After 4 years green gage gave fruit ( a decent amount, and it hasnt yet been impacted by plum curcolio thanks to clay spray ) but now I notice a black knot swelling on one of the three main scaffolds, below the fruit set…
All the recommendations say to cut off the branch. Is this really sound advice? Wait mutiple years for fruit, then cut the whole scaffold off and repeat this again in 4 years?…
I will not be doing this. First, I will attempt to excise the swollen ( not yet black ) region, allowing the other side of the branch to continue supply nutrients, and I will not be waiting until winter to do this, so that it cannot heal. I will do it during the next stretch of sunny dry days, and hope that it heals over with healthy tissue during the growing season.
Has anyone had success removing just the area of black knot, and not the entire branch several inches below infection?
Can’t say whether it will be successful yet or knot (sorry) but I did this a little over a year ago on a plum and did not find any new black knot this year. But I think it is too soon to see if it worked but it is looking good thus far
I did take some water based latex paint mixed with copper concentrate and paint over the wounds for some protection of the exposed tissue
Besides surgically removing the infected areas, @scottfsmith has suggested using a blow torch to kill black knot fungus. He has had success with this approach. To burn the infected areas successfully, you will need to practice so you would not burn the infected area too much or too little.
Black knot is difficult to control. That’s a reason why many people gave up on plums.
I hope that doesn’t happen. In the past 6 years that Ive had plum trees planted, Ive only seen a few instances of black knot out of the 20ish plum trees. Each time I cut the branch off immediately, but they were never scaffold branches. This particular one hasn’t matured to the black spore bearing development yet.
If you don’t a preventative spray or get rid of black knot susceptible varieties, you will have more black knot issue as your plums mature.
Tye problem is no one spray is known to be effective. Chlorothalonil is recommended in early growing season before fruit set as it has a long pre harvest interval.
You should put your location in your profile. I don’t know where you live. In the east coast, you can’t avoid black knot.
Unfortunately there does not seem to be many resistant varieties? I like European plums the best (and prefer the larger varieties). On the small list of somewhat resistant varieties (that I could find), one of my trees (Methley) is listed, and that tree has had the most black knot of all my trees… ( I also do not like the plums. They taste good but are small and too watery; there is no firm meat) I have girdled that tree, producing new scaffold, and re-grafted it all with Hollywood plum. In a couple of years I will remove all of the Methley scaffold, and keep the new a proper manageable height and shape (never pruned it appropriately to begin with).
Today I cut the black knot off. I only removed the knot itself, and a very small perimeter. There didn’t appear any discolored tissue beyond the region of the knot itself. I then coated the wound and surrounding with copper solution and wrapped it with grafting tape. I will update on this later in the year.
Side note: Sadly, two PC are no longer with us today.
From all of my reading here, my impression was that Methley was highly susceptible to black knot, if that makes you feel any better about its condition.
I have a couple Italian plums near tons of chokecherry bushes that all have black knot. Am I just wasting my time? The plums have been there for a couple years now and haven’t gotten it yet. I figured maybe they were more resistant than the chokecherry.
I do not know where the originating black knots are near my trees, perhaps in some old wild cherries but I cannot see any around. Without any in sight, my trees are still getting it, but not very much so far.
If you have lots of black knot visibly nearby, in all likely hood your plums trees will be ( and are already ) infected. It takes a couple of years before the infection is very evident.
Black knot is rampant here, thanks to a huge population of wild black cherries that serve as a reservoir.
After tons of research, I’ve given up trying to grow sweet cherries, Asian plums, and most European plums. But I have had some success growing the European varieties Bluebyrd and President, disease-free. I am adding Empress. Bluebyrd has fruited. The crop is late but delicious.
I’m also trying out some American hybrids. Alderman has grown here for many years without disease; my only problem is finding a good pollinator. I had Black Ice but it developed both black knot and blossom rot. I’m adding LaCrescent and Toka, searching for a disease-free pollinator. Fruit wold be a bonus.
So based on what I have seen, Bluebyrd and Alderman seem immune; President is at least highly resistant.
That’s what I’ve been expecting. There’s no chance they haven’t been exposed. The last couple years here have been super dry, which may have helped slow things. I’m just hoping I can stay on top of it. My climate is pretty dry, especially in July through September.
Now that I think about it, there have been two sweet cherries in the yard, and a flowering cherry, for about 8 years prior to the plums ( same vicinity) and neither have ever gotten black knot. They must be a resistant variety? (not sure which, no one cared to save that info when planting… )
I have no idea. Some tree, like wild black cherries, are tolerant – they carry the disease but don’t necessarily;y die from it. Maybe these trees are tolerant. I’m no expert, but I’m not aware that there are tolerant / resistant sweet cherries. Sour (pie) cherries are supposedly resistant.
My plum (1/2 italian prune, 1/2 Toka) bloomed as usual this spring but the non-Toka part seems to be dying. All branches have turned brown and leaves fallen. Toka is actually grafted up above the prune parts and those branches look green and good so far.
Darn thing has been suckering like crazy. I almost regret planting this more than goji berries (yuck)
Im hoping to let the toka branches harden their growth a little and graft/bud a sucker before taking the whole tree down.
Or is the sucker likely to succumb to the same thing?