Brown patches on thuya

niamh flanagan asked 13 years ago

I have over 20 cone shaped/ pyramid shaped conifers ? arborvitae holmstrup or emerald.They are about 6 ft in height and were planted over 6 years ago.In the last few weeks brown patches have appeared at the bottom of the trees and has spread throughout 2/3 of the trees. While on other trees areas at the bottom of the tree have turned black in colour as if they were burnt .Could you please tell me what has caused this and what i can do to treat it . Thanking you.

1 Answers

Gerry Daly Staff answered 3 years ago
Thuya and any other pillar-clipped tree are susceptible to the attentions of male dogs marking their territory. This is very common and the most obvious explanation. If there is absolutely no access for dogs, stray or otherwise, it is possible that this is thuya needle scorch, a fungal disease which caused the foliage to go brown and patchy. 

There is no controlfor this, but it is worst in damp weather and where there is not enough air movement.

The blackening of foliage might be due to the presence of greenflies which shed honeydew on which sooty moulds grow. These sooty moulds ar enot harmful and disappear when the honeydew producers go.