Monday, 22 December 2008

Scots Pine mystery

In one particular part of the young coniferous plantation, Scots Pine trees are growing in a peculiar manner. This is a shot of an affected tree:

Note the 'pom pom' effect on the branches.

Here's a close-up of an affected shoot:

The damage appears to be caused by clusters of needles dying and dropping off:

This shot shows that multiple areas of single plants are simultaneously affected:

I was told that the effect can be caused by the European Pine Sawfly, but my research shows that this sawfly damages needles in a completely different way: by eating them down to the branch. So it looks like I'm back to square one on this one.


Gill said...

Fascinating - is each pompom a year's growth, or are the damaged needles within one year's growth? Are all the affected trees in one area of the wood, in which case I would suspect some soil/water environmental effect (and in that case I might also expect other vegetation in the area to show peculiarities as well).

I have seen trees patchily defoliated (but not neatly like yours) in other places but that has been down to acid rain which I would not imagine is a problem in Donegal. Plain rain of course is another matter :-).

Intriguing - watch this space!

And Happy Christmas!

Stuart said...

Each gap appears to be a single year's growth...from a previous year. This started on one tree and is spreading outwards to neighbouring trees, so I think it's a pathogen, not environmental. Defoliation is never complete: there are always pompoms left. Wonder if it's fungal (I have a sample with dead needles on it on a slide...I'm waiting to see if there are any spores).