Daily Times

As well as olive trees, it can also infect cherry, almond and plum trees but is mainly associated with olives after a strain was discovered in 2013 in Puglia, Italy.

Once the infection enters the tree, it limits its ability to move water causing it to eventually die.

Italy in 2013, the infection has seen roughly a 60 per cent decline in crop yields.

Dr Maria Saponari, from the CNR Institute for Sustainable Plant Protection in Italy, told the BBC: ‘The damage to the olives also causes a depreciation of the value of the land, and to the touristic attractiveness of this region.

‘It’s had a severe impact on the local economy and jobs connected with agriculture.’

Tens of thousands of olive trees are imported into the UK every year.

The figures of imported lavender and rosemary plants are even higher.

In a letter, the Department for the Environment, Food and Rural Affairs (Defra) said that “there remains an unacceptable level of pest risk and we are introducing national measures in the absence of EU requirements”.

“They’re quite stringent requirements and they will very much impact the trade flows of things like olive and lavender where huge quantities are moved around in the horticultural trade,” said Dr Gerard Clover, from the John Innes Centre in Norwich.

If measures are taken to protect olive groves, the overall economic impact could be lowered to around 1.6 billion euros (£1.3 billion) in Italy, €5b (£4.4bn) in Spain and €0.6bn (£0.5bn) in Greece.

But this increase in costs could also see a rise in the price of olive oil, according to the study.

“Most olives are used as an input for processing into olive oil,” the researchers write. ”In turn, the simulated price increase would result in higher costs of production for oil processors. This could affect the consumer price for olive oil.”