Tree Pests and Diseases

Earl of Devon Excerpts

Thursday 13th February 2020 Lords Chamber

[Earl of Devon (CB)]

My Lords, I, too, am grateful both to the noble Earl, Lord Kinnoull, and to the noble and learned Lord, Lord Hope, for first pursuing, and then persevering with, this crucial debate. I am pleased that it has survived both the pest of Prorogation and the Disease of dissolution to make its way to the Floor of your Lordships’ House.

The delay does not make the debate any less urgent: it is more important now than ever. The past six months have seen an escalation in the epidemic of disease impacting our woods. We have also endured a brutal winter of floods, followed by violent storms that destroyed many mature trees weakened by illness. Meanwhile, we have been glibly promised by every major party manifesto an unprecedented level of tree planting in support of net-zero ambitions, but without commitments to undertake the complex research and investment necessary to deliver on such promises.

We hear much about sustainability, but hear no practical plan of what trees to plant, where to plant them, or how to protect them from an early, disease-ridden death. It is sad that more than 300 years after Hans Carl von Carlowitz first coined the term “sustainability” in preserving Germany’s forests, we hear the term bandied about by politicians to greenwash campaigns, but without appreciation of what sustainability costs.

I declare my interests as steward of a family-owned SME that has depended on and nurtured trees since the Middle Ages. I am also, regrettably, subject to statutory plant health notices due to chestnut blight in our ancient woods. Chestnut blight is a pernicious fungal disease that is fatal to sweet chestnuts—a naturalised, not native species. Since its introduction by the Romans, or possibly earlier, the tree has been prized for its nuts, its versatile timber, and its beautiful twisted bark. One of Powderham’s oldest inhabitants is a squat, stag-headed sweet chestnut, planted shortly after the Civil War. It may not live much longer.

Chestnut blight originated in Asia and, after accidental introduction to North America, killed 3.5 billion trees last century, decimating the species on that continent; it has been present in Europe for at least the last half-century. It was first discovered in England in 2011 and was first found within a mature woodland setting at Powderham in 2017. Since then, I have learned more than I would ever wish to know about crypho- nectria parasitica.

It was introduced under a well-intentioned, government-supported planting campaign back in the 1990s. My father was a keen forester and, after felling a block of mature oaks, he replanted chestnut purchased from a reputable nursery. That nursery had sourced its stock from Belgium, which is how the disease entered the country. One of the more impressive aspects of this sad story is the speed with which the Forestry Commission was able to track other chestnuts from the same stock; within weeks, the disease was confirmed across southern England. Served with an SPHN, we worked with the commission to determine a course of action. Our first plan was eradication, and all the 1990s chestnuts were removed and burned. It soon became apparent that the disease was in the wider woodland and therefore, in spring 2019, we felled over 100 mature chestnuts, each over 100 years old: that is more than 10,000 years of tree growth.

The heartwood was cut into sleepers; the rest of each tree was burned on site. A little revenue was thus generated which, together with a restocking grant, meant that the process was marginally cost-negative. To lose money like this felling centuries-old timber was heart-breaking and nonsensical, both for my pocket and for national tree health. While Powderham is able to absorb the loss, other landholders would be severely financially distressed in such circumstances, through no fault of their own. Without better emergency funding, land managers will be discouraged from reporting suspected disease for fear of the punitive costs of eradication.

Recently, blight has been identified in yet more trees. In fact, the experts are on site today to determine the extent; we must assume it is everywhere. Recommendations have changed: given the extent of the disease, we are no longer seeking eradication, preferring to pray for genetic resilience or a viral counterinsurgency. The remaining chestnuts might thus be given a reprieve to live out their days diseased but at least upright.

I am grateful for the hard work of the Forestry Commission and its tireless team of foresters and scientists, but they are hopelessly overstretched and underresourced for the war they are waging. I described it previously as “a losing game of whack-a-mole”, as every time I have seen people from the commission—and it has been all too rare over the last two years—they have been rushed off their feet dealing with yet another disease outbreak. If the Government are really serious about planting more than 30 million trees each year, they simply have to invest more in border biosecurity, in the commission itself, and in the development of healthy nursery stock. They might also have to restrict public access to woodland to prevent the further spread of disease. Will they do so?

To plant that many trees, we will have to import seedlings and saplings in vast numbers, as we simply cannot generate such stock on this island. That will only increase the likelihood of disease if we do not proactively manage it. We must also decide what to plant. My daughter is here today, and one thing I am determined to avoid is leaving her with either diseased and dying broadleafs of no commercial value, or a barren coniferous monoculture of no ecological value. I am searching for a suitable broadleaf species to replace the chestnut, but simply cannot find anything suitable that can grow in a warming climate that is not at risk from disease or pestilence, particularly squirrels.

In finishing, I would like to offer some warning words from the past on squirrels, as I know it is a favoured subject. Much demonisation is rightly directed to the grey squirrel, but, in their partial defence, I would like to quote a letter we recently unearthed. Written in 1825 by John Wilkinson, it is an agent’s report to the gay, and thus exiled, 3rd Viscount Courtenay:

“The noble range of new plantation at Mellands must be pronounced by everyone who sees it ... as a most striking improvement ... with the exception of the upper part which ... partly from the depredations of our old friends the rabbits is not in so thriving a state ... I was much grieved however to remark the very serious injury done to the Scotch firs by another description of marauders than the rabbits viz the squirrels. There are scores and I may also say hundreds of those firs completely destroyed by these animals which I saw running about in every direction. I did not hesitate to giving the strictest injunctions I could to Wilcox and his brother gamekeeper to destroy them or at least to diminish their numbers.”


Given that this was written 50 years before the introduction of the grey squirrel, these marauders are clearly our native red squirrel. The letter thus reveals that whatever species of squirrel is present requires proactive and determined management to avoid serious pestilence to our native trees. Are the Government prepared for this?