A further look at a lawson cypress with dieback

Earlier this week I posted this short piece about a Lawson cypress I had come across, which was exhibiting significant signs of dieback – nearly all of which was on one side of the crown.

Today, I returned to inspect the tree more closely, and took the below pictures. From the images, and looking through Diagnosis of ill-health in trees, I am leaning more towards either Cinara cupressi (cypress aphid) or Phytophthora spp.

My reasons for suspecting the former revolve around the fact dieback on the healthier side of the crown is principally at the bottom, which is suggested as a symptom as a result of aphid colonisation. Looking at the RHS website, the shown image also correlates with what was evident within the crown of this Lawson cypress.

However, as described in Diagnosis of ill-health in trees, Phytophthora spp. may likely kill just one side of a tree’s crown – this is absolutely the case here, if you refer back to my previous post on the topic to view pictures of the overall crown. Additionally, the roots seem to be sound, which is another symptom of (non-)damage by this pathogen.

If anyone has any thoughts on exactly what this may be, please leave a comment below. I am very keen to find out, as another Lawson cypress nearby is starting to show similar signs on one side of its lower crown.

The upper crown on the healthy stem appears to be without damage, though the lower region of the crown is visibily suffering.

Looking more closely, there is some distinct thinning as well. However, I wouldn’t say this is the ‘flagging’ that is associated with seiridium canker.

Closer still we move in, and the extent of the dieback becomes very apparent.

From inspecting one small region of the crown, it is evident that the youngest shoot growth is dead, whilst earlier growth remains alive – for now.