On 09/06/2013 20:59, Tahiri wrote:
Can anyone suggest what might be killing this cotoneaster?

Hard to say since the bit you show appears to be coming into leaf fairly
normally. Need to see the diseased plant material, but it is susceptible
to fireblight which does characteristic damage and is obvious at this
time of year with parts looking like they have been scorched by fire and
then becoming dead wood quite rapidly.

http://www.bing.com/images/search?q=...electedIndex=1

That isn't a good picture of it either. If I remember I will try and
take a shot of a badly fireblight infected hedge at my brother in laws
next time I am visiting.

Is the white stuff lichen and if so is it cause or effect?

I think that is just lichen from age. Clean a white fluffy bit up with
some meths on a brush and if it is an insect pest like woolly aphid or
mealy bug you will see it when it is wetted with the meths.

The whole plant is going at once rather than a branch at a
time but the ones either side appear to be okay - so far!

http://www.tanygraig.force9.co.uk/E/...otoneaster.jpg
Sorry, but it is a reasonable size file in order to keep the detail.
T.

A picture of the dead and dying bit would be most helpful.

--
Regards,
Martin Brown