Urgent help getting rid of leafspot/blackspot, holly

Treehelpplease

We have some large mature holly trees in our garden. After the snow in 2018, the holly got winter burn. When this finally seemed to fix itself, early last year it showed signs of leafspot/blackspot. Last summer I bought copper power from a garden centre and sprayed them, as well as cutting off infected leaves, branches and dead branches. I also raked up all dead leaves (there were probably thousands) around the base of the trees and our ash trees. Despite this, it won't seem to go away. Over the last few days, I have cut down some large holly trees that have become completely bare with no signs of returning to life (up to 17ft tall), however this is making the garden quite bare and so I'm afraid to cut down more. I'm not sure if this is connected, but what seems to happen to some of the leaves too is they turn a light green colour, yellow, brown and then fall off. These trees have been there for decades, from before we bought the house back in the '90s (and we were the first owners of the house) so we really don't want to be forced to cut them down. We also don't want the ugliness of the yellow to continue and for the bareness. Does anyone know of any ways to stop the spread of the disease and help the trees that look like they are dying. I feel by next summer it could all be gone Pictures attached

ellee

To be honest that does not look all that bad? You probably just need to keep treating it. If it’s fungal it tends to come back. I had a rose that lost every single leaf to black spot and it just grew new leaves the following year. I’m much more careful to spray early in the season now.

I’m not sure what fungicide you’d use for holly. Maybe the rose one would do the job? I’ve used that on hipcote successfully for rust.

Id be slow to cut down mature trees unless completely certain they were actually dead

Treehelpplease

The ones I cut down were dead - the insides of them were like a plank of wood, they were crumbling when touched and probably would have fallen over by themselves if pushed over. I left around 30cm of the trunk left and a lot had already started to grow new trunks/branches from the root. My fear is these new trunks will face the same fate. It's hard to get a proper picture of the damage as I usually cut the leaves once they're clearly going infected. However, before, the area made up of holly was basically a 6m tall by 8m wide wall of holly. Most of that is gone now, with large gaps throughout and large amounts of empty branches, that have been empty for a year or so

I heard that spreading potash around the base seems to be a good idea, has anyone heard similar?

macraignil

The first photo posted above looks to me more like there is something eating the leaves (maybe caterpillars). I'd be very slow to clear all the leaves from the ground in an area with trees as it is the natural way nutrients go back into the ground for the plants and lots of beneficial wildlife will find shelter there over winter. You might have got rid of the shelter for some of the wild life that was helping control the number of caterpillars. Removing the dead trees sounds like a good idea as there could still be fungi detrimental to the Holly harbored in the dead trees. It would be fairly common to see a touch of disease in the odd leaf but still have an over all healthy tree so I think you might be better just continuing with removing the dead and diseased branches. If the garden is starting to look a bit bare maybe some other plants to fill the gaps should be considered. Cotoneaster has nice red berries in winter and some of the varieties are evergreen. Some other shrubs that are similar to Holly in having prickly leaves but maybe with better flowers would be mahonia and barberry. If you have more variety in what you are growing then disease should be less of a problem.

Treehelpplease

Thankfully, even taller ash trees are next to the holly so during the summer it's fine. And even then, our neighbours behind have tall bushes so privacy isn't an issue, it's more just aesthetics. It's essentially a ditch separating our houses rather than planted trees, so there is still a large amount of untouched area. All the leaves were just moved to another part of the ditch, as well as all the branches I cut down. I agree though that it does look like something is eating it, and I actually heard a discussion about that on the radio today. I'll have to look into something like that, too. I appreciate all your advice and I'm sure I'm probably just over worrying about it. There are new leaves starting to grow, hopefully they will be okay this year