The Three Fates of Coed Y Brenin

Part Three: Plague.

For those of us of a certain age, we in the UK have already witnessed the loss of an entire tree species to disease, notably Dutch Elm Disease (ophiostoma novo-ulmi) which spread rapidly in the 1960s and 1970s and killed more than 20 million elms across the country; the Wildlife trust estimated there were some 1,000 mature elms left in the UK in 2016. More recently we have had chalara dieback of ash (chalara fraxina) but the occurrence of the phytophthora species present a far more serious and widespread challenge to those of us who plant and manage trees and a very serious threat to the whole idea of carbon sequestration in timber.

To begin with ash dieback, here at Penrhos it was one of the few trees I never needed to plant as we have several big, old specimens whose winged seeds have blown across the holding for decades, lodged, sprung up and until recently, flourished. One of my favourite trees, due to its excellent timber, remarkably fast growth rate and readiness to coppice, it has been an annual task to remove saplings from the garden and relocate them somewhere more useful.

above: medium sized ash growing with an oak, here at Penrhos and showing signs of dieback at the crown. Note the panic growth and presence of ivy, hinting something is wrong.

Not so now; dieback showed up first in the younger specimens but it was not long before larger trees began to show signs. Medium sized trees were the first to fail completely here, losing branches and then stems to the plague before dying. Now it has begun to effect our large ash, showing dieback amongst the branches, high in the canopy. The young saplings still appear but struggle immediately and don't survive for long.

Ash was renowned for the ease with which it can be split, a property that could make felling risky anyway. Now, infected trees, which may show few or no outward symptoms of the disease, have become extremely dangerous to deal with as the timber is severely weakened and may split or shatter unexpectedly. Reports of accidents when felling ash have increased in recent years and a number of woodsman have died tragically, including one of my oldest and best friends here on the Mawddach. Ash was not planted in Coed Y Brenin but there were many that had survived in old hedges or by the various riversides or simply blew in on the winds; it is not easy to find a plant that is not suffering to a greater or lesser extent.

above: Lyn with ash root - she’d left a bag of horse muck out on the field for a year or so and it happened to be on top of an ash root from one of our big trees. The root broke into the bag and devoured the horse muck, completely. I know its not really anything to do with this piece but I felt we needed at least one nice picture in this sorry tale...

The phytophthora species are a seriously odd lot, a “microscopic fungal-like organisms closely related to algae. Their name literally means ’the plant-destroyer’ and they have been responsible for some of the worst plant disease epidemics in history, including potato blight which led to the disastrous Irish potato famine in the 1800s.”¹

Phytophthora ramorum first appeared in the UK in 2002, on an imported Viburnum plant but its ultimate origins are unknown. The global plant trade is responsible for spreading it around the world, unfortunately not an unusual occurrence. The spores can be spread up to four miles by wind driven rain, they land on leaves and grow into susceptible trees by breaking down the cell walls which causes the initial blackening symptoms. It then grows within the tree and blocks their water transport system, leading to dieback and eventual death, meanwhile spreading to other trees.

above: larch coupes poisoned by CNC/NRW in advance of the plague. Note the grey patch in the middle distance and another patch nearer.

Its sometimes referred to as Larch Disease as the species is very susceptible but this is a bit of a misnomer as it has been found in over a hundred and fifty different species of trees, shrubs and other plants, including English oak, sessile oak, sweet chestnut, beech, sycamore, horse chestnut, cherry, ash and birch to name just a few. It is found now throughout the UK but is most severe in the west- think wet and windy...²

As of 2021, over 4000 sites have been investigated by Cyfoeth Naturiol Cymru/Natural Resources Wales (CNC/NRW) and 14,400 hectares of larch found affected by this pathogen, on both private and public land. Phytophthora ramorum manifested first in Coed Y Brenin some ten years ago in a large larch coupé in the north of the forest and rapidly spread from there. Aware of it from the start I immediately began felling the larch I had planted trying to keep in advance of the spread of the disease.

To go back a bit, after discussions with David Holmgren (co-founder of permaculture design) when he taught at our place in the mid 1990s, one third of the trees I planted were long term, high value species, such as oak, one third were fast growing, “harvest in your own lifetime” trees and one third were support trees, such as nitrogen fixers like alder.

I included larch in my fast growing “harvest in your own lifetime” third and planted lots. I favoured it, as a conifer, for it is unusual in being deciduous which means that apart from dumping a considerable amount of material annually, you can grow other stuff under it, including grasses, hence animals can graze under the boughs. Although it is not the way I wanted it, I suppose that here at Penrhos it did achieve what I intended and was harvested in my lifetime.

above: poisoned larch, felled and awiting felling. Note also the usual overtall, unthinned, restricted root space, a tribute to the Forestry Commission’s “do nothing” approach.

Because of larch's susceptibility to phytophthora ramorum it has been relatively easy to track the spread of the disease through Coed Y Brenin over the last decade; the needles turn an unusual brown during the growing season and more of the tree is affected each year until death occurs after a few seasons. It took a few years to move up the road that borders our place and claimed a couple of self-seeded larch on Argel, the wilderness patch, that I had not got round to felling.

CNC/NRW, well aware of the danger, has taken radical action, deliberately killing with poison all larch before the arrival of the disease in an attempt to stop the spread to other susceptible species. Unfortunately, larch was planted very widely, not just in Coed Y Brenin but throughout Cymru, in both large and small stands and the fact that the tree grows readily from small seed that can be carried by the wind means that isolated plants are present pretty much throughout the forest and beyond. These isolated trees can now be spotted amongst the green canopy as they turn brown and die.

CNC/NRW took over from the Forestry Commission Wales in 2013; it is a huge organisation and forestry plays only a small part in its very broad remit. I will look in more depth at NRW in a future piece but for now its sufficient to say that compared to the workforce of the old Forestry Commission Wales, the numbers of people involved in forest operations are considerably lower, meaning they are stretched to complete ordinary forest operations, such as thinning and rely extensively upon contractors.

NRW have been and will be felling larch for several years to come, as rapidly as possibly but this is a massive operation and is consuming most of the forest operation side of NRW's time and attention; in all, over six million larch trees will be felled in Cymru. Due to the complexity of the planting of tree species in Coed Y Brenin, something which made it much more interesting than many more monocultural, exotic plantations, stands of larch, some of which are quite small, are dotted throughout the core block and beyond. Add to this the fact that larch were also planted on extremely steep hillsides (elltydd) and the felling and extraction becomes more difficult, time consuming and hence expensive.

above: ridculously steep slope with no access that should never have been planted, now cleared of dead larch. Extraction is by way of a skyline, winching the trees up the slope. Note felled larch left of centre awaiting their turn.

Phytophthora ramomum means the end of larch in the UK, a tragedy in itself but there is a considerable risk that the disease may become similarly aggressive in other species and in 2015 infected sweet chestnut trees were spotted in as yet small numbers in Devon and Cornwall.

above: erosion in gulley after hauling felled timber up the slope. Wait till it rains…

As if this wasn't hard enough, another variation of phytophthora, phytophthora pluvialis³ was found in a Cornish woodland in 2021. In 2022, at an open day with NRW staff in our village hall, I was told that pluvialis had already appeared in Dovey Forest, some twenty miles or so to the south of us. This variety targets the few species that ramomum does less well with, namely Western Hemlock, Douglas Fir and various pine species including radiata pine (pinus radiata). Pluvialis has now been found in Coed Y Brenin.

These types of diseases are extremely difficult to contain, given that they are spread by wind blown rain. Rainwater dripping from infected trees will carry spores onto vehicles, machinery, clothing and the like and its not hard to imagine the transference of spores from there to other plants through physical contact or spray from tyres. The steady movement of phytophthora ramorum up the council road bordering us was quite clear, as one by one the foliage of the occasional self seeded larch turned brown, in progression, over several seasons.

There seems little doubt that the increase in visitor numbers has not helped and it would not surprise me if we find that one of the main vectors for the spread of the phytophthora species are mountain bikes, for mountain bike trails wind throughout the Core Block of Coed Y Brenin and beyond and the Dovey Forest is the same. Mountain bikers often try out trails in different forests and will inevitably carry traces of the plague with them. So too with forestry equipment such as the harvesters and forwarders that deal with infected trees.

At present, disease control on site is minimal, to say the least; on one site near us it was limited to a single sign advising workers to clean their boots on leaving the area, though no method of doing this was provided and no mention was made of their own vehicles or the forestry machinery. The single sign has since disappeared. In their virtual workshop⁴, CNC/NRW point out to visitors “that mud on your boots and clothing can spread the disease. We encourage you to wash your boots and clothing at home after visiting our woodlands.” Be warned, though, if you grow trees, or are visiting other sites with trees, it might be worth washing your boots and clothing before you go home...

To date there is no effective method developed for treating the disease and unfortunately, Phytophthora ramorum is here to stay and its also unlikely to be the last disease to appear as global warming continues to change our climate.

So there we have it- three possible fates for Coed Y Brenin and beyond- fire, wind and plague. Though it might seem hopeless at times, there are actions we can take to reduce these impacts and next time I will look in some detail at what we could do.

Thanks for reading.

1. The Woodland Trust’s concise descritption of phytophthora ramorum can be found here.

2. Defra lists the species in the UK that phytophthora ramorum has been found in. You can download the pdf here.

3. The UK Government’s Forest Research description of phytophthora pluvialis.

4. pdf download of CNC/NRWs very thorough virtual workshop on the phytophthora species.