Scott's blowtorch method for black knot

Here’s a topic that came up elsewhere that more folks would probably like to read about!

@disc4tw @alan @WildApple23


with all the cherry i have put in, i know someday ill find b.k in them even if i spray. good to have this knowledge in my arsenal as well.


I don’t have this problem yet as I haven’t played much with plums so far, but for clarity’s sake:
For “blowtorching knots on larger branches” are we burning out small spots (like freezing out a wart) or is it a matter of raising the temperature enough to kill off a disease but not close enough or long enough to do an actual burn?


I ended up buying a blowtorch because of this. Thank you for the tip!!

I can see the merit in this, although I would like to hear clarification on blowtorching (@Mtncj 's question covers what I’m wondering). I’ll also say that I think my black knot issue is worse than @scottfsmith 's , I would get 5-10 black knot growths on my single plum tree every year, and the tree was about 3 feet high before I cut it down. It might still work if I decide to try again though.

Thanks for the link @Richard

It’s more the latter. If you see smoke you are probably burning more than you need to. That said, on large cankers on a large trunk I may take it all the way to smoke to make sure I nailed it.

Oh if its a canker they trend to “drip down” into lower bark so make sure to do it quite a ways down. I learned this from when I was cutting them out. Note for both canker and knot it is good to cut some out just to understand how far they are spreading. After cutting out you can torch to make sure you got it all.


@scottfsmith ,

This torching technique is worth an educational video! Perhaps you can do one this year.


So I have a young plum here with a gall… Same as black knot right?

The tree is very small caliper as it was a whip when planted this spring.

When you torch it, do you mechanically remove any part of the gall first? The knot is so much larger than the trunk of the young tree, I’m worried about doing damage to the trunk.

Also when do you stop hearing it?

Te me,it’s sort of like surgery.How much can be taken off,without seriously damaging or killing the whole thing?

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Because the caliper of the trunk is small, I would need to be careful to avoid damaging the trunk…

I’m thinking a dremel tool, then torch.

But I will wait for other opinions. It’s a small tree but I can simply replace it in spring though I’d lose a year.

It’s part of a 5 plum espalier I was starting. Only 2 of the whips broke dormancy after planting. The other 3 died.

They came from Tyty. Unfortunately they seem to be the only company selling such small whips for something like $18.95/ea. I’m grafting 3 new trees to replace the 3 dead ones onto Julien A I have ready…but I don’t have a 4th rootstock for this one, so I’d like to save it.