@Graftman,
If the site produces spores, an answer is yes.
The Gall in the picture is not related to the blacknot.
What about the first pic?
In the first picture the black you see is residue from the electrical tape I used to graft. The right side of the graft has what I feel is Black knot.
I also referred to the corky swelling on the right side of the grafting union in the first picture.
I have not seen BK on a grafting union before. I canāt say for sure if it is BK. Some of my grafting unions got swelling growth that looked ugly like that but they were not BK.
All BK on my plums have been on either twigs or scaffolds. It started with that brownish swelling and turned ugly, bumpy black.
Check out this Penn State article. You may find an answer if yours is BK or not.
https://extension.psu.edu/black-knot-of-plum-in-the-home-fruit-planting
I donāt see any black knot in your pictures, but the one out of focus makes it hard to be sure. BK has a bumpy surface like cauliflower or the like, a growth like that.
Then maybe I am overeacting my self. I only found one true blacknot cauliflower bloom this spring which i cut off and treated. Do you think my photos above are what a previously treated blacknot cutout looks the next year? If so I will go down to defcon 3.
Isnāt Black Knot sort of smooth and has an almost velvety surface when it is young? In itās earliest stages it is a single bump and does the coliflower thing as it grows? The pictures on the website links show the rough black galls in their second year.
Iām familiar with graft union compatiblty. I have some pears that have rough ball shaped unions. I donāt think this a compatiblty issue since the galls are only in the scaffold side if the union.
Again thanks for your input. ā¦Iām not trying to be argumentive, just trying to stay ahead of this.
I once had a Methley and let it get totally out of control. Never again.
New growth is green, then it turns tan then black. It always has the cauliflower look to me, but it gets bigger and changes color over time. This time of year the new growth has not started yet and it will all be the black stuff from last year.
Youāve been doing blowtorching for a while now. Is it a time saving option to the tedious business of carving it out of trees? Makes me nervous but I could at least develop surgical technique on my own trees. We spend days carving the stuff out in late winter, spring and summer.
I am not blowtorching black knot yet. It is thick in spots and it would need a lot more heat which could then be too much and girdle a limb.
This reminds me, I need to do my spring check for knots to make sure I got them allā¦ they will soon start sending spores out.
1 Like
So there are no tan knots that overwinter? I currently have tan knots. Are they just regular growth around wounds or branchās that were pruned? I just donāt want to leave anything that could release spores.
I donāt get that, I only have black ones over winter. It sounds like they are not black knot, they are just bark bulges. Knots have that cauliflower-like surface.
I donāt think those are black knot galls at all
Scott, That is encouraging. Where Iām seeing what I thought to be black knot are areas that were pruned, grafted, or had been cut last year to remove galls. Am I correct in thinking this years galls will give off spores? I know they have to be 2nd year to turn black. I just donāt want this to get away. Been there.
The ones from last year will give off spores this spring.
I did a careful check of my orchard and I found three small knots I had missed. No spores from them this spring 
2 Likes
I know this is an older post but wanted to pipe in. I planted a President and a Shiro plum two years ago. They both had black knot a year later and had to cut about 3 branches off. I will say they are planted about 20 feet from a large black cherry. I had previously lost a mature Shiro that was infested with Black Knot and the final straw was a vole girdled the trunk. I had read that they were resistant to Black Knot but now I can say they are not. I have lost many plums to Black knot, but the two large mature plums that have never gotten it are Superior and Alderman. The Alderman is also within 20 ft of the Blackcherry tree and still has never had any BK. The Superior was 10 feet from a Stanley that didnt have a branch without it , and it still doesnt have any. Ive Planted Waneta, Seneca, Bluebird, and Oblinaja and so far no Black knot. The Early Italian I planted got it a year after planting. Since I put in 3 Bluebirds, I like what someone posted about using them as a frankentree to graft to and maybe it will have double the resistance, who knows.
2 Likes
My shiro is badly infected and Iāve seen a spot on my Ozark supreme. Iām going to have to take the shiro out
1 Like
I have cut out two small knots from President. It hasnāt gotten worse, but itās still a little disappointing. I tried the blow torch method on my Rosy Gage, which has it bad on the trunk. Seems to have worked so far. Going forward, Iāll cut out the small easy to get to knots and blow torch anything on a scaffold or trunk.
Each year my black knot gets worse. I cut it out as soon as I find it. I donāt think I have a single J plum or pluot that hasnāt had it. Oddly none of my E plums have gotten it and they are supposed to be the most susceptible. It seems I have a variety of black knot that targets J plums and not E plums.
1 Like