Beetles enlisted to save the spruce – from beetles

Spruce is one of our nation’s most important commercial tree species, and it’s under attack. The great spruce bark beetle was, scientists believe, brought to the UK among imported timber around 30 years ago, and since then has become an established pest in Western England and in Wales.

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Beetles enlisted to save the spruce – from beetles

It attacks, and breeds in, all species of spruce grown in Britain. The female burrows into the tree, and lays its eggs under the bark. The larvae feed on the wood under the bark, and if left unchecked, will eventually kill the tree, and spread to its neighbours. An infested tree appears to be bleeding resin. Browning foliage over the crown is another symptom.

Because of its potential to cause damage not just to trees, but also the rural economy, much research has focused on how best to tackle the beetle.

And the best answer is, it appears, another beetle.

John Wilding, Head of Forestry and Environment for Clinton Devon Estates, said: “Wood is the ultimate renewable resource and timber from well managed forests can be better than carbon neutral. Each year we harvest around 20,000 tonnes of timber, certified by the Forest Stewardship Council, for use locally and beyond for building material, fencing, and fuel.

“So it’s vitally important that we are able to tackle the range of natural threats to our forests, including the great spruce bark beetle, which, if left uncontrolled, can lead to forest death.”

Working in conjunction with Forest Research, part of the Forestry Commission, John decided to enlist nature to control the pest. He said: “We’ve recorded the great spruce bark beetle in forests near Hawkerland for three or four years, and the Forestry Commission recommend a completely natural prey to help tackle it. It’s a tiny beetle known as Rhizophagus grandis which has only one source of food – the great spruce bark beetle. R Grandis, as it’s known, is specially bred in the lab to be introduced to infested trees and fight the problem head-on.

“The female R Grandis eats only the eggs of the great spruce bark, and her larvae will similarly attack the unwanted invader, so the use of this one species of beetle to attack another much more damaging one is a very neat, natural solution. R Grandis just won’t eat anything else, and certainly doesn’t cause any damage to the spruce tree. If it has no prey it will just die out but, that said, it is very good at tracking down its food!”

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