Ash Dieback: What’s causing the rise in plant diseases?

by Nathan Smith

Ash Dieback is the latest craze sweeping the nation, and by ‘craze’ I of course mean ‘plant disease’. Like Dutch Elm disease before it, it threatens to destroy thousands of iconic trees and restructure the shape of British woodland.

Caused by the fungus Chalara Fraxinea, Ash Dieback was first noticed in Poland in 1992, though it is thought to have originated somewhere in Asia. It affects the crown of the tree (the bushy top bit) and causes it to die back, although it may not kill a mature tree for a number of years. Even then it is often the case that when a tree is killed it is through an opportunistic infection. C. Fraxinea may not kill, but it does significantly weaken the tree.

AshAttributedSo what’s to blame? Despite fears that the fungus may have come to the UK via infected plants in nurseries, the current view is that it came in the wind from Europe (at least in the majority of cases of the disease). Whilst this may seem good news (particularly for the people running the nurseries), it causes us to reach a depressing conclusionwe cannot ‘stop’ the disease. The reasoning behind this is that most plant diseases can be controlled in the early stages of an outbreak via selective removal of plants. These techniques will probably not work now: we are in the middle of a full blown Europe-wide pandemic and even if we could remove the disease from the UK, it could still come back on the wind from across the seas. This may all sound rather despairing, and work is being done to try and reduce the ecological damage, but the truth is the models still predict that in 10-20 years time the majority of ash trees will be infected, if not already dead.

In a world of increasing globalisation, ensuring plant security from biological threats is almost impossible. Whether from the soil on a backpacker’s shoe or on a tree imported from afar, new microbes will always be brought into environments they have not come across before. Ash Dieback is not the first major tree disease to affect the UK and it’s probably safe to say it will not be the last.

For all those interested in some light reading, please find the link for the Government’s plan on tackling Ash Dieback:

Planet: Why Plants Matter

by Toby McMaster

As a world we currently face many major problems, to which we have yet to find specific solutions. The answers to many of these lie, at least partially, in plants. The first land plants appeared roughly 450 million years ago, primates around 80 million years ago and the first Homo sapiens only about 450,000 years ago. In short, for every year humans have inhabited planet Earth, land plants have inhabited it for a millenium. In fact, it seems likely that however hard we try to ruin our planet for ourselves, some vegetation will still outlive us. In the history book of plants, humans may yet just appear as a brief speck – a self-destructive species that got too big for its evolutionary boots and brought entire ecosystems tumbling down with it. Plants are here to stay – so why not use them to try and ensure that we are too? In this first blog entry we will explore the various ways in which plants can help us overcome the issues facing humankind.

Climate Change

AttributedEarthWith the recent IPCC report on climate change delivering a figure of 95% certainty that humans are causing the current rise in global temperature, it is surely necessary to act to mitigate the situation, even if only as a precaution. Given that 15% of atmospheric CO2passes through plants each year, they are certain to play a role if we are to keep global warming to a minimum. We desperately need a better understanding of the likely worldwide effects of climate change on plant life and to try to work out what we can do to minimise any damage such changes will cause.

Starvation and Malnutrition

According to the World Health Organisation, 842 million people in the world do not have enough to eat. 827 million of these people live in developing countries. The UN predicts that by 2050 the world population will reach 9.6 billion. Moreover that of developed regions is forecast to remain largely unchanged at around 1.3 billion from now until then while the 49 least developed countries are expected to double in size from around 900 million people in 2013 to 1.8 billion in 2050. This will lead to widespread hunger we can’t understand on a scale we can’t understand. These are an intimidating set of circumstances but as a planet we can rise to the challenge. To do this will require improving both crop yields and food distribution, and reducing waste. The fact is that as a massive proportion of the Earth’s ecological base plants represent the most efficient way to feed more people faster. To utilise them we need to explore all the techniques available to us, GM is undoubtedly one of these but is far from a magic bullet, we also need to put as many resources as we can into understanding how to optimise agriculture.


BDWe are currently in the middle of the 6th mass extinction event in the history of our planet, and the first since 65 million years ago when the dinosaurs were wiped from the face of the Earth. Species are going extinct at somewhere between 100 and 1000 times the expected background rate. It is arguably unethical for our one species to have eliminated so many others, but in one sense extinction is a natural process we have merely accelerated through habitat destruction and climate change. The real issue is that we are reliant on so many species which are in danger of extinction and that we are rapidly losing the opportunities, including novel medicines, offered by so many more.

The approach taken in the past has often been based on the naïve human view that we can just hang on to the species we are interested in and let the remainder of the natural world disappear into oblivion. This is misguided for two main reasons: firstly, our knowledge of the natural world is nowhere near sufficient to rule out species as useless to us, and secondly, species do not exist in isolation but rather as complex ecosytems to be viewed as cohesive units. Plants will represent a massive part of future attempts at restorative ecology – trying to rebuild damaged ecosystems. They must also be carefully protected in the functional ecosystems we still have, as they are so often the foundation stone on which the rest of the community is built.


AttributedMedicineIn an age where we have complex techniques such as X-ray crystallography to help probe molecular structures, we might like to think we are beyond simply taking compounds plants have already made for us, and using these chemicals to treat disease. Nothing could be further from the truth. According to the American Association for the Advancement of Science (AAAS) in the year 2000 around 25 percent of prescription drugs dispensed in the United States contain plant extracts or active ingredients derived from plants, and more than 60 percent of cancer drugs on the market were based at least in part on natural products. These are, admittedly, not incredibly recent statistics, but the timescale over which new drug discovery and production takes place means they are likely still approximately accurate. There are still countless conditions and diseases for which we have no or poor treatments, and plants will have a massive role to play in helping fight these ailments.

As demonstrated by the last two examples in particular, these problems are not isolated from each other. Plummeting biodiversity is cutting down our supply of potential new medicines, medicines which we will need to help treat a booming population in developing nations where mortality rates from infectious disease rates are highest. Any new drugs will likely be incredibly expensive to begin with, a problem which may be compounded by the economic impact of climate change on developing countries.

This is only a short list of the problems we face and plants may well not hold the solution to all of them, but they are an incredible natural resource which we should make use of. This blog is dedicated to discussing the ways in which we can do this, and to generating enthusiasm for plant science research.