Approx 3 years ago I planted a row of 13 Leyland Cypress as a screening hedge at the back of my garden (London, UK).
Over the years the trees have been growing well and have approximately doubled in height and greatly increased in density.
However, earlier this spring we had some unusual weather (a very dry, unusually hot early spring, followed by an unusually cold, windy and torrentially rainy late spring).
It was around this time when I noticed the tips of the leaves on the trees going brown. It affected all 13 trees pretty much simultaneously, so I figured it was because of the weather, and made sure to water them more than usual and picked off the dead brown bits (which basically just crumbled off in my hands).
I started researching online and quickly learned about the dreaded seiridium canker. Upon inspecting the trees more closely, I did notice one of the trees was leaking sap, and other trees had some signs of what could be canker, in both the trunk and at least one of the branches (these photos are from different trees).
I contacted the place I bought the trees from, and they didn't seem very concerned about it even when I mentioned canker, and suggested I spray the trees with Neem oil and use Arbrex on any wounds to seal them to deter insects, which I have done.
Now it's summer and the trees are growing fast. The new growth is now all beautiful green and (almost all!) healthy, and the bottom third is now almost completely clear (having picked off the dead growth a few weeks ago, it hasn't come back), but now the leaf browning has spread up the tree and is affecting the old growth on the middle third now.
Here's a photo of the new growth, it looks healthy except for a tiny bit of brown at the end of some of the shoots:
So tell me, good people of the internet -- what am I dealing with here? Weather/winter burn? Insects? Or the dreaded canker.
Please help! 🙏