Arable Matters: 'Fungus the Bogeyman' raises cause for concern

At the same time, though, it can’t be denied that with your nose pushed tight up against the one small window through which you view the world, it can sometimes be a bit difficult to take in the wider picture.

So, as our own obsession with getting crops into the ground takes that step forward towards one which is concerned more with keeping it growing and healthy through to harvest, it was interesting to chance upon a call from a leading scientist for politicians and policymakers to waken up to the scale of the threat posed to food security by crop diseases.

Now, it was only last year that the World Health Organisation (WHO) published its first ever assessment of the threat posed by fungal diseases to human health – with the aim of systematically prioritising surveillance, research and development and public health interventions to counter what was widely viewed to be a growing threat.

However, that piece of work failed to factor in what might be an even bigger, although perhaps less direct, hazard to human health – the fact that fungal diseases probably constitute the most serious threat to crop production in many parts of the world, including our own.

A comment piece in a widely respected scientific journal flagged up the fact that this area is currently receiving far less attention than it deserves, because while the dangers posed directly to human health by fungal diseases might be significant, the indirect threat posed to food security is arguably far greater.

READ MORE: Arable Matters: Too reliant on technology to cope without it?

For, let’s face it, there are literally hundreds of fungal diseases which seem to be set to attack virtually every single major food crop which is grown around the globe – and climate change seems set to make the threat even greater.

Despite the best attempts of farmers and agronomists to control these diseases – by the spraying of crop chemicals and increasingly by the adoption of additional methods like integrated crop management – the paper highlighted the fact that somewhere between 10% and 25% of all crop production is currently lost as a result of fungal infections each year. That's a loss which would be enough to feed up to 4bn hungry mouths around the world.

The article also pointed out that fungal disease took the top six places in a list of the major disease threats to food crops around the world. It estimated that septoria tritici alone often caused crop losses in the region of 5-50% in temperate regions, whilst wheat stem rust, which is more prevalent in tropical areas, saw losses vary between 10 and 70% of any expected harvest.

At the root of the problem is the incredible capacity of fungi to produce millions upon millions of spores – which can travel for many miles on air currents and which can often live for long periods on crop trash and in soils.

On top of this, there is a huge degree of genetic variation and plasticity which, as we all know to our cost, allows new strains of fungi to evolve at a speed which often seems to significantly outstrip our ability to either breed resistant varieties or to come up with new crop protection products which would allow us to control the threat.

Of course, there’s no getting away from the fact that growing large areas of crops which are largely genetically identical provides ideal feeding and breeding grounds for such a prolific and fast-evolving group of organisms.

As has probably been highlighted by the loss of chlorothalonil in recent years, we’ve been pushed towards an over-reliance on anti-fungal treatments which rely all too heavily on compounds which target a single metabolic process in the infecting fungi.

This is because the vast majority of the modern fungicides which we use have single-site modes of action which act on specific biochemical pathways in the target fungal pathogen. And the consequence of the repeated use of products with the same mode of action is to select for isolates of the fungal population which have a reduced sensitivity to the fungicide, an outcome which inevitably leads to a loss of efficacy and the ability to control outbreaks.

Taken together, the azoles, strobilurines and succinate dehydrogenase inhibitors (SDIs) – all of which are single target site specific products – account for more than three-quarters of the global fungicide market, meaning we’re effectively pinning all our hopes on a small range of products which are wide open to the sudden emergence of a dominant strain which is resistant to the few remaining weapons in our armoury.

So, if nothing else, this threat should be enough to ensure that we all stick to the recommendations on the use of products which have been issued by the UK’s Fungicide Resistance Group (FRAG) on a regular basis over recent years.

But while we’ve all had drummed into us the approach which we should be taking to make sure we can eke out the effectiveness of these chemicals for as long as possible, a wider strategy is required in the long term. That will involve a high degree of input and collaboration between growers, plant breeders, plant disease biologists, governments and policy makers and even philanthropic funders, like Bill Gates and others, who have declared an interest in helping to feed the world.

That's because research in this area has been lagging a bit and stands well below what can be pumped in by governments and other bodies where a major risk is seen. For instance, between 2020 and 2023, the UK’s research council spent over £600m on Covid 19 research, with almost 225,000 research papers being published on the issue. Yet over the same timescale less than £30m was spent on fungal crop research and only 4000 papers were published.

So while the children’s picturebook 'Fungus the Bogeyman' might have been used to scare the kids in their early years, it might be worth reprising the effect to raise the political profile of what is clearly an under-appreciated threat to the human race.