Tree Pests and Diseases

Lord Colgrain Excerpts

Thursday 13th February 2020 Lords Chamber

[Lord Colgrain (Con)]

My Lords, it is sobering to consider that not many of us alive today remember what the English countryside looked like before the ravages of Dutch elm disease. It is for those of us who do remember to draw a parallel between that cataclysm and the one we are told is about to descend on us with ash dieback, which I think will alter the countryside to a far greater degree than most can appreciate. It is timely that we are having this debate, and I congratulate my noble and learned friend Lord Hope and the noble Earl, Lord Kinnoull, on securing it.

I served recently on your Lordships’ ad hoc Rural Economy Committee. In our report we laid emphasis on the importance of a place-based approach. This is particularly true of any discussion about woodland tree pests and diseases, where my personal experience and observations relate specifically to Kent. We have two tree types most at risk from disease: the native oak, and the sweet chestnut, historically an import but which has now become part of our woodland vernacular.

With the Chatham dockyard nearby and the oaks of England providing the crucial first line of defence in the construction of ships of the line for the Royal Navy from Elizabethan to Napoleonic times, oaks and Kent come naturally in the same sentence. Oak dieback and acute oak decline have been evident for a number of years. We have an ongoing monitoring programme, and in many instances it seems difficult to distinguish dieback from the other diseases from which the oak suffers, such as defoliation by the oak processionary moth. Certain gradual and sudden deaths are problematic to diagnose, with some people maintaining that perhaps certain individual trees have been weakened by the effects of global warming—on which I have my doubts. Oak and ash trees dying across our landscape would make it nigh on unrecognisable, and any science that can be funded to help arrest such a tragedy should be hugely encouraged.

Kent has many tens of thousands of acres of sweet chestnut, a versatile wood used historically for pit props in east Kent coalfields, hop poles when we had a vibrant beer industry, charcoal when London depended on that fuel source, and fencing materials. It is still valued for the last and is an excellent biomass fuel source, given the intensity of its burn. The arrival of sweet chestnut blight has given us cause for huge concern. While it seems to be contained currently, it has brought home the need for the proper monitoring of imports and for endless in-field or in-wood vigilance.

Those who lived through the great storm of 1987 remember its immediate effects, but those who were in the eye of it continue to live with its consequences. For us in west Kent, the obliteration of the deer fences at the National Trust’s Knole Park resulted in the introduction to the locality of a fallow deer herd population that has been impossible to control. The effect on natural regeneration of native woodland has been devastating and catastrophic, as has the effect on ground-nesting birds when all natural cover has been grazed away. There are said to be more deer in England now than at any time in our history, which will have a severely detrimental effect on self-sown and self-selecting species. Advocates of rewilding who want to include the introduction of deer in that process should realise the disadvantages this can produce.

However, the foreign invader that has taken most advantage of the devastation wrought by the storm is the rhododendron ponticum, another persistent and vigorous invader that leaves a barren undercanopy that is hostile to all our native fauna and flora. Along with other plants introduced originally for Victorian gardens, such as Japanese knotweed, it is expensive and time-consuming to deal with and should be in the bull’s-eye for any new forestry grant programme that emanates from the Agriculture Bill.

Last but by no means least is the destroyer of much new tree growth, the grey squirrel—evidenced by brown strips of barked saplings and dead new growth in plantation and coppice—another pest introduced for aesthetic reasons with no appreciation of the damage it could do if left unchecked, not least to our native red squirrel, birds’ eggs and unfledged chicks. It seems we are unable to control it—a view that probably has much in common with the prevailing wisdom of our grandparents’ generation about the rabbit, which in its millions was devastating field and woodland crops. That was controlled in the end by the advent of myxomatosis. Let us hope that scientists can come up with a more humane solution for the grey squirrel, but a solution there must be if we are to encourage a vibrant commercial woodland industry.

We can expect to have to deal with natural and weather-related disasters, and we are at the mercy of windborne spores and pests, such as ash cholera and the box moth, but what we can prevent we must guard against, such as the import of disease on young plants and the release into the wild of animals that will upset our wonderful, historic, native ecosystem. We should also guard against our own ill-thought-out measures such as plastic tree guards, which blight our woodland for decades and leave permanent pollution.