Yellow Conifer

We have three fairly large yellow conifers in our roundabout and my mind has been drawn to them over the last few weeks as they are starting to develop vast areas of brown. We inherited 2 or three dead conifers in borders when we bought the place and I'm worried that these may go the same way. I've identified these trees as "Yellow Holmstrup" (Thuja occidentalis). We've had a dry spell that has lasted for a few weeks but these brown areas have only increased in size since the rains returned. Other sources say that it could be a disease or an insect. I know that Laylandii (the yellow varieties of which can be confused with the yellow holmstrup)get vast brown areas in hedges when pruned. I really hope these things aren't dying as they are slow growing and would take a good number of years to get ones like them. It may only be an annual discolouration - as afterall even evergreens (or everyellows in this case!) need to shed leaves at some point.

Just been doing some more research and it looks like the problem may have been the lack of rains afterall. I've examined the trees and there are no signs of aphid or disease. Conifers are usually very hungry and thirsty trees at the best of times since they have relatively shallow root systems when compared to other types of tree. Also, it can take up to 2 years for the tree to return to it's former glory. Conifers are only alive on the outside - that has immediate contact with sunlight with the centre being almost always dead wood. This more often than not explains the large brown patches in Leylandii hedges, i.e. over pruning or pruning after a long spell of underpruning. Leaves that go brown don't recover so it takes that length of time for good growth to cover it.

Make mental note: During times of drought, water conifers.