Farm Ireland

Friday 23 February 2018

Asian beetle could wipe out ash trees...and is heading our way

Emerald ash borer. Photo: Royal Botanical Gardens
Emerald ash borer. Photo: Royal Botanical Gardens

Sarah Knapton

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 or Ash Dieback disease is a disease of ash trees caused by the fungus Hymenoscyphus fraxineus and it has spread rapidly across Europe in recent years.

And the latest figures from the Department of Agriculture show that year on year that there is a continuing rise in the number and geographic distribution of confirmed findings nationally and is present in every county.

A young Common Ash Tree with wilting leaves shows the symptoms of dieback
A young Common Ash Tree with wilting leaves shows the symptoms of dieback

But now experts fear the emerald ash borer could soon arrive in Northern Europe 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.

Dr Richard Buggs, head of plant health at Kew, said the beetle could be the ‘final nail in the coffin’ for Britain’s ash trees.

“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 that ash dieback.

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“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 pallet 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 pallet to show it has been treated, so wood packaging is one of the means by which pests and pathogens are spreading around the world.”