Now ash trees under threat from beetles

Emerald ash borer, 'Agrilus planipennis. 'David Cappaert
Emerald ash borer, 'Agrilus planipennis. 'David Cappaert
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An invasive beetle that has destroyed tens of millions of ash trees in the US could pose a lethal threat to struggling native trees in the UK.

The emerald ash borer which arrived in Moscow seven years ago presents a serious threat to ash trees in Europe, researchers have warned.

At a conference at Hull University co-organiser Dr Nigel Straw said the pest was at the top of the list of threats to native trees as “we know it kills ashes, we know it is spreading and it will get here eventually.”

The iridescent green beetles, which probably travelled to Russia in packaging from Asia, has now spread some 150 miles from the capital, possibly by “hitch-hiking” on vehicles.

So far they are thought to have killed 1m trees.

There are concerns that the pest will threaten trees in this country, already weakened by ash dieback disease.

The latest figures show the deadly wind-borne fungus - first identified in 2012 - has been found in just under 1,000 locations in the UK, with new cases now averaging 20 a month.

The disease has been found in at least 15 established woodlands in Yorkshire, including along the East Coast, south from Bridlington, between Hull and Beverley and in the Market Weighton area. It has also been confirmed in the Stamford Bridge area as well as Nidderdale, Keighley and Malton.

Native to China, the beetle larvae tunnel under the bark, girdling the tree and cutting off the flow of water and nutrients. Dr Straw, who has seen the damage caused by the pest first-hand in Russia, said it was heading west towards Belarus. In continental Europe it is estimated 95 per cent of ashes have already been lost through ash dieback.

He said: “The beetle certainly does more damage to trees that are stressed if they already suffer from ash dieback. They are two agents almost synergistically working against trees. The two big questions are whether the ash may show resistance or whether our climate being cooler and wetter may not favour the beetle.”

Dr Straw, from Forest Research, said there didn’t tend to be simple solutions to plant diseases and once established we “usually we have to learn to live with it”. However people could help by keeping an eye on the health of local trees, as picking up pests early was vital. He cited how early detection helped snuff out an infestation of Asian longhorn beetles in Kent.

Officials started carrying out surveys after a woman found a beetle in her garden, next to a site which stored slate from China. In 2012 they found larvae of the beetle, which tunnel through the stems and branches, and felled over 2,000 trees in a bid to stop its spread. “It was caught early when the outbreak was quite small and seems to have been really quite successful,” said Dr Straw.

Delegates expressed concerns about the increasing number of pests and diseases arriving on UK shores as a result of international trade. Sarah Redstone, plant health and quarantine officer at Kew Gardens, said ideally people would buy plants grown in the UK: “Global travel and trade and the Internet linked to the changing climate means that this is a particularly difficult time. If we want to ensure future security and make sure plants have a long and healthy life we need to look at what we do and how we do it, including people making choices about where they buy plants for their gardens.”