Chokecherry Black Knot

Discussion in 'Fruit and Nut Trees' started by Bob Dunn, Aug 14, 2020.

  1. Bob Dunn

    Bob Dunn Active Member

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    5A4178F4-B6C7-41E6-87F0-1F2CCEDBDF9E.jpeg 7A5ED158-9E27-4BE4-908A-2A20B8DC4528.jpeg Good day,
    My chokecherry occasionally gets a branch with black knot. I cut these off far back from the disease. This year, I notice significant splits in the central trunk bark, but no clear-cut evidence of black knot in the splits (except for the one photo from high up in the tree). Is this part of the disease? Should I cut it out wherever it occurs?
     
  2. Acerholic

    Acerholic Esteemed Contributor Forums Moderator VCBF Cherry Scout Maple Society

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    @Bob Dunn, good evening Bob, to start with all the infected wood should be pruned back in the Autum and next Spring the tree should be sprayed with a fungacide. As far as the spitting in the bark is concerned IMO this is from environmental reasons. Bark splitting can occur in response to various environmental factors at different times of the year. Splits can occur on the trunk of the tree as well as on branches. Trees that are most susceptible to this type of injury are those with thin bark, such as certain fruit trees. Newly planted trees or young trees are more prone to bark splitting. Bark splits are not likely to be fatal to trees, although they will, in some cases, allow entry of disease organisms, which can cause decay.
    I am not saying your Chokecherry can be saved, as it does look particularly well infected , but it never hurts to try.
     
  3. vitog

    vitog Rising Contributor 10 Years

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    The first photo shows what appears to be a large branch badly infected with Black Knot; it should definitely be removed.
     
  4. Bob Dunn

    Bob Dunn Active Member

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    Thanks. I’ve removed one more affected branch. I have a sulphur-based fungicide in powder form. What’s the best way to apply it? Does every leaf need contact, dust, mix with water, etc.
    Bob
     
  5. Acerholic

    Acerholic Esteemed Contributor Forums Moderator VCBF Cherry Scout Maple Society

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    @Bob Dunn, tbh Bob, I really don't think the fungacide will do much good at this time of the year. Next Spring is the time for spraying IMO.
    Regarding mixture I apply 3 tbsp of Sulfer per gallon of water. I place this in a spray bottle and cover 'all' leaf surfaces.
    I have attached a photo of the sprayer I use.
    You must be ruthless and remove everything that is infected and preferably burn.
     

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  6. vitog

    vitog Rising Contributor 10 Years

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    I don't think that there is any effective treatment for Black Knot other than removing the affected parts. A lime-sulfur dormant spray may help to prevent it. The only spray that I use on my plum tree is a late summer copper spray for controlling Coryneum Blight, which seems to only affect the Japanese plums on the tree. The Italian Prune part of the tree is not bothered by the blight but seems to be more prone to occasional Black Knot.
     
  7. sgbotsford

    sgbotsford Active Member 10 Years

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    Black knot spreads during the growing season by spores. It enters the tree through any open wound, including a leaf that is torn off.

    For obvious reasons, don't remove black knot during the growing season.

    The mycelium spreads through the wood of the tree. I think you can see it as a stain in the wood. Experiment by cutting near the visible knot, and cutting progressively toward the trunk.

    Mycelium cells on your pruner can transfer to the next cut. You need to sterilize your pruners between cuts. Bleach diluted 10:1 works for this, but it takes about 30 seconds to be effective. If you go this way, you could use two pruners, and alternate which one is in the bleach bath. Note that bleach is corrosive and will pit your pruners. May want to buy cheap pruners for this.

    Disinfectants that deal with spores, don't destroy your tools, and aren't hazardous to be around?

    It's a lot easier if just dealing with embedded mycelium.

    * Do spores scatter if you prune during the dormant season?

    * Can they get established during the dormant season, or remain on the wound until warm temps return?
     
  8. Ron B

    Ron B Paragon of Plants 10 Years

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