Climate change is helping pests and diseases that attack crops to spread around the world, a study suggests.

Researchers from the universities of Exeter and Oxford have found crop pests are moving at an average of 3km (two miles) a year. The team looked at more than 600 pests, including the Colorado potato beetle.

The team said they were heading towards the north and south poles, and were establishing in areas that were once to cold for them to live in.

The research is published in the journal Nature Climate Change.

Currently, it is estimated that between 10% and 16% of the world's crops are lost to disease outbreaks. The researchers warn that rising global temperatures could make the problem worse.

Dr Dan Bebber, the lead author of the study from the University of Exeter, said: "Global food security is one of the major challenges we are going to face over the next few decades.

"We really don't want to be losing any more of our crops than is absolutely necessary to pests and pathogens."

Trade transport

To investigate the problem, the researchers looked at the records of 612 crop pests and pathogens from around the world that had been collected over the past 50 years.

These included fungi, such as wheat rust, which is devastating harvests in Africa, the Middle East and Asia; insects like the mountain pine beetle that is destroying trees in the US; as well as bacteria, viruses and microscopic nematode worms.

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