Hi folks. I have a plum tree that developed black knot a year or two ago. (At least I think that's what it is.) The advice I saw at the time was "cut out the infected areas, leave it be for a year to heal." I did that, and this year the infection is back. It's on some lower down branches, some very high branches that are hard to get to (it's an old tree), and a few growths on the larger trunk lines.
I fear if I just keep hacking bits off of it, I won't have much of a tree left (plus it's a few hours up a ladder trying to not fall off). Is there a good way to get rid of it for good that will still leave me a tree, or is it time for a tree funeral? (I hope the former.)
Crell, welcome to the forum. It's great to see first posts from new contributors.
Many of us are in the Pacific Northwest in an area where black knot isn't really a threat, so don't have much experience with it. I'm a little familiar with it because I had a brief infection from some scion wood that was sent to me in the mail.
From what I've read, see link above, if you aren't able to remove all of the visible knots, and stay on it, then it sounds like a lost cause. You can use fungicides, but they will only help prevent new knots, it won't address the ones that are already there.
The suggestion is to plant a resistant variety. If it were mine, before I got rid of the whole tree, I'd probably cut it at ankle height, and bark graft a resistant variety to the stump. Or wait until early spring and cut it flush to the ground. If its on a rootstock, it will send up suckers - which are hopefully knot resistant - and you can graft to those later with scions wood of resistant varieties.
Sorry I don't have better news.
Another method you can use in addition to the other techniques is to use fungal compost tea.