Many of the world's most important crop-producing countries will be fully saturated with pests by the middle of the century if current trends continue, according to a new study led by the University of Exeter.

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More than one-in-ten pest types can already be found in around half the countries that grow their host crops, researchers said. If this spread advances at its current rate, scientists fear that a significant proportion of global crop-producing countries will be overwhelmed by pests within the next 30 years.

The international research project looked at the factors behind pests' spread, using global databases to investigate the number of countries reached by pests, the number of pests in each country and the possible influences for their spread. Scientists investigated the distribution of 1,901 crop pests and pathogens and used records dating back to 1822 to monitor their distribution.

Experts have suggested that the range of crop pests and diseases could spread as climate change worsens. The IPCC report on the impacts of climate change, published in March, warned that human-driven changes are already affecting agriculture in almost every global region. The Exeter scientists said their findings support these earlier warnings.

Dr Dan Bebber of Biosciences at the University of Exeter commented on Thursday, "If crop pests continue to spread at current rates, many of the world's biggest crop producing nations will be inundated by the middle of the Century, posing a grave threat to global food security."

Disease threats underreported in EU

The study authors looked at which pests are likely to be the most invasive in coming years. Around the world, fungi are leading the invasion into new areas; fungi are the most widely dispersed crop pest group, despite having the narrowest range of hosts.

Worldwide, potential new threats include: three species of tropical root knot nematode whose larvae infect the roots of thousands of different plant species; Blumeria graminis, a fungus that causes powdery mildew on wheat and other cereals; and the Citrus tristeza virus (given its name meaning 'sadness' in Portuguese and Spanish by farmers in the 1930s) which had reached 105 of 145 countries growing citrus fruits by 2000.

Speaking to Farming Online on Thursday, Professor Sarah Gurr, co-author of the research, said, the threat from new pests in the UK is "Not significantly different from [other] Northern EU countries… What is significant is that most of the countries are underreporting their current pathogen / pest 'load'".

Elaborating on the potential threats that UK farmers could face, Prof Gurr added, "The fungi are the most invasive. We may well see more powdery mildews and more 'tropical' fungal species in Northern EU states. Certain rust and leaf spot fungi [may] pose a problem on cereals. We may see more new variants of old diseases such as late blight of potato. We may also see more nematode diseases to add to our current problems with cyst nematodes."

Professor Gurr said that, though "New, virulent variants of pests are constantly evolving" and the findings published today are concerning, "There is hope if robust plant protection strategies and biosecurity measures are implemented, particularly in the developing world where knowledge is scant."

"Whether such precautions can slow or stop this process remains to be seen," Prof Gurr added.

Even so, researchers have hope that by mapping and understanding the spread of pests and pathogens, people can respond to the risks. Dr Timothy Holmes of CABI's Plantwise knowledge bank, commented, "By unlocking the potential to understand the distribution of crop pests and diseases, we're moving one step closer to protecting our ability to feed a growing global population. The hope is to turn data into positive action."

To reduce the potential impact of new threats at farm level, Professor Gurr recommended "More sustainable farming practices, less reliance on a few inbred disease resistant genes and single target site antifungals (which hasten emergence of resistance in pathogen population)."

Gurr also welcomed recent moves at policy level, such as the "Government Agritech strategy and EU Horizon 2020 [which] herald a change in attitude to agriculture." nevertheless, the biosceinces professor added that "More early detection and biosecurity, more training" are necessary to minimise the threat, alongside "More public and political awareness."

Dr Bebber suggested that "Avoiding unnecessary imports of live plants and fresh vegetables, which can be grown in the UK" could also lessen the risk of spread, though the study co-author added that the problems caused by pests and disease will be felt worldwide, warning that "Food prices in the UK and Europe are strongly affected by production in other parts of the world, as we live in a globalised society."