Plums and Pluots without black knot

General Fruit Growing
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I tend to mention problems with my fruit trees and I think doing so is important but I thought it might be a helpful to start a topic which emphasize the ones without black knot or very low occurrences. Even though I’m pushing no/low black Knot all comments are welcome. In my opinion I think mentioning how long you have had the variety is important.

As of now these are the ones without black knot
Odom 3-4 year
Guthrie 3-4 years
AU Cherry Plum 1-2 years
AU Rosa less than 1 year
Spring Satin 3-4 years
Splash 4 years
Maci 4" Seedling 3 years
Tooles Heirloom 1-2 years

Low incidence
AU Producer 4 years
AU Rubrun 4 years Has more incidences than AU Producer

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Black Knot at my location has tended to show up at about three years or longer.

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I never got BK until after 10 years

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The ones I have with high rates of BK are being removed. The ones with low occurrences are on probation.

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At least you had a good run before BK showed up. Now that you have BK are your newer trees getting it sooner?

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I’ve never had black knot in any of my plums/pluots.

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In over 45 years of growing stone fruits, I’ve had only one incident of black knot. This occurred from a graft of President European Plum I received from New York. This happened about five years ago, have not seen any since.

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I planted a Toka and Superior this year after reading up on them and hearing other forum members say that they seem to be resistant to black knot. Also read of Obil’naja and Kaga being pretty resistant. It seems like most of the Japanese/American cultivars are more resistant. I have lots of wild cherries and some plums on my property that have black knot so I won’t plant anything that is susceptible. I might get AU Rubrum and AU Roadside if I decide to buy a few more plum trees.
Here’s a pdf from Auburn University that lists various varieties and compares their resistance to diseases. https://aurora.auburn.edu/bitstream/handle/11200/2083/1297CIRC.pdf?sequence=1

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I cut down the one tree with chronic BK, haven’t seen it elsewhere since, tho I need to keep a close eye on my other older, larger plum. New one is clean.

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Good topic! We tend to just make lists of the bad ones.

Lavina is the only plum I am pretty sure never got a knot in my orchard. It is different genetically than most orchard plums, it has a different growth habit for example.

I have lots of knot, but I just cut it out right when I first see it as I am always carrying a knife and saw. So, I don’t use it as a strong basis on whether to keep something or not. One tree got so many knots at once that I just took it out, but that has only happened once.

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Location might be an important factor,for the presence of Black Knot.Here in Western Washington,I’ve never seen it in the wild and one of my trees bought at a local store,may have some,in one area,that I cut out every year.
jaypeedee’s comment about getting some from a scion,brought up a point.We should be careful,not to spread this stuff around.bb

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3 straight springs of incessant cool and damp have created a nightmare of constant cutting to sustain healthy plum trees here- a good deal depends on site, however, and what aspects create or discourage BK are not all clear. Obviously, good eastern sun exposure is important and not having infected native cherries nearby as well. But I have sites that fill this criteria well that get hammered and other sites without that don’t.

I am not only constantly cutting out BK at most sites where there are plums, I’m also constantly opening up trees to light to try to get the bark exposed to sun as much as possible.

When I started my business over 25 years ago, we tended to have droughty springs and BK was not a problem at all until about 15 years ago. Now it keeps getting worse as springs keep getting wetter.

Of course, I didn’t much enjoy my stingy well during those drier years and hauling around a hose to keep young trees vital, but like a bear coming out of a cave after winter I crave drought as that bear craves warmth and food.

We’ve had a string of over a week of clear beautiful days for the first time in memory. I’ve spent hours and hours cutting out BK in my nursery and orchard. The timing couldn’t have been better.

In my nursery I plant plums where the morning sun first reaches the ground.

So far, it seems as though pluots in general are relatively resistant. I will be curious to see how my Lavina graft does because it is blocked on the eastern side by forest trees.

In the Euro realm, it seems and ACN claims that Bluebyrd is highly resistant. Unfortunately it is also not very vigorous which makes it expensive to use as a mother tree in my nursery, something I’ve been trialing the last 3 years. Any tree not very vigorous is likely to have some resistance and probably reducing nitrogen would be helpful, but then, the vigor helps wounds heal and replace removed wood.

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@TJ_westPA Thanks for the link. This was the list I used initially when choosing my first trees. Later I found this list which shows AU Rubrum susceptible to BK. I don’t understand such a wide rating from 0 to 5. The only two on this list rated zero is AU Rosa and AU Cherry.

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My Satsuma is 5 yearsold, gets only 4 hours of sun. So far, has not had any BK.

My Shiro is 6 years old. I’ve grafted 10+ J plums and pluots varieties on it. Only Shiro that has had BK every year since 2016. Not excessively but it’s there. It gets 6-7 hours of sun, a lot more than Satsuma.

E plums, all 3 are 5 years old. All are in full sun and in an open center shape.

Coe’s Golden Drop has BK last year and this year.
Castleton had it last year. Has not seen BK on it yet this year.
Mirabelle Parfume de September has not had any.

Considering E plums in my yard gets sun from 8 am to sunset and J plums get a lot less sun, my E plums seem more prone to BK than the J ones.

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I have, or have had, an array of some dozen Japanese Hybrids plus a Sapalta chum and American plum, from one to thirty years old (most 2-5 yrs). We’re surrounded by woods and fields full of Wild Black Cherries, a good proportion of which have black knot. I’ve never seen any sign of it in any of my plums (or tart cherries). I’m thankful to say the least. Varieties include: Gracious, Grenville, Kaga, LaCrescent, Underwood, Waneta, South Dakota, Alderman, Pembina, unknowns. Sue

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Wow no black knot. That is one great area. Make my day and tell me you don’t lose plums to late frost or cold weather.

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My yard seems to be full of BK spores from a neglected plum tree in my neighbor’s yard, so this year I got BK on my Dapple Dandy, Flavor King, Flavor Supreme and Flavor Grenade. Splash, Emerald Drop and GeoPride are so far clean, could be mere luck though.

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Hah!! Oh well, can’t have everything. Actually, my biggest problem, I think, is pollination. I’m counting on my american plums doing great things when they start blooming. Sue

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Sue,
If I were bacterium or fungus, I would not want to go to work in zone 3, either :smile:

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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.

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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.

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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. :frowning:

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.

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