In general, I don’t have big black knot problem in my yard, found one on plum in past 10 years. But I found two today on different plum trees. Out if curiosities, I cut the branch open to take a look what it did to the wood underneath.
BTW I bleached knife, cutting surface, also soaked the branch and little pieces in bleach before I toss them into garbage.
Here is what it looks like.
I have a single tree that has the worst case of Black knot I’ve ever seen in my life! Unbelievable. I removed a few limbs that had some knots year before last (2019) and didn’t see any last spring. Then last year all the blooms on this tree were killed by frost, so I didn’t spray the tree or pay attention to it last year and its on the far side of my property not near my orchard. Last week I noticed the entire tree is CONSUMED by huge black knot growths all over it. Here is a photo or two…but the entire tree is this consumed. This is an unknown pluot. What is interesting to me is that the tree is in full bloom and aside from the profuse knots it seems completely unaffected! (for now)
Yes, I know this may spread to other trees if I don’t remove it, and yes I am going to. And yes, its probably already too late. The good news is SO FAR I’ve only got 1 other plum tree with black knot…so far! YIKES!
Wow. That is the worst I’ve seen black knot. I agree with you, cut it down and get rid of it!
Yikes… Anyone have a source for Honeysweet or experience if it really is immune or if the other resistant ones like kenmore & president & bluebyrd really are resistant?
OMG, if I didn’t look closely, I would have mistaken them as fruit spurs on a pear tree.
All the black knots I found were in areas of branches rubbing on each other, ie skin were wounded. My yard is small and not have many trees like you do, it is easier for me to spot one in early stage.
Thats it!
Found about a half-dozen knots, cut out same.
Found half dozen knots, cut out same
Kevin,
Your black knot-ridden tree beat out my friend’s tree. I thought his plum tree was bad, yours won hands down 
It is never too late to get rid of it. You know that this black knot was infested since last year and shows it ugliness this year. Getting of it asap, could save some of your trees in the future.
You do spray quite a few fungicides during a growing season. That is probably why others trees are saved.
I had a tree almost that bad… needless to say once I noticed it the tree was in my orchard for about five more minutes.
Knot is like fireblight, some years almost nothing and some years a lot. I only found three knots in my pruning this winter, usually I find a couple dozen.
I thought exactly the same. I actually spray with both Captan AND mycobutanil several times a year AND copper (once a year) so I certainly use a lot of antifungals. But my experience with black knot has been exactly as @scottfsmith put it (and same with firenlight). I’ve had it grow pretty fast on trees I was spraying and in dry years as well as not grow in wet years or when I didn’t spray much. I just can’t find much rhyme or reason to it. Certainly I understand that some trees are resistant and others or not- but other than that I haven’t seen any other factors, including use of multiple fungicides, that seem to stop it on susceptible trees in a given year. Same is even true for being vigilant about removing knots. Sometimes I inspect trees closely and cut it out at first appearance (the whole limb) and other times I get lax and leave knots for a while. I don’t find either way to be a great predictor of whether or not it will spread more or fast on that tree. But I understand I’m going against most literature, its just my own experience and certainly many other factors could be at work.
If all of the branches from the tree are removed can the trunk be top worked?
Daaaymn, and I thought my tree diseases were bad!!!
Most of our club members (MidFEx) in the Midwest have stopped growing plums because of this horrible incurable disease.
Yes, I dont see why not. Pruning recommendations are to cut 4" below wood showing symptoms.
That is too bad. Plum is one of relatively reliable and easy to be taken care of fruit trees in this area. Black knot is controllable/preventable with diligent spray and inspections. If you don’t have black knot in your yard or neighborhood, the chance of getting it is far less than a pear gets fire blight each year.
I have not seen any serious fire blight in my yard after many years. Granted I am careful not to grow or graft blight-prone pear or apple varieties.
Black knot, on the other hand, seems to show and stay (uninvited and unwelcome). Hard to control it except for cutting affected areas of and/or eliminate sources. Black knot is more troublesome than canker, to me.
I don’t doubt that people giving up stone fruit, esp plums, because of it. The thought has crossed my mind.
the chokecherry around my property are infested like that. i found a few small ones on my sour cherry that i cut out yesterday, so i need to spray them as soon as it gets warmer and drier again. neighbor up the street has 2 plums that are infested as well. been trying to convince him to cut them down but he says hes too busy to bother. thankfully hes down wind. 
I took out my Frankenplum with the Methley that was full of it, but this was mainly to try to keep it from spreading to the Euro plums I like better. It didn’t, but I think I have a good chance of keeping it under control. There was one big gall this spring where the bark had been damaged by some varmint.
Well, I have read that many members had mentioned that methley is a black knots magnet. I was attempted but ultimately decided not to graft methley onto my Frankenstein tree. On the picture is the worst looking black knot so far . I have never had black knots developed into a gail. Last time I saw a black knot on my tree that was the year before last. I carved out a section of skin and a bit of the wood in the inflected area. That was it( i do keep eyes out and inspect that branch every time I am in that general area). I do copper spray around buds swell/buds brake in early April every year, not sure this helps control the black knots or not. But this helps control the fireblight on pear and PLC on peach. I agree that areas with bark damaged are more susceptible to be inflected. Both my black knots cases happened in areas that bark had been rubbed by other branches. Since I had pretty bad rabbits damage this year, I added a extra dormant spray of Daconil early this month. Hope this will kill some fugi before I spray my copper. As I said, I don’t have serious black knots problem in my yard. Knock the wood.
