This thread is well timed. I spent several hours earlier this afternoon going around and cutting out black knot. In the past, I had a bit here and there, but it got pretty bad 3 years ago and has gotten progressively worse. I cut out everything I saw when dormant, though it is easy to miss some. So I was surprised to see the sheer scope of the issue.
Some of the trees had significant portions like this pic- enough that I just cut off 1-2" diameter sections of the tree.
I was just remarking on how little knot mine had. I think it had some, though it is possible that it was a graft of something else which had it.
The plums at the bottom of the yard are the worst hit. Not only does the area stay moister, they also lose out on some afternoon sun from the neighbor’s trees.
Of the 4 Asian plums down there:
- one AU (Rosa or Producer) died over the winter and the other had a lot of black knot
- Laroda- lot’s of black knot and not much set
- Lavina- little (possibly none) black knot. It also had a reasonable fruit set.
- Purple Heart (a graft on Laroda from wood Scott sent me in 2015)- some knot, but not so bad. Also has good fruit set. This one branch is had 90% of the fruit from the tree. Of course, after I was done cutting away the Laroda’s black knot, the Purple Heart branch was half of the remaining tree…
Here’s a pic of the Purple Heart branch. Note the single knot removed near the bottom of the picture.
I have my pluots in a prime sun location, yet they still get their share of black knot. I must have very high pressure at my site. Of course, I put 2 pluots in at a rental a couple years ago (I know, not a good idea, but I had a lot to plant and was looking for a spot for them). It’s about a mile away and was almost immediately infected. When I was over there today mowing, I pruned out a lot of knots from both.
The neighbors up the hill from me have a large native cherry which is probably a constant source of inoculation. It is at the top of a 8’ tall retaining wall, so it is an ideal location to rain down spores on my entire yard. The actual owners are the parents of the wife and her mother has a soft spot for the tree, which has kept them from removing it so far, even though the couple living there don’t like it. But it looks like they may be ready to do it this summer. I’ll rejoice, not just to remove the inoculate, but to get more morning sun to a good chunk of my yard.
In terms of Euros, I don’t think that I have any which haven’t gotten any knot. Middleburg is supposed to be very resistant, but it still got a decent amount. It wasn’t one of the bad ones though. Bluebyrd died on me (snapped off at the graft union), so I don’t really have a datapoint there.
Earlier this afternoon, I cut ~10 knots off a relatively small Satsuma, which gets a lot more than 4 hours sun (probably 8-10). It was one I planted in a fabric pot back in 2012, then planted the pot into the ground in 2013, so it never got all that big. But it seems to get strikes near the tips, so I didn’t have to cut out much of the tree
I was cutting it out of Geo Pride as well.
I think part of my issue is that I try to save too much of the tree. It is tough when the knot is either on the trunk or a major branch. I try to cut it off, but often see re-growth around the edges.