Sunday 19 May 2013

Worrying Times

While doing a breeding bird survey on an upland square, between Mountain Ash and Aberfan, today, I was shocked at the condition of the Bilberry up there. The top of Mynydd Merthyr is dominated by Bilberry and acid grassland, with wetter, rushy areas. In July 2010, I found suspicious die-back in some Bilberry within the adjacent conifer forest and this was subsequently confirmed as being infected with Phytophthora ramorum, though this, it seems, was coincidental, as the plants were not showing the classic signs of Phytophthora infection and the symptoms I had noted were attributed to some sort of virulent leaf and stem spot fungus, unknown.

Those plants were sprayed with herbicide, together with a 10 metre buffer, but the leaf spot disease was already widespread and causing die-back on areas across the hill top. In 2011 and 2012, I noticed that the damage caused by the leaf spot, or Phytophthora was increasing gradually, but nothing prepared me for the devastation I saw today.

Infected Bilberry, with newly dead stems showing up red

More die-back

And more

The grey patches are Bilberry that was affected last year and the orange patches are this year's infected areas

More infected areas

On my way back down, every patch of Bilberry I saw was similarly affected and I've seen the leaf spot disease just about everywhere in Cynon and Merthyr. Whether it is the leaf spot or Phytophthora is affecting the Bilberry so severely, is slightly irrelevant. The point is, Bilberry in this area is in serious trouble and that will inevitably have a detrimental effect on Bilberry feeding or nectaring insects, as well as those species of bird that rely on their larvae for food.

All in all, the whole morning's walk  was a sobering and depressing affair, with the Bilberry, the dying Larch and also dying Birch, the latter being a particular worry.


  1. That is very worrying and certainly something I'll be looking out for this end of he county. I'll keep you posted...

  2. I haven't noticed any of this in the Llynfi valey Mark but i will certainly keep an eye out for it.

  3. Mark, have you informed the Phytophthora team?

  4. I informed Kevin Izzard of the early outbreak and took him up there twice, so that he could collect material for analysis, which is what confirmed the presence of Phytophthora and led to the spraying of a buffer zone.
    A few months ago, I received an email from Kevin informing me that the Phytophthora team were being disbanded: job done, or possibly undo-able, I suspect.
    What puzzles me most about this is that the Bilberry plants aren't showing the classic signs of phytophthora, such as the zebra stripes on the stems. The only symptoms prior to this die-back is red and purple spotting on the leaves and stems. If this isn't a previously unrecorded manifestation of Phytophthora symptoms, then this is a completely separate disease and if so, what is it and where did it come from?
    I have searched in vain for even a mention of a leaf spot disease of Vaccinium, which given the dramatic effects of the infection, seems odd. I even wondered whether it was something that has been imported into the UK with High Bush Blueberry plants, which have become popular in the last several years, but drew a blank there too. The only way to get to the bottom of it would be to try and get DEFRA to take material away for analysis.
    As I said, every patch of Bilberry I've looked at in the Cynon and Merthyr valleys are showing the leaf spotting, to a greater or lesser extent and many are showing signs of die-back from last year.