Leylandii with white bark

Jamie Penman-Smithson · December 2014

We have two fir trees (I think they are leylandii) which were planted just over 20 years ago and in recent years have started to thin out in the middle. We had a tree surgeon take a look and he said that it was normal in fir trees for the middle to thin out.

When I was digging over the soil in the area next to them, I noticed that on one of the trees the bark near the soil level is covered in a white flaky substance, I can only find it on one side of the bark:

I can only find it on the larger tree, it's not affecting the smaller one.

Is this something to worry about or is it normal? Any advice would be appreciated.

Thanks very much,

Jamie