Reprinted from Newsletter 140, dated 2013 October

New fungal diseases threaten yet more of our trees JN

Sweet chestnut blight is characterized by cankers that spread all over the surface of the tree and eventually kill it. The cause is a fungus that began in eastern Asia. In the first half of the 20th century it eradicated sweet chestnut from eastern North America. In 2011 it was seen for the first time in Britain, and threatens thousands of acres of woodland in southern England where sweet chestnut is the dominant tree species. (The horse chestnut or conker tree is an unrelated species.)

We all remember how Dutch elm disease devastated the landscape by wiping out thousands of elms in the hedgerows all around us. Today it seems our trees are suffering an epidemic of a new disease every year.

  It’s a big concern to the Conservation Society, having planted nearly 48,000 trees in the area since its inception. How will these diseases affect us?

  The pictures show just three recently confirmed diseases that Guy Litchfield, of the Sussex agricultural college at Plumpton, will inform us about at the society’s [2013] AGM on Friday November 1.

  For a report of the talk, see Newsletter 141.

Chalara fraxinea, another fungus, causes a lethal disease of ash trees — ash dieback. It was detected for the first time in Britain in 2012 at a number of sites. Black blotches appear, often at the leaf base and midrib, and leaves wilt. It affects ash trees of all ages. These fungi are notifiable pathogens: suspected cases must be reported to the Forestry Commission.
Red band needle blight is so called because of the colourful symptoms the Dothistroma fungus causes on pine until the tree dies. It affected only the Southern Hemisphere until in the 1990s it began to spread rapidly in both Europe and in Canada, with major economic impact.
(Picture sources: Royal Horticultural Society, Forestry Commission, Uniprot)

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