Tree Pests and Diseases

Lord Hope of Craighead Excerpts
Thursday 13th February 2020

(4 years, 1 month ago)

Lords Chamber
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Moved by
Lord Hope of Craighead Portrait Lord Hope of Craighead
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That this House takes note of the threats posed by pests and diseases to native trees in the United Kingdom.

Lord Hope of Craighead Portrait Lord Hope of Craighead (CB)
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My Lords, it is a real privilege for me to have been asked to open this debate. Before I go any further, I should explain that I am doing so on behalf of the noble Earl, Lord Kinnoull, who I am glad to see in his place. It was his idea, and he secured the debate just before his appointment as chairman of the EU Committee made it impossible for him to open it himself. That is why I am speaking now. I can only hope that I can do justice to this crucially important subject in the time available. Of course, I look forward very much indeed to hear what he will have to say when his turn comes to speak, and I know that it is largely due to his initiative that so many noble Lords have put their names down to speak—and many noble Lords have told me that they were unable to do so because of time constraints. So it is a very important subject, which has been well recognised.

The issue to which the Motion draws attention is sadly all too familiar to those of us who care about the countryside and the creatures, including the plants and trees, that are to be found there. The threats posed by non-native animals which become pests is not a new issue. As long ago as 1935, Evelyn Baxter and Leonora Rintoul, in their book A Vertebrate Fauna of Forth, noted that the spread of the grey squirrel in their part of Scotland was likely to be troublesome, and that a good many complaints had already been made about the damage done to trees by that animal. It is now recognised that the grey squirrel is at the top of the list of the introduced species which are regarded as pests that are damaging, especially to trees.

The damage done to ground-nesting birds by another species imported from North America, the mink, has caused great concern. It is only now being brought under control by eliminating that animal from places where it has caused the most damage, particularly the Outer Hebrides. The devastating effect on native species in our rivers by the introduction of signal crayfish from North America to combat European crayfish disease is another example. Then there is the threat to trees caused by tree pests and tree diseases.

There is of course an aesthetic aspect to this problem. No one likes to see dead or dying trees. I think the elms were the first to go; their sad and empty corpses still stand along the edges of fields, as there is no profit to be made from cutting them down. About 35 years ago, acute oak decline made its appearance, and more recently the oak processionary moth, which causes rashes and breathing difficulties for some people and animals, arrived here in 2005. We have also seen the devastating effects of the fungus that causes ash dieback, especially among young trees, which have been planted to improve the contribution that deciduous woodlands make to our environment.

These pests and diseases have wider effects, too. Trees, after all, are part of a much larger ecosystem that includes the birds, animals and insects that inhabit them. When the trees die, the adverse effects extend well beyond the trees themselves. We are fortunate at Craighead, at 1,100 feet in the hills of north-east Perthshire. About 150 years ago, five trees were planted beside the shepherd’s moorland cottage that we now own. They consist of two sycamores, two ash trees and one elm. I hope that I am not tempting fate when I say that they all remain in good health. Indeed, the elm recently seeded a baby elm, which too is doing well. We have planted numerous other trees ourselves—alder, rowan and birch. They provide shelter for a variety of warblers and finches, which we did not have around us before they were planted, but it is the old trees that are the most important for our ecology.

Many birds and numerous insects inhabit them. Most entertaining are the crossbills, which bring their recently fledged young in early spring—just about now in February—to nibble the buds of our ash trees. The young ones do not have cross bills, so nibbling ash trees is much easier than trying to grapple with a pine cone. A pair of starlings nests each year in a hole in one of the ash trees, and swallows circle around all five trees in the summer, picking up the many insects that they attract. The trees are a place of refuge for a variety of ground-feeding birds, which are at risk of being picked off, when out in the open, by a passing merlin or sparrowhawk. So much of that activity would be lost to us if our old trees were to die. This is just a tiny glimpse of a very much larger problem spread throughout the United Kingdom.

It is possible to attribute the arrival of such pests and diseases into the UK to two causes. One is the force of nature itself. By that I mean that they are carried to these shores by birds and insects blown across the sea from continental Europe. There is not much we can do about that, other than to keep our eyes open and seek to eliminate the risk of their spreading by careful management and research into how to tackle them, as much as we can. Birds move around, after all, and the migration of insect species, such as the painted lady butterfly, shows that insects move around too.

The origin of the spread of alien diseases to our native trees, such as the non-native fungus that causes ash dieback and acute oak decline, is not easy to determine. It seems likely that the force of nature had something to do with it, but we must accept part of the blame too, as too little attention was given, in the past, to keeping our eyes open and preventing them gaining a foothold here.

The other cause we must face is misguided or careless human activity. Importing sapling trees from abroad risks bringing alien diseases with them, as well as pests. We have something to learn from the way that controls are imposed by the authorities in New Zealand on the importation into that country of any plant, seed or other vegetable material. The biosecurity controls at their airports far exceed those in operation in the United Kingdom, as I once discovered when I arrived in that country having in my bag a rather attractive and innocent-looking pine cone. I had picked it up on holiday in southern California. I was warned by a form, which I had to complete, to declare any such items on arrival. I duly did so, only to find that I was being treated almost as if I were a criminal. I was escorted on arrival to an office, where the pine cone was impounded. It was sealed inside a plastic bag by an officer wearing rubber gloves, who was distinctly unfriendly, and placed in quarantine. Moreover, I was ordered to sign a form giving my flight details and undertaking to collect it on my way out. Doing that took a lot of time and I nearly missed my flight home. They assumed of course that I would declare my pine cone to the authorities on my return to the United Kingdom, but, on my arrival, I could not see anyone to whom I could declare it—so, I am ashamed to say, I never did.

Now we are about to embark on a major expansion of our woodlands in this country, as part of our contribution to combating climate change. Some idea of the scale of this project can be gathered from a recommendation of the Woodland Trust, which is such a force for good in this context, that 30 new trees should be planted to replace every single tree that has to be taken down for the development of HS2. I believe that this massive drive to plant new trees, however laudable on climate change grounds, carries with it real dangers. Let us hope that we can boost our native nursery production to keep pace with demand, and that the young stock that is used for this expansion is carefully chosen to see that it is free from alien diseases.

Leaving trees aside, we are all too familiar with the way the introduction of non-native species can affect the survival of those that are native to these islands. The grey squirrel is one example that I have given; American mink and signal crayfish are two more. Some of the worst examples of misguided human activity can be found in New Zealand and Australia, where serious damage has been caused by the uncontrolled spread of rabbits. The sad fact is that the introduction of a non-native species to control another can make matters worse—we have the example of the signal crayfish. In New Zealand, stoats were introduced to control the rabbits, but they soon devastated that country’s unique ground-nesting wildlife, which had evolved in the absence of any predatory land mammals.

Man’s introduction of non-native birds can be just as damaging. The common myna was introduced to control insect pests in Australia, but it has caused widespread damage to native birds in the competition for nesting sites. I do not think that the European blackbirds, song thrushes and yellowhammers, which seem to flourish in New Zealand, do any harm there, but the European starling is a real pest, as it is in some parts of North America. The cactus wren, which nests in holes in the tall saguaro cactus trees in Arizona, finds it hard to maintain its numbers in the face of competition for these holes from starlings. There are lessons for us in these examples: there are dangers in trying to control non-native pests by the introduction of non-native predators. This applies not just to animals and birds; the introduction of non-native insects to do the same thing can be just as damaging, unless care is taken to assess the effects before it is too late.

I worry about the recent introduction of the white-tailed sea eagle to Mull and other parts of the west Highlands. The return of the osprey, which is not man-assisted, is very welcome and I am not aware of any adverse consequences. One could say the same thing about the collared dove, which extended its range from eastern Europe with remarkable speed and reached us in the 1960s; but the sea eagle, whose return was man-assisted, preys extensively on lambs and is at risk of driving some sheep farmers out of business. Rewilding of this kind by the introduction of species that used to breed here is a romantic idea that seems unlikely to cause undue damage to our native wildlife, but it does have its dangers too.

Against that sad background, I very much welcome Defra’s tree health resilience strategy, which was published in May 2018. It was set up to reduce the risk of pest and disease threats to trees and increase their resilience to such threats. Among other things, the strategy is designed to establish common UK-wide approaches, along with the devolved Administrations, to plant health policy. Given that, I will seek four assurances from the Minister.

First, can we be assured that the action plan really is being put into practice and that the funding it needs to implement common rules and ways of working will be maintained well into the future, notwithstanding the effects of Brexit? Secondly, can we be assured that the budget for combating the importation of invasive species, which at present is a minute part of the total spend on biosecurity, will be increased to keep pace with the increasing challenges that we face, including the importation, if it continues, of new trees?

Thirdly, can we be assured that, now that we have left the EU, we will keep closely in touch with EU environmental law and that common approaches to retained EU law will be maintained with the devolved Administrations so that there will be no loopholes through which pests and diseases might creep? Fourthly, can the greatest care be taken to see that, when new woodlands are being planted here by private individuals, local bodies and other organisations, the trees that are chosen are taken from stock that has been grown in the British Isles, not imported from overseas, and that it is truly disease free? I beg to move.

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Lord Hope of Craighead Portrait Lord Hope of Craighead
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My Lords, on both my behalf and that of the noble Earl, Lord Kinnoull, I thank all noble Lords who have taken part in this fascinating and very important debate. I thank the Minister for a very detailed and helpful reply, which I am sure we will all want to study with some care when it appears in Hansard.

The debate has drawn attention in the most powerful way possible to the scale of the problem that we face. We have covered many parts of the country, from Devon, east Kent and Wiltshire to South Yorkshire, Wales and Scotland. We have heard detailed descriptions from people who really know what they are talking about of the problems that they face. Of course it is right to say that landowners bear a responsibility for looking after the trees that they have on their land, but the Government have a major part to play too because of the resources and powers that are available and the initiatives that they can take. I hope that what has come through the debate is the message that we look to the Government for initiatives, particularly in the realm of biodiversity, which will seek to address the problem.

There is a curious paradox here. Someone said, although I cannot remember who it was, that a person working in woodlands had said it was the safest job he had ever had because you do not see the results. It is a long-term process; trees take many years to develop. But the problems we face are the complete reverse; they are not long-term problems at all but urgent. It is very dangerous to think of planting wide areas of woodland when we face issues that could destroy them before they even have a chance to get going. So this is a major problem and an urgent one, but we can feel encouraged that the Minister will do his very best to respond to it.

I was very taken with the tribute paid by the noble Baroness, Lady Jones of Whitchurch, when she said that the Minister had done more than most to raise awareness of the impact of these diseases. I believe that is true. He is very well placed, because of his knowledge and experience, to carry forward the message that has come from this debate. We very much look forward to the results of that, which, as I say, are short-term, so many of us are young enough to see the results of that although we may not see the trees grow to their full potential. I beg to move.

Motion agreed.