Britain’s ash trees could be wiped out by an Asian beetle just as they begin to recover from the devastating ash dieback fungus, scientists have warned.
In the latest State of the World’s Plants report, exerts at the Royal Botanical Gardens at Kew said that the emerald ash borer beetle was on the march to Europe and could be even more deadly than ash dieback.
Chalara ash dieback, which is expected to kill 50 per cent of the country’s 120 million ash trees, was first identified in the UK in 2012 but hope emerged last year when scientists discovered a tree in Ashwellthorpe Wood, in Norfolk, which was resistant to the disease.
But now experts fear the emerald ash borer could soon arrive in Britain and wreak devastation in a similar way to US cities, where tens of millions of ash trees across 25 states have withered and died at a cost to the economy of $10 billion. It has already been found west of Moscow.
“There is a real chance that the emerald ash borer could come to the UK. It’s currently devastating ash populations in America and it’s currently found around Moscow in Russia and research shows it is spreading towards Europe, so over the next few years we could see it enter Europe and spread through and find ash trees already weakened by ash dieback.
“And it’s actually far more damaging than ash dieback.
“It is has killed huge numbers of trees in America and they have a lot of avenues of ash trees in towns and some of them have been completely wiped out.”
The emerald ash borer beetle, Agrilus planipennis, is native to north-east China, the Korean peninsula, Japan, Taiwan, Mongolia and the Russian Far East.
It lays its egg on the bark of the trees and then the larvae burrow into the trees, eating into the green tissue beneath which supplies nutrients and water, until the tree dies. Trees which had survived hundreds of years can be killed in just a couple of years once the beetle has moved in.
Although the adult beetles only live for a matter of weeks, an individual female can travel six miles (10km) and lay in excess of 200 eggs during their short lives, so populations can swell and spread quickly.
Kew Gardens is currently working with the US Forest Service test how susceptible British trees are compared to Chinese trees, which have a natural resistance to the pest. Worryingly they found that European ash are unlikely to be able to fight off the beetle.
Experts believe it has been able to travel by hitching a ride on shipping crates, which have not been properly treated with pesticides. In America, the first beetles arrived on timber pallets which were used to ship products from China to Detroit.
“It’s an unintended consequence of globalisation,” added Dr Buggs.”
“Every palate if you’re moving stuff internationally should be treated so it’s not carrying beetles or pathogens, but sometimes that doesn’t happen. In some countries there is faking of the symbol that is supposed to be on a palate to show it has been treated, so wood packaging is one of the means by which pests and pathogens are spreading around the world.”
Experts at Kew said an outbreak could have a much wider impact than simply the death of trees.
“It’s also about the loss of ecosytems that go with the trees,” added Professor Kathy Willis, director of Science at Kew, and the editor of the new report.
Previous studies have shown that the loss of Britain’s ash trees could wipe out 45 native species and endanger the habitats of nearly 1,000 others.
“Across the United States whole avenues of ash are disappearing,” added Prof Willis. “The sad thing is, it’s not just that you’ve lost your street furniture, but as a city loses the trees you get an increase in respiratory problems and an increase in mental health problems.”
The report also revealed that 1,730 new plant species were discovered in 2016, including 336 new orchids, 29 new begonias, 11 never-before-seen aspidistras and a new parsnip.