Tuesday, 14 May 2013

If you go down to the woods today...'re sure of a big surprise. And no, it's not teddy bears.

There has been a great deal of news coverage in the last six months or so about the invasive Ash Dieback disease, which threatens to decimate our Ash populations if we do not find a way to control it or prevent its spread.
You may be forgiven for thinking that Ash Dieback was the only threat to our woodlands, such has been the media coverage, but other forest pathogens are also on the rampage, and they are set to change the landscape of my beautiful birthplace, the Forest of Dean.

PhD studies, a new husband, and living on the other side of the country were among the reasons I hadn't been back for a while, but just after Easter the call home became too strong, and I decided to go back and visit my old haunts for a day.

The Sculpture Trail was high on my list - 3.5 miles of woodland paths dotted with incredible sculptures inspired by local history and nature. As I started my ascent up the hill to 'Place', commonly known as the Giant's Chair, I looked forward to the view out across the forest that would greet me. I was saddened then, to see that the larch that had previously sloped down from the top of the hill had been felled, leaving barren space at the forefront of one of the Forest's best known viewpoints.

'Place' [source]

The trees had been felled in an attempt to stop the spread of oomycete pathogen Phytophthora ramorum which infects larch, oak, birch and sweet chestnut trees. News of this pathogen has been scarce of late, but in early 2013 its reach extended in Scotland. Cases are still being reported in the Forest of Dean and South Wales, despite attempts made to halt the spread of disease. It is suspected that the pathogen may be spreading via ornamental plants such as rhododendrons, impeding its containment.

As if that's not enough blight for my beloved Forest, I was recently made aware that yet another tree disease is making it's way through the woods. The iconic copse of evergreens on top of May Hill, which can be seen throughout Gloucestershire, may be destined for the chop, having fallen victim to Red Band Needle Blight - the Citizen newspaper reported last week. It particularly affects Corsican pines, which were planted in 1887 to mark Queen Victoria's Golden Jubilee. The Citizen have today reported that the older trees among the 99 that crown the hill may be spared, but younger trees are more susceptible to the disease.

May Hill - © Copyright Philip Halling
May Dawn [source]

This cluster of trees is where I brought in the new Millenium, and greeted the May Day dawn most years throughout my childhood to the sound of morris bells. The woods have a value to humanity far greater than that of timber or even ecosystem services. These diseases touch me not just as a plant pathologist, but because I feel a sense of belonging among the trees through which they spread.

I am frequently warned that forest pathology is not for the faint hearted and that crop pests are far easier to work with, but I am not sure you can take the Forest out of the girl, though she may be a long way from the Forest.

Save our vegetables! Why biosensing matters.

A couple of months ago (this says something about my blogging speed) the telegraph published an article describing a new fungal spore trap, which could in the future potentially be used to detect the deadly Ash Dieback fungus, and other foreign pathogens arriving on our shores.

What the Telegraph completely missed, however, was the importance of this invention for protection of our crops, not in the future, but now. The spore trap and coupled biosensor, designed by SYield consortium (funded by Syngenta and TSB) as a pilot project, has been specifically engineered to detect the spores of the deadly crop pathogen, Sclerotinia sclerotiorum.

Sclerotinia sclerotiorum is a soilborne fungus which is pathogenic to a wide range of agriculturally important plant species including carrots, beans, lettuce and oilseed rape. It causes stem and root rot, leading to crop damage and high yield losses where outbreaks occur.

Mmmmmm soggy carrots. [Source]

The nature of these outbreaks  is, however, sporadic, and with no way of predicting when Sclerotinia might strike, farmers have no choice but to adopt pre-emptive control measures, including routine preventative spraying of fungicides. While the cost of yield loss from failing to adequately protect crops is high, this prophylactic approach to disease management is also costly, both financially and ecologically: Production of fungicidal chemicals requires high energetic input, and their application may have negative environmental impacts. In addition to this, as with the overuse of antibiotics in human disease control, extensive use of fungicides may select for resistant strains of diseases, having a negative impact on future control.

In light of this, methods to detect agricultural pathogens in the field before they threaten crops are urgently needed in order to help farmers make decisions on whether and when to apply control measures. The early detection system developed by the SYield consortium may well provide a vital role in the future detection of invading tree diseases, but the importance of its application for detection of existing agricultural pathogens should not be overlooked.