all the leaves are brown...

That's sad :o(

I'm a bit worried that it'll turn out to be one of those horrid diseases that are effected the rhododendrons a few miles away in the Clyne valley. Phythophora kernoviae was the one causing trouble there, and there's another called phythophora ramormum. I've been looking at all the pictures I could find on the internet, and none of the leaves shown there have got the crusty white bits underneath, which I am still hoping will turn out to be immature scale insects.

We sprayed with a systemic insect spray and it killed the scale mites we had on our twisted hazel tree.If you use the bay leaves from your bay tree for cooking with, you would have to look on the bottle first before using it on edible produce.

Thanks Lindak. I found some organic bug spray that claims it kills scale insects and is suitable for use on food crops. Used it a couple of times and haven't seen any further signs of scale insects.

The really good news is that since I pruned out all the dead bits there have been no signs of it coming back. I've been keeping an eye on the bushes and am nursing a tender hope that perhaps the damage was nothing more sinister than the result of the unusually frosty winds this winter. Fingers crossed.

I'm glad that the spray ended with a good result for you. You can usually see scale insects quite well as they attached themselves along the woody stems etc. They look like very tiny limpets. If you have frosts for a while leaves can turn brown especially if the plant is on the tender side. OUr neighbour planted a rose bush that was sprouting and the frost caught the first lots of young shoots and he was worried about it but I told him that it would be o.k and it is going away fine now although it did lose the leaves as they all went brown.