Leyland Cypress needle cast

[Ashful]

I have a few Leyland Cypress that are exhibiting signs of needle cast. I have since treated them twice with chlorothalonil, and have been reading up on treatment options (eg. combining a systemic fungicide with the chlorothalonil, application timing, etc.).

All good (well, it sucks), but there is one bit of info I haven't found: long-term prognosis. Once you have needle cast, does it mean I'll be treating them forever, or is there an end to this? Should I avoid planting anymore, despite them having some of the characteristics that really work well for my installation?

In this part of the yard, heavily covered with Walnut trees, I've been planting two or three rows of conifers. The Leylands go in back, where they provide very quick height and privacy, while more moderate growers (mostly Eastern Hemlock) go in front. The Leylands aren't known for a particularly long life (sometimes just 25 years), but they do provide some very fast coverage, while the stronger but slower growers fill in.

Also, I'm finding questionable info on whether I should be treating the slower growers (eg. Hemlocks) adjacent to infected Leylands.

 

[EatenByLimestone]

What's the source of the needle cast? It looks like you think it's a fungus. We've had a really rainy year, causing lots of fungal issues. There's a good chance once you dry out the issue will be under control.

But needle cast can be caused by any stress.

 

[Ashful]

I suspect it could have come from the nursery, as I believe this nursery is not the highest quality (I've had other issues from them), but I can't say for sure. I do fertilize my lawn, and that always increases likelihood for fungus to prosper.

Long-term, this part of the yard will become a thick natural hedgerow, which will eliminate the fertilizer exposure. But I'm just in the early transitional phase of trees in the lawn, now.

 

[EatenByLimestone]

Before putting too much care into them, check your hemlocks for wooly adelgid.