Since moving my business from Worcestershire to Christchurch, New Zealand, I've come upon quite a few new challenges. This one has really got me stumped. Portuguese Laurel is really popular here as a hedge or pruned into standards. I'm used to the usual thrip, caterpillar and mealy bug problems with these, but this case has me really stumped. The first one started dying back a couple on months ago and now has only one side alive, the second one is starting to go the same way quite rapidly. They have a pale, almost grey/green appearance on the affected foliage. It seems that entire stems are affected right back to the trunk, with the next stem being fine. They are not overwatered and don't seem to be being eaten by anything. I'm wondering it may be a fungal root disease.
Any advice would be greatly appreciated. Thanks very much.