Home > Britain, disease and pestilence > Red alert in Britain’s forests as Black death sweeps in

Red alert in Britain’s forests as Black death sweeps in

February 4, 2011

Millions of larches have had to be felled to prevent the spread of a lethal virus from Asia. Christopher Middleton reports from the bleak and bare hillsides of South Wales.

Kill and cure: a disaeased larch forest being cleared at Crymant, near Neath. 

Kill and cure: a diseased larch forest being cleared at Crymant, near Neath. Photo: JAY WILLIAMS
By Christopher Middleton

Just before Christmas, you could stand at the top of Crynant Forest in South Wales and not have a clue that there was a village in the valley below. Today, the view down to the little white houses is uninterrupted. Where in mid-December there were thousands of larch trees, now there is a mass of stumps and branches.

It looks like a photograph from a First World War battlefield. A featureless no-man’s-land, interrupted by the occasional blasted tree trunk, pointing at an unnatural angle.

And that’s just the start of it. Turn your gaze in any direction, and there is a scene of devastation. Bare hillsides as far as the eye can see; slopes that look as if they’re covered in bracken are in fact coated with fallen trees.

Meanwhile, piles of logs as tall as barns are stacked up neatly by the roadside, like casualties awaiting collection from clearing stations.

The force that swept through here was not a hurricane, but an army of tree-felling engines sent in by the Forestry Commission. Already they’ve cleared 380 acres, but there’s more to be done. Much more.

And they’re in a race against time. Across the country, some 1.4 million larches have been cut down in the past 15 months, and another 1.2 million must go in the next three. Otherwise the problem is only going to get worse.

“Problem?” asks a bemused, predominantly urban Britain. What problem? The answer is a plague of potentially biblical proportions. Remember Dutch Elm Disease, which caused

28 million elms to perish in the Seventies? Well, meet its aggressive younger brother, Phytophthora ramorum, or PR, a fungus-like pathogen thought to have begun in Asia and to have spread to these shores via Europe.

The first sign of PR is when a tree’s foliage starts to wilt or blacken. But by then, it’s too late. Another indication is when the inner bark turns brown instead of green, and a black fluid starts to flow through ugly external lesions. Death usually follows.

Cutting down and removal is the only treatment. Failure to do so will ensure the spread of the disease not just to other trees (beech, sweet chestnut and horse chestnut are known to be susceptible), but to a range of plants, including rhododendron, viburnum, pieris, lilac and camellia (the pathogen devours their leaves and shoots).

Phytophthora ramorum’s first known appearance in this country was nine years ago, on a viburnum plant in an East Sussex garden centre. The pathogen then “leapt” species, and was discovered on rhododendrons. Here, it found the perfect launch pad for a full-scale assault: rhododendrons provided the ideal conditions for the spores to reproduce, or “sporulate”, and then head off further afield, via mist, air, streams, rivers and even rainwater splashes.

Until 2009, forestry officials were on distinctly low alert; only 100 infected trees had been found, usually next to diseased rhododendrons. Then, in 2009, all of a sudden, spores were reported on larches across south-west England, followed the next year by larches in Wales, Northern Ireland and the Irish Republic. Not only that, but the spores were reproducing five times faster than on rhododendrons.

Now on full alert, forestry scientists launched an emergency testing programmer, to determine how far PR had spread. The result is a map of Britain in which red spots denoting PR outbreaks are concentrated like a measles rash throughout Devon and Cornwall, on one side of the Bristol Channel, and the width of South Wales on the other. And while most cases are confined to those areas, outbreaks have been fund as far afield as Shepton Mallet and Scotland. And it’s not just Forestry Commission sites that have been hit, large numbers of privately owned and National Trust estates are victims, too.

Phytophthora ramorum only seems to attack the Japanese larch (Larix kaempferi), not the European (Larix decidua) or hybrid larch (Larix x eurolepis). “The pathogen thrives and spreads best in a moist, mild climate, and climate modelling suggests the southern and western seaboards of Britain are more likely to be affected than the drier eastern regions,” says the Forestry Commission.

Which is why the hills of Cynant, near Neath, are today alive not with the sounds of bleating sheep, but of industrial tree extermination.

The machines carrying out the work are known as “harvesters” and go about their work with brutal efficiency. Like orange Tyrannosaurus rexes, they clamp their ferocious jaws on the base of the trunk with relish. A terrible judder goes through the tree, like an animal into which a predator has just sunk its teeth.

Within seconds, an internal saw has cleaved its way clean through the trunk, upon which the entire tree crashes to the ground. Not relaxing its grip for a second, the machine wrestles the fallen trunk into position and sucks it back through its metal proboscis, first ripping off any protruding branches (called “snedding”) and then slicing up the denuded trunk into neat sections, 6ft 2in in length.

In less than a minute, a 60-year-old larch is converted from towering king of the forest to horizontal, pre-diced lumber.

“It’s a very sad sight indeed,” says Cerith Morgan, a local harvester operator. “Yes, it means more work now for me and my family [there are five Morgans working in this one patch of the forest]. But it means there won’t be any work for us in 10 years’ time, when we would, in normal circumstances, have been coming to thin out these trees.

“You have to take the long-term view, don’t you?”

And the future does not look good for the larch, which won’t be planted in these parts for at least another five years.

“That’s how long the pathogens stay in the soil,” says Lee Dawson, the Forestry Commission man who’s coordinating the fight at against PR in South Wales. “We’re going to have to think very carefully about what we decide to plant instead. About the only positive we can take from the situation is that the timber itself, if properly processed, poses no risk. So at least we can sell what we fell.”

This removes the spectre of Forestry Commission officials raiding homes on suspicion that people might be harboring a fence made with infected wood (larch is used in everything from patio decking to garden sheds).

Mind you, the only sawmills that will be allowed to process the wood are those with approved bio-security measures. And, in a move reminiscent of the foot-and-mouth outbreak, everyone visiting or working on an infected site is required to sluice down their boots, even bicycle tyres and to spray them with a PR-neutralizing chemical.

As for the tree offcuts (bark, branches and twigs), they represent too much of a risk to be recycled as garden mulch, or even sawdust; instead, they will be consigned to an eco-furnace and used as bio fuel.

But will all this be enough? Come the start of April, when larch needles reappear and, with them, the more visible signs of infection, the Forestry Commission is planning helicopter reconnaissance, to see if PR is still with us (the pathogen affects the tops of the trees first).

The big fear is that it will spread to other species. In America, the syndrome is known as Sudden Oak Death (SOD) but so far, the two main genera of British oak (sessile and pedunculate) have demonstrated a resistance that their American cousins have been unable to muster.

There is, however, no guarantee of any kind, and Sod’s Law may well dictate that, even if every larch in Britain is destroyed, the pathogen will skip to blueberries or even heather (a distinct possibility, it is feared).

So despite having mounted a comprehensive cull in a commendably short time, the commission acknowledges a certain powerlessness. “The indications are that we will have to learn to live with this pathogen, and do our best to minimize its impact,” says Roddie Burgess, its head of plant health. “It is unlikely now that we can eradicate this pathogen in woodlands. Can we contain it? I’d say we still have a fighting chance.”

To find out more, visit the PR section of the Forestry Commission website, at www.forestry.gov.uk/pramorum

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