DOTHISTROMA NEEDLE BLIGHT  - In recent years, Scots pine has been badly affected by disease.  This can form needle discolouration and a significant slowing of growth, almost to the point of stand-still.

Diagnosis of DNB can be tricky as many other factors can cause temporary or permanent discolouration, so Forest Research has produced a useful field guide to help with identification and it also gives details on where to send samples for diagnosis.