouti and Eritrea.


“This outbreak could not only threaten the livelihoods and food security of residents, but the respective countries’ economies as well,” FAO one of the principal agencies leading the fight against the desert locust crisis has warned.

It is hoped the newly introduced bio-pesticide based on a specific isolate of Metarhizium acridum fungus which only attacks locusts and grasshoppers, effectively stopping them in their tracks will be more effective.

Metarhizium acridum has been found to be effective against locusts and has been developed into a biological control pesticide. We are using fungi to kill the locusts. The fungus is specific to locust and the grasshopper class of insects. It is most effective when used against the locusts at the hopper stage,” explained Prof Boga.


“It invades the hopper’s system and when they are infected they start infecting each other because the hoppers always band together and don’t move very far. So it infects them and then you can come back and monitor to see if it has been effective,” he added.

“It infects the hoppers and causes them to die within five days. It has been our wish to move away from chemical insecticides and this presents as an alternative,” he said. It works against the locusts at the hopper stage.

He said the ministry had been seeking an environment-friendly pesticide which had not been available until now.

He said unlike the chemical pesticides in use elsewhere, once the fungi infects the locusts it continues to multiply amongst the other locusts, making it more cost-effective as an exterminator.

“If the fungi are able to multiply in the environment, then this is going to be very good,” he said. But noted that they were eager to see what the results will be, given that the areas the bio-control weapon was being tested were too hot and it is unknown how they would react to the environment.


The product known by the trade name Green Muscle and manufactured by Éléphant Vert, stems from a programme called LUBILOSA “LUtte BIologique contre les Locustes et Sauteriaux”, (biological control of locusts and grasshoppers), which was funded by the governments of Canada, the Netherlands, Switzerland, Britain and the USA.

In 2009, the FAO reported that the product, had effectively treated 10,000 hectares of Red Locust-infested land in Tanzania and again to great effect in Madagascar.

The Centre for Agriculture and Bioscience International (CABI) has also been part of the multi-agency response to the locust problem in countries including Kenya, which is said to be suffering the worst infestation in 70 years. CABI said research has confirmed that Green Muscle is effective against various species including desert locusts. Advertisement

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Crop pathogens are more adaptable than previously thought

June 23, 2020 8.20am EDT


  1. Antonis Rokas Cornelius Vanderbilt Chair in Biological Sciences, Professor of Biological Sciences and Biomedical Informatics, and Director of the Vanderbilt Evolutionary Studies Initiative, Vanderbilt University

Disclosure statement

Antonis Rokas and his laboratory receive or have received funding from the National Science Foundation, the John Simon Guggenheim Memorial Foundation, the Burroughs Wellcome Trust, the National Institutes of Health, the Beckman Scholars Program, the March of Dimes, the Howard Hughes Medical Institute, and Vanderbilt University.


Vanderbilt University

Vanderbilt University provides funding as a founding partner of The Conversation US.

The Research Brief is a short take about interesting academic work.

The big idea

Many of the pathogens threatening the world’s major crops and food security are either fungi or fungus-like organisms known as oomycetes. In a recent study published in the journal Nature Communications, researchers found that these microorganisms have the ability to rapidly adapt to environmental conditions and to the plant hosts they infect. This finding adds to growing concerns around these types of pathogens, which could become harder to control in both agriculture and forestry.

Potato infected with the oomycete Phytophthora infestans. This oomycete was the cause of the Irish potato famine that led to the starvation and death of more than 1 million people in the 19th century. Phytophthora infections cause annual damages that amount to billions of U.S. dollars. Wikipedia

To understand why only certain organisms are pathogens and others are not, ecologists like to think of each organism’s lifestyle or “ecological niche.” An organism’s niche is a space defined by its relationship to other organisms, such as the host organisms it interacts with, and preferred environmental conditions, such as temperature and humidity. For example, the oomycete Phytophthora infestans that causes potato late blight thrives at lower temperatures, around 15 degrees Celsius, whereas Botryosphaeria fungi causing apple “bot rots” prefer temperatures around or above 25°C.

While the ecological niches of many plant and animal pathogens are well understood, this is not the case for microbial pathogens, such as fungi and oomycetes. To begin filling this gap, the new study synthesized and analyzed temperature and host plant range data from hundreds of fungal and oomycete pathogens.

The researchers found that although some pathogens infect just one or a few plant hosts, others infect a broad range. The same was true of temperature; some pathogens can grow in a broad range of temperatures, while others thrive in only a narrow range. Simply put, there’s not one pathogen lifestyle; rather, any lifestyle could be that of a pathogen.

But an even bigger surprise came when the researchers discovered that the two traits, temperature range and plant host range, did not correlate with one another. Thus, crop pathogen lifestyles cannot easily be grouped into general categories, such as generalists that grow in a wide range of temperatures and infect many plant hosts, and specialists, which is the opposite. What’s more, the new study found that both temperature range and plant host range change rapidly during evolution.

Why it matters

Rice infected with the rice blast fungus Magnaporthe grisea. Annually, rice blast destroys a quantity of rice that could feed 60 million people. Wikipedia, CC BY-SA

Knowledge that crop pathogens exhibit diverse ecological lifestyles and evolve rapidly is decidedly not good news for our crops and global food security. On a planet where the climate is changing, highly adaptable pathogens are likely to be harder to control. In addition, much of the world relies on an outdated system of agriculture that favors monoculture and reliance on fungicides to which pathogens quickly evolve resistance. This combination make for a deadly mix, with new outbreaks of emerging plant diseases on the rise.

What still isn’t known

We still know little about the ecological niches of microbes. Examining host range and temperature, two important traits to the lifestyles of crop pathogens, is but the first step. In the future, researchers will need to examine additional facets of the ecological niches of these pathogens, such as humidity or competition with other organisms, which will be key for understanding why some microbes are pathogens and others are innocuous.

Copyright © 2010–2020, The Conversation US, Inc.

Temperate insects as vulnerable to climate change as tropical species

Date: June 8, 2020 Source: Uppsala University Summary: In previous research, it has been assumed that insects in temperate regions would cope well with or even benefit from a warmer climate. Not so, according to researchers. The earlier models failed to take into account the fact that insects in temperate habitats are inactive for much of the year. Share: FULL STORY

In previous research, it has been assumed that insects in temperate regions would cope well with or even benefit from a warmer climate. Not so, according to researchers from the Universities of Uppsala and Lund in Sweden and Oviedo, Spain, in a new study. The earlier models failed to take into account the fact that insects in temperate habitats are inactive for much of the year.

The research group’s study, published in the journal Scientific Reports, presents new knowledge about the potential effects of global warming on insect populations. The results show that insects may be more threatened by climate change than previous estimates have indicated.

“Insects in temperate zones might be as threatened by climate change as those in the tropics,” says Uppsala University professor Frank Johansson.

The researchers found new, disturbing patterns in a modified analysis of a previously used dataset on insects’ critical temperature limits and their survival. Their conclusion is that temperate insects might be just as sensitive to climate change as tropical ones. The previous studies showed that tropical insects are severely threatened by climate change since they already live very close to their optimal temperature and “critical thermal maximum.” However, the scientists responsible for those previous studies also assumed that temperate insects live far below their own optimal and maximum temperatures, and might therefore benefit from climate change.

The problem is that the earlier studies used mean annual temperatures for all their estimates. In so doing, they failed to consider that the vast majority of insects in temperate latitudes remain inactive in cold periods — that is, for much of the year.

When more biological details about the various insect species, and only the months in which the species are active, are entered in the models, the new estimates show that in temperate insects’ habitats, too, the temperatures are close to the insects’ optimal and critical maximum. This is because the average temperature for the months when the insects are active clearly exceeds the mean year-round temperature. Temperate insects are thus as vulnerable as tropical species to temperature increases

When the temperature is close to insects’ optimal temperature or critical upper limit, there is a great risk of their numbers declining. The decreases in insect populations would also affect humans, since many insect species provide ecosystem services, such as pollination of fruit, vegetables and other plants we eat.

Story Source:

Materials provided by Uppsala University. Original written by Linda Koffmar. Note: Content may be edited for style and length.

Journal Reference:

  1. Frank Johansson, Germán Orizaola, Viktor Nilsson-Örtman. Temperate insects with narrow seasonal activity periods can be as vulnerable to climate change as tropical insect  species. Scientific Reports, 2020; 10 (1) DOI: 10.1038/s41598-020-65608-7


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Receive a Daily or Weekly summary of the most important articles direct to your inbox, just enter your email below: Banana tree showing signs of Fusarium wilt (Panama disease). Credit: Scot Nelson (CC0 1.0). GUEST POSTS 8 June 2020 16:00

Guest post: How climate change could accelerate the threat of crop diseases

Dr Helen Fones

08.06.2020 | 4:00pmGuest postsGuest post: How climate change could accelerate the threat of crop diseases

This guest post is by:

Dr Helen Fones, plant pathologist and UKRI Future Leaders fellow at the University of Exeter.

As the global population has increased, humankind has placed increased demands on the planet for land, food and water. Agricultural practice has intensified, but, despite this, two billion of the almost eight billion people on Earth still experienced food insecurity in 2019

While food insecurity stems from a mix of political, economic and agricultural causes, climate change also poses a number of threats. For example, increasing temperatures may alter the suitability of regions for particular crops, and extreme weather events may have severe and unpredictable effects upon harvests. 

Climate also influences the spread of pests and pathogens, which can diminish and decimate yields, and whose suppression is a permanent battleground in agriculture.

In a review paper, published in Nature Food, my colleagues at the University of Exeter and I explore the potential effects of climate change on emerging plant pathogens and their effect on food security. An emerging pathogen is defined as a new pathogen or a previously known pathogen in a new place or host. 

In terms of yield losses, fungi are most important emerging pathogens. Fungal crop diseases have been increasing in severity and scale since the mid-20th century and now pose a serious threat to global food security and ecosystem health.

Devastating impacts of crop pathogens

Staple calorie crops, such as cereals and potatoes, are obviously of key importance to food security. We analysed data from the Food and Agriculture Organization of the United Nations (FAO) to determine which are the most important calorie crops around the world. 

In simple terms – based on the provision of calories per capita per day – rice comes in first place. In other words, rice is the mainstay of more diets across the global population than any other crop. It is followed by wheat, sugarcane, maize, soybean and then potatoes. 

Global yield data indicate that these six crops are also grown in the greatest quantities worldwide. In agricultural settings today, three of these top six – wheat, soybean, and potato – are threatened by emerging fungal pathogens.

For the potato, this may be a familiar story. Today’s threat comes from the same organism that caused the devastating Irish potato famine of 1845-49 (also known as the “Great Famine”), which caused the deaths of a million people in Ireland and pushed another million to emigrate.

Signs of potato blight (Phytophthora infestans). Credit: Danler / Alamy Stock Photo. PENFC7
Signs of potato blight (Phytophthora infestans). Credit: Danler / Alamy Stock Photo.

This is a fungus-like organism called an oomycete. Oomycetes can infect plants, marine life and animals (including humans). The oomycete responsible for Irish potato famine – commonly known as potato or late “blight” – is called Phytophthora infestans. It is appropriately named: from the Greek for plant (phytón) and destruction (phthorá). Infection with Phytophthora causes plant leaves to shrivel and turn brown and the potatoes to rot (it also has a similar effect on tomato plants). 

In 1845, a single strain of this pathogen arrived from Mexico as a newly emerging pathogen in Europe, where potatoes had never encountered it before and were very susceptible. Today, diverse strains are re-emerging worldwide.

Threats to global staple food crops

The main pathogens facing wheat and soybean are, perhaps, less well known than potato blight, but their emergence and the threat they pose is equally dramatic.

Soybean is an incredibly important calorie crop both for food and livestock feed and is threatened by a rust fungus which can travel globally on air currents. On arrival where conditions are suitable, soybean rust may cause 80% yield losses

The increased frequency of severe weather events under climate change may make this pathogen harder to predict and mitigate against – it is already thought to have hitched a ride from Colombia to the US on Hurricane Ivan in 2004. 

Wheat, meanwhile, is threatened by a number of fungi. In Europe, for example, the most important is Septoria tritici blotch (STB), which costs UK growers alone around €240m per year in yield losses. STB is caused by the fungus Zymoseptoria tritici and is thought to spread on wind-blown spores.

STB took the top spot from another fungus – Stagonospora nodorum blotch – which has declined in prevalence in the UK. Stagonospora is thought to benefit – indirectly – from acid rain and, therefore, has become less prominent as anti-pollution legislation in the 1970s saw levels of atmospheric sulphur fall.

Wheat plant showing characteristic ‘blotches’ on leaves caused by STB. Credit: Helen Fones.

This rather surprising correlation between a wheat pathogen and atmospheric pollution demonstrates the sensitivity of crop pathogens to anthropogenic changes in the environment. 

Wheat is, however, more urgently threatened by “wheat blast” – a disease that has emerged as a novel pathogen in Brazil and the US, having jumped from other grass species. Wheat blast – caused by a wheat-specific strain of the fungus Pyricularia oryzae – reached Asia recently, causing up to 50% crop losses in Bangladesh.

In this context, it is gravely concerning that the global population relies so heavily for calories on so few crops. Due to global trade and changes in climatic suitability for crops, global food supply has become more homogeneous and populations more interdependent. 

For example, our study shows that the area of soybean cultivation has increased dramatically since 1980 – and it is extensively grown in monoculture (as a single crop). In contrast, areas of crops like millet and sorghum have decreased. Wheat, meanwhile, has seen a net drop in cultivation area alongside a relocation of that area globally. Global yields have not fallen, indicating that the new wheat growing areas may be more efficient than the old. 

The table below shows the largest losses (left side) and gains (right side) in harvested crop areas across the world between 1980 and 2007.

Greatest gains and losses in crop production area
CountryCropArea (Mha)CountryCropArea (Mha)
ChinaSweet potato-3.27IndiaWheat6.83

The largest changes in harvested crop areas around the world over 1980-2017. In total, 108 crops in 202 countries and territories were analysed using data from the FAOSTAT dataset. Source: Fones et al. (2020)

Such increases in yields are a possible silver lining of climate change for agriculture. But some of my colleagues at the University of Exeter have demonstrated that, as crops move to new areas, they are followed by their pathogens – responding to changes in climate and host availability. The increased disease risk then offsets gains in yield.

Threats to commodity crops

It is also important to bear in mind that food security is not simply about staple crops. Exported commodity crops are the bedrock of many economies. We analysed the FAO data to determine which crops can be described as the world’s most important commodities.

We found that cassava is the top commodity crop in Africa; coffee and bananas in Central and South America; tomatoes in Asia; grapes in Europe; barley in Oceania; and tomatoes and almonds in North America. 

Many of these crops are also under threat from emerging crop pathogens and may be susceptible to others as the climate warms. 

Bananas, for example, are threatened by both “Panama disease” (Fusarium wilt) and “black sigatoka” (Mycosphaerella fijiensis), both of which are emerging fungal diseases. The spread of Panama disease even necessitated the replacement of the globally dominant variety of banana – called “Gros Michel” – with a resistant variety called “Cavendish” in the 1950s.

Banana tree displaying symptoms of black sigatoka. Credit: AePar / Alamy Stock Photo. 2AH1H02
Banana tree displaying symptoms of black sigatoka. Credit: AePar / Alamy Stock Photo.

However, a new strain of Panama disease (known as “TR4”) subsequently emerged in the 1960s and gradually spread worldwide. As the map below illustrates, this spread accelerated recently and TR4 entered the major banana growing country, Colombia, in 2019. This has triggered media reports of impending “bananageddon” and a state of emergency in that country.

Spread of TR4 Fusarium wilt throughout global banana-exporting regions. After TR4 arose in Taiwan in the 1960s, it rapidly spread throughout the world’s Cavendish banana growing regions. First reports in a given country are shown as stars on the map, colour coded for decade or year. Source: Fones et al. (2020)

Modelling future disease risk

Predicting the behaviour of crop pathogens under climate change is not simple. Disease depends on what is known as the “disease triangle”, in which the pathogen is affected by its host and both are affected by environmental factors such as nutrient availability and climate.

The “disease triangle” for plants. Disease relies on the pathogen, host plant and wider environmental factors and only develops where all three are conducive at the same time and in the same place. Credit: Helen Fones

The simplest models seek to correlate observed disease to weather data. Such models can be effective in predicting disease risk where simple weather-related factors control disease. 

For example, STB disease of wheat is known to be limited by hot, dry weather, partly because dispersal of the fungal spores relies upon rain splash from leaf to leaf. Predicted increases in the frequency and duration of such spells could be used to predict reduced STB risk. 

In more complex situations, however, these correlative models tend to break down. This leads to a need for “mechanistic models” that take into account the complicated biological workings of the host and pathogen. 

The improved availability of high-resolution climate reanalysis data – which combines observed data and model output – also allows us to derive information about factors such as the temperature of canopy temperature and leaf wetness duration. This data makes the production of complex models a viable option. 

My colleague, Prof Dan Bebber, has produced such models for several fungal diseases. In coffee leaf rust, for example, the model showed that climate change was likely not responsible for a recent outbreak in Colombia. However, a black sigatoka disease model demonstrates that climate change has increased leaf wetness and made temperatures more favourable for this fungus in banana growing regions, increasing the disease risk by 44%.

However, while models can inform us about the importance of climate variables and allow us to test hypotheses about the causes of observed changes in disease prevalence, accurate predictive models still do not exist for many diseases. 

This is because climate interacts with all other aspects of the disease triangle. It affects not only where and when a crop is grown, but determines whether that plant is stressed or healthy, which in turn affects disease resistance. At the same time, it controls pathogen survival and spread. Meanwhile, socioeconomic effects may be felt in agriculture, which may in turn affect plant health and disease outcomes. 

Even more difficult to predict are complex interactions between climate, human behaviour, and non-climate environmental factors such as air pollution. Just as sulphur gases affected wheat pathogens in the 1970s, atmospheric concentrations of other gases – such as ozone and nitrous oxides – also alter plant defenses and pathogen performance

As we have seen, pathogens tend to migrate to follow suitable climates, as long as their hosts are present. This means that as humans respond to climate change with altered agricultural practice, crop diseases are likely to keep pace.

Fones, H. N. et al. (2020) Threats to global food security from emerging fungal and oomycete crop pathogens, Nature Food, doi:10.1038/s43016-020-0075-0

Update: The article was updated on 13/06/2020 to correct the global population to “almost eight billion” instead of “nine billion”. Sharelines from this story

  • Guest post: How climate change could accelerate the threat of crop diseases
  • Guest post: Climate change, food security, and emerging crop pathogens

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