Leylandii browning

Hello All, I am new to the forum but wonder if I can get soem help.

We have a large mature Leyelandii hedge along the boundary of our property. The hedge is approx 3.5M tall and approx 25 years old. Since early september the hedge has started to go brown in places and this is spreading. I was told it may be conifer aphid so a couple of weeks ago I spryed the hedge with Bayer Bug killer. This is not easy due to the size and density of hedge but I thought I gave it a good dousing. The prooblem still seems to be gettng worse though.
I have examined the hedge and cannot see any aphids and there is possibly only a bit of the sooty mould so I am not sure what to do.
Qustions are
1. If it is aphid, will they die anyway with the colder weather. If not is there another way to treat them.
2. If is not aphid what esle could it be?

Any help would be appreciated.

 

Hi DC......... ............


dont leyelandii go brown from the bottom naturally? when i had them, they did!

 

ello DC - I do'n't think this is caused by Aphids more likely the roots are drying out. We had a similar problem with or hedge which adjoined a road - another similar and similar age at the rear of the house was fine.
Sometimes you will see new growth coming through but not much of it in my experience - my only part cure was plenty of water...........

 

Thanks All

They are browning in patches midway up the trees and from the outer new growth back so looks like it may not aphid at all. I will try watering to see if that makes any difference, though they look healthy in the other areas i.e not wilting?

 

Nothing you can do, spraying trees of the height and maturity you mention is a waste of time and money. i suspect soil poisoning or something similar. Any road salt runn off?