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Plant diseases are increasingly destroying EU trees and crops

While farmers and conservationists struggle to contain previously introduced pathogens, new outbreaks are being detected. According to scientists, the problem will only get worse as temperatures rise.

Infectious diseases don’t just threaten the health of humans and animals.

Plants are also susceptible to new pathogens, and scientists are concerned that a growing number of species could be at risk as temperatures rise and the climate, as a result, carries on changing at an unprecedented rate.

Since 2013, over 20 million olive trees in Italy – a third of its 60 million – have been ravaged by a deadly and hard-to-detect type of bacterium called Xylella Fastidiosa, which could see many more plant species, across several countries, succumb to the same fate.

This is because the insect (called meadow spittlebugs) responsible for inadvertently transmitting the bacterium can suck the sap from a vast range (some 1,300 and counting) of different plant species, including trees that are commonly grown in the British countryside and the crops that feed us.

The list is long and growing, already comprising 690 species across 88 plant families.

Throughout Europe, data shows that while farmers and conservationists struggle to contain the previously introduced Xylella Fastidiosa pathogen, new disease outbreaks are being detected.

In fact, these outbreaks have continued to progress unabated at an average level of 70 a year between 2015 and 2020, despite regulations put in place in 2016 to curb their spread.

Already, plant diseases cost the global economy over $220bn every year, and invasive insects at least $70bn, according to the UN’s Food and Agriculture Organisation.

The resilience of these diseases is thought to be in direct correlation with our increasingly warming planet, which provides the perfect conditions for pests to generate more quickly and migrate faster, and outbreaks to thrive and run rampant.

In the absence of hostile environments to prevent pathogens from adapting and developing resistance to common methods of controlling them, the impact of this is expected to worsen.

‘With climate change comes drought, which makes plants stressed, and when they’re stressed, they become more susceptible to pathogens in the environment,’ forest pathologist, Tod Ramsfield, told CBC.

‘The number of diseases – and the extent of the infections – is going up. So, under hotter conditions, and in some areas, more humid or arid, those infections become more prevalent and extensive.’

As he explains, insects aren’t solely to blame for the upticks in outbreaks.

Human movement is also fuelling the spread of pathogens between continents, whether through global trade or tourism.

Confirming this is evidence that Xylella Fastidiosa came from Latin America and, most likely, hitched a ride on ornamental coffee plants passing through the Netherlands.

About 30bn rooted and unrooted plants, cuttings, bulbs and tissues came from third countries into Europe between 2005 and 2014, mainly through Dutch ports.

‘With the current system in Europe, we continuously introduce new organisms,’ plant epidemiologist, Pierfederico La Notte, told the Guardian.

‘In the context of climate change, it will be more and more difficult to manage them.’