Wheat provides 19% of calories and 21% of protein consumed by humans worldwide. But a fungal disease called fusarium head blight (FHB), which can infect wheat crops and contaminate the grain with toxins, is on the rise.
These so-called mycotoxins – which include deoxynivalenol, commonly known as “vomitoxin” – pose a threat to human and animal health and can cause vomiting, intestinal damage, weakened immune systems, hormonal disruption and cancer.
To protect consumers, the European Commission has set legal limits on vomitoxin levels in wheat produced for food. Cereals deemed too contaminated for human consumption are often downgraded to animal feed. But downgrading comes at a cost to farmers and the economy, as animal feed has a lower monetary value than food.
Governments and food companies routinely monitor mycotoxin levels in the food and animal supply chains. Yet the extent of FHB mycotoxin contamination in European wheat supplies is understudied and its economic impact has not been quantified before.
Together with colleagues from the Universities of Bath and Exeter, we analyzed the largest mycotoxin datasets available and found that FHB mycotoxins are prevalent in wheat produced for food and feed across Europe. . We have also found that the threat of mycotoxins – especially in southern Europe – is increasing over time.
Contaminated European Wheat
Vomitoxin was present in all European countries studied, and overall it was found in half of all food wheat samples. In the UK, vomitoxin was found in 70% of food wheat produced between 2010 and 2019.
Almost all (95%) of the vomitoxin contamination recorded in European wheat was within legal limits. This confirms that current legislation and monitoring of FHB mycotoxin levels in food effectively protect European consumers against acute poisoning.
Yet the widespread presence of vomitoxin in our food is concerning. It is not yet known to what extent constant, low-level dietary exposure to mycotoxins can affect human health in the long term. This is compounded by the fact that a quarter of the vomitoxin-contaminated wheat also contained other FHB mycotoxins, raising concerns about synergy, where the toxins interact with each other and cause more damage than the sum of the individual toxins acting alone.
Economic cost of fungal toxins
We have also estimated the cost of vomitoxin to the European economy.
Vomitoxin has been recorded at levels above legal limits in 5% of wheat produced for food in Europe. Between 2010 and 2019, this was equivalent to 75 million tonnes of wheat. If all this affected wheat were diverted to animal feed, we calculated that the loss in value for wheat farmers would be €3 billion (£2.6 billion) over the period studied.
However, the total economic cost of Fusarium wilt in Europe is likely to be much higher. Our calculation does not include the reduction in wheat yields resulting from disease, contamination with other harmful but less regularly tested mycotoxins, or the costs of applying fungicides to prevent the growth of the fungal pathogen.
Fusarium wilt is a disease that fluctuates every year. But we found that mycotoxin levels increased in lower latitude countries between 2010 and 2019, which is particularly the case in the Mediterranean. The vomitoxin concentrations recorded during the 2018 and 2019 epidemic years, for example, were the highest over the period studied.
Our study did not investigate the causes of this increase. But it’s likely that changes in farming practices, climate change and declining fungicide efficacy are all contributing factors.
Minimum tillage, where land is cultivated using methods other than tillage to reduce soil disturbance, is an increasingly popular farming method. The method benefits soil health but leaves crop debris behind and allows the FHB fungus to survive the winter. Maize, a crop very susceptible to Fusarium wilt, is also widely grown throughout Europe. Combined, these agricultural practices increase the pathogen load of Fusarium wilt in the environment.
Climate change may also promote the spread of Fusarium wilt disease. Warmer, wetter weather coinciding with the wheat flowering period provides ideal conditions for the FHB fungus to infect and produce mycotoxins.
Resistance to azoles, a commonly used fungicide, has been increasingly reported in recent years. Naturally and through repeated exposure, fusarium fungal species are more resistant to these fungicides than other fungal pathogens.
FHB contamination is widespread throughout Europe, resulting in substantial cost. Understanding Fusarium wilt disease and its mycotoxins is therefore important. But surveillance of FHB outbreaks needs to be improved to allow researchers to predict which environments are most at risk for mycotoxin-causing fungal diseases in the future.
Methods of disease containment also need to be further developed. These include new fungicides or future crop protection strategies that inhibit the development of mycotoxins. Climate change is leading to more crop disease outbreaks and our need for a secure food supply is increasing, so the issue of mycotoxins will only grow in importance.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Neil Brown works for the University of Bath. He receives funding from the BBSRC Future Leader Fellowship BB/N011686/1, an internal scholarship from the University of Bath and a scholarship from the Royal Society RGS\R2\202128.
Louise Johns is a PhD student at the University of Bath. Louise Johns was funded by an URSA Fellowship from the University of Bath and a British Society for Plant Pathology Covid-19 Doctoral Support Fellowship.