Thuja Plicante

Hello there,

Lancashire based, planted row of 10x semi-mature Thuja in "full-tree" shape, acting as a screen in April. Manured, fertilised mulched on a mix of clay and new soil. Well drained with french drains adjacent. Plants are increasingly golden / brown on lower branches. Not dead as the lowest branch cuts are still green, but can't seem to stop the dieback. Some suggest aphids (nothing immediately visible), others watering. Rhodedendrons adjacent also somewhat curled. Any thoughts on the problem, and more importantly the solution, before they are lost?

Many thanks

 

If they've been well watered etc, there are other causes it could be.

I did think possibly Cypress aphids and had a quick look to see if I could find more information online.
I came across this rather comprehensive list of possible reasons, have a look and see if any fit the bill.

Thuja Hedge Problems, Pests & Diseases | Hopes Grove Nurseries

 

@AnniD You beat me to it. I was just about to post the same link.
The interesting bit is that it states they've generally gone by the time you notice the damage.

 

Newly planted conifers of that size will need lots of water to enable their roots to establish and support the branches and foliage above. The one in your photo also looks very close to the fence, casting a rain shadow which will reduce the amount of rain reaching the roots. If the trees are also in a sunny location or a wind tunnel, evaporation will be higher, resulting in dehydration and browning of the foliage. Thuja is quite tough though and should recover as winter advances with wetter, cooler conditions.

In the meantime you could increase watering to aid recovery. I have a short hedge of Thuja very close to a fence and it has grown well without extra watering but it is in a sheltered, shady location and the plants were small when planted. Thuja will develop drought tolerance once the plants become well established. The temptation to buy more mature plants to achieve instant screening is understandable but it is unfortunately often problematic as they take more time and effort to establish and thrive.