Country: Invasion of the bark beetles

Helen Lewis
Saturday 14 September 1996 00:02
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The eight-toothed spruce bark beetle could pose a threat to British forestry comparable to the Dutch elm disease disaster of the 1970s. Already, huge acres of continental forests have been devastated and there are now fears the beetle is poised to commit mayhem in Britain.

Between 1945 and 1949, Germany lost 30 million cubic metres of timber to bark beetles - five times Britain's annual timber harvest. In 1982, the beetle took Sweden. In that year alone, two million hectares of timber were destroyed.

Now this lethal pest is being found in considerable numbers caught in insect traps set by the Forestry Commission at British ports: "During the last couple of years, numbers of this beetle arriving in Britain have risen to an alarmingly high level," says Roddy Burgess, head of plant health for the Forestry Commission.

It is an international legal requirement that all timber imported into a beetle-free country must be devoid of bark. The concern is with sub- standard pallet imports from the Baltic States arriving at without being debarked. These are often infested with "the most aggressive bark beetle known in Europe", according to the Timber Packaging and Pallet Confederation.

The beetle can only survive in bark - not in finished sawn timber. It could enter Britain lurking in any type of imported timber, from wood shavings used for packing material to wooden crates or even sawn lengths if they still have some vestige of bark on them. And the Forestry Commission doesn't hold out much hope for this country remaining beetle-free for much longer: "It is inevitable that the eight-toothed spruce bark beetle will get a foothold in Britain one day, all we can do is try to put that day off," Burgess says.

"The beetle kills trees by boring its way into the bark and setting up a breeding site. This boring action severs the food supply to the tree's root system and - if enough beetles are present - can starve it to death in a matter of a few weeks. However, they can only survive in large numbers. "One insect getting into this country would not survive alone, around 200 are required to form a colony and start killing trees," adds Burgess.

The acreage in danger is phenomenal. Spruce is the most predominant and commercially important species in Britain: 50 per cent of softwood forests are spruce - 800,000 hectares. On the continent, the beetle has also been found living in pine, larch and douglas fir.

Already its relative is chomping in Britain. The great spruce bark beetle is nowhere near as devastating as its eight-tooth cousin: "We may have the great spruce bark beetle in Britain forever, but we have contained it so far to Wales and bordering counties," Burgess explains.

The spread of this species of bark beetle has been limited because rigorous laws are in place, preventing timber with bark being moved from infested regions to elsewhere in the country. Any trees felled within the contaminated area must only be sawn at an approved mill where the bark can be safely destroyed.

It is thought this beetle started arriving in 1973 but remained undetected until 1982. By the mid Eighties an insect predator which feeds exclusively on the beetle larva was discovered and released into the infected areas. Tree destruction has been minimal since then.

However, no one has found a way of restraining the eight-toothed beetle. "Once this beetle takes hold it is here for good," warns Burgess. "There is no method of control, the only solution is to remove and destroy infected trees to reduce the numbers of newly emerging beetle larva. Speed will be essential as it can breed three times a year."

Scientists are seeking ways to control the insect should it become established in Britain and timber importation regulations have been tightened. All ships carrying any cargo of soft wood must notify the Forestry Commission three days before docking at a British port. If the timber is arriving from the Baltic Stales, it is inspected before unloading and, if found to be infested with the beetle, sent straight back.

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