Clematis problem

Hi livvielou, well, with no image to help diagnose it is difficult to be sure even with your very good description of the problem. I have around 182 Clematis scattered around the garden and they only rarely get visited by Clematis Wilt. One of the problems this year has been the warm, wet, moist weather which can cause attacks of several kinds of fungal disease but the best way to attempt to cure the problem is to treat it like a case of Clematis Wilt.

Below are images of Clematis Wilt but, to be honest, it can be difficult to id from other fungal diseases as most will affect the plant right down to the ground.




So I would advise that you cut the Clematis down to the ground now, sprinkle some soil or compost on the site, just enough to cover the cut back stems. Clematis Wilt does not always proved fatal to a Clematis although I have had cases where a plant has not recovered but, mostly, my Clematis grew back just fine after the pruning.
One good thing, since your Clematis is over 20 years old, it's well established and being a Montana is also a strong, robust grower so using the standard treatment for Clematis Wilt, for which there is no cure, of pruning the Clematis right to the ground will induce it in a couple of weeks to show new growth poking out of the soil. When that happens give it a feed of general fertiliser or Tomato Feed.
Let us all know how you get on with the plant.

 

Hi, well, from what I can see from your images it is not Clematis Wilt as apart from discolouration of the leaves they are not wilting and I would not prune it at present. I would, for the moment, give it a weekly feed of, say, Tomato Feed to help the Clematis recover over the next three weeks or so. But, should the Clematis not recover or get worse, (although I think it will recover), then I would advise that you cut the Clematis to the ground as you would for Clematis Wilt.
Let us all know how the plant gets on.

 

Hi livvielou, well, I do see one problem with the Clematis, but it does look like the plant has coped with it, and that is it is planted very close to the brick wall putting
it in the rain shadow where it can be dry and, of course, Clematis like their roots damp and cool.

Thanks for that last image as it helps greatly. I have a Clematis Armandii which has a similar size trunk and age, but is an evergreen variety, and is near enough immune to Fungal Disease but, should it get attacked, I would not cut such a thick trunk to the ground, instead I would cut it back to the first three outgrowing stems and then cut those stems back to the first joint and I would keep the roots watered, but not over soaked, and still give it a weekly feed.
Although leaf drop is, visually, very distressing, it can be usually be cured over time with feeding and watering. The leaves are not withered, twisted or curled to any great extent which is why I do not think the spray you mentioned is responsible. What I do think is responsible is the warm, wet, moist weather we have had and that will encourage fungal disease causing leaf drop. Give it time and cross your fingers, which is how most gardeners do when a favoured plant is showing distress. Again, let us know how you get on.