Beware of Black Knot Disease on Cherry, Chokecherry, and Plum Trees

Updated on November 16, 2016

Black Knot Disease

(Apiosporina morbosa)

The problem with black knot disease is that it's hard to detect. My tree was infected with this fungus two years before I saw any sign of the problem. The fungus grows under the bark and is invisible until the branches begin to swell. Rain spreads the spores.

I thought beetles were the problem, but I was wrong.
I thought beetles were the problem, but I was wrong. | Source

What to Do to Treat Black Knot Disease

  1. Check your tree each spring.
  2. If you find rough swollen branches, cut them off.
  3. If you find black gulls growing, you are in big trouble. These must be cut back at least six inches beyond the healthy part of the branch.
  4. Every single branch with these gulls must be cut—you can show no mercy.
  5. The cut branches must be removed and disposed of in such a way the spores cannot escape into the air or be exposed to rain. If you leave them for curb pick up, you might want to label the bag. It is probably not a good idea to burn them, but you could cut them up and bury them.

Look for branches that are rough and swollen.
Look for branches that are rough and swollen. | Source
This was taken last spring when the damage was not so obvious.  Had I known what it was and what to do, I could have avoided the worst stage.
This was taken last spring when the damage was not so obvious. Had I known what it was and what to do, I could have avoided the worst stage.
Black gulls need to be cut out -- I did not realize the importance of removing ALL the gulls.
Black gulls need to be cut out -- I did not realize the importance of removing ALL the gulls. | Source
Swollen stems are hard to see: look closely.
Swollen stems are hard to see: look closely. | Source
You can see the swollen stems if you look closely.
You can see the swollen stems if you look closely. | Source
This and the following pictures were taken the next spring.
This and the following pictures were taken the next spring. | Source
The whole entire tree was over taken by black gulls.
The whole entire tree was over taken by black gulls. | Source
The only thing to be done is to cut these branches away and discard them very carefully.
The only thing to be done is to cut these branches away and discard them very carefully. | Source
Source
In the end, a white mold grows on this fungus and sadly your tree is disfigured  and weakened.
In the end, a white mold grows on this fungus and sadly your tree is disfigured and weakened.
I had to cut the tree back really hard as the damage was so bad.
I had to cut the tree back really hard as the damage was so bad. | Source
New hope after cutting the tree branches back really hard, I hope the tree recovers.
New hope after cutting the tree branches back really hard, I hope the tree recovers. | Source
Lots of new branches -- looks like it will make it -- not as graceful, but it will survive.
Lots of new branches -- looks like it will make it -- not as graceful, but it will survive.
I will post updated pictures as the tree grows.
I will post updated pictures as the tree grows.
The tree is still growing and looking healthy.
The tree is still growing and looking healthy. | Source
Source
September -- the single branches are developing branches.
September -- the single branches are developing branches. | Source
June 2013: the tree was fully restored and much bigger than when I first trimmed it.
June 2013: the tree was fully restored and much bigger than when I first trimmed it. | Source

Questions & Answers

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      • daughterson profile image
        Author

        Faye Mitchell 3 years ago from Columbus, Ohio

        I am not sure burning is a good idea -- it may spread the spores.

      • profile image

        JD 3 years ago

        My Japanese plum tree and 2 cherry trees are infected with this. I just cut them all back severely before the snows started melting here in Maine. Is there any chemical spray that I should use in conjunction with cutting? I saw no info on that.. Also, I plan on burning branches I cut as soon as the snow melts - is that OK? Burning won't spread the spores will it? Thank you for posting all of the information!

      • daughterson profile image
        Author

        Faye Mitchell 3 years ago from Columbus, Ohio

        I don't know.

      • profile image

        Cc 3 years ago

        I too am wondering if it is safe to eat the fruit from a tree infected with black knot?

      • profile image

        Vicky 3 years ago

        I am also concerned about eating the fruit from my infected plum tree. Are they still edible?

      • profile image

        Jen 3 years ago

        Is it safe to eat the plums if the tree has black knot.

      • profile image

        Wendy 4 years ago

        I have just cut off all the infected branches on my chokecherry trees and found orange speckles on some . Does anyone have any idea what it might be and how I can deal with it ? Is there anything we can spray our trees with to help curb the problem ?

      • daughterson profile image
        Author

        Faye Mitchell 4 years ago from Columbus, Ohio

        Thank you Dennis Rose for your comments. You can bury them - deep. Don't burn them. You want to keep the spores from spreading.

        Answer from past comment:

        Hi Julie, that is a really good question. I would put it them in bags and lable them or bury them far away from the trees, or call the local yard waste pick up, and ask them. You could lable the bags so the yard waste company knew this needed to be dealt with in a safe manner. The desease spreads by water splashing on the infected branches so I would think burying them would be a good option. As for buring I don't know enough to say that would destroy the spores. Burying them would keep the spores from getting into the air. These spores only affect certain trees. Let me know what you decided.

      • profile image

        DENNIS DE ROSE 4 years ago

        My tree has had the disease for 2 years. I did some pruning last year but obviously I did not get it all. This year, now Aug 4th, I am aggressively trying to remove all infected branches. There is some growth at the base of the tree that seems to be unaffected. I have had the tree for quite some time, perhaps 20 years or so. I noticed the infection only after the tree was severely damaged when one huge limb was accidentally split. A friend was climbing in the tree to harvest the plums. My only question now concerns disposal of infected limbs. I cannot find any info about that? Has anyone had any luck with that? Thanks. The pictures here helped me quite a bit...Dennis

      • daughterson profile image
        Author

        Faye Mitchell 5 years ago from Columbus, Ohio

        It is a very pretty tree but you are right it is susceptible so I guess one just make the that choice. after cutting my tree back in the extreme it is now healthy. Make your own decision.

      • profile image

        Rick Morganberg 5 years ago

        DON'T BUY THIS TREE. IT'S GUARANTEED TO GET BLACK KNOT. IT JUST ISN'T WORTH IT.

      • daughterson profile image
        Author

        Faye Mitchell 5 years ago from Columbus, Ohio

        I think you could wait a month, but keep a close eye on it. Good luck with your tree. As for the other trees they have already been exposed.

      • profile image

        bdjlamb@hotmail.com 5 years ago

        I just noticed this disease on our one chokecherry tree and am very disappointed b/c it provides incredible privacy. It is b/w our neighbours deck and ours and is very large. Your photos and info are so comprehensive, I realize I'll have to pretty much cut it down to nothing as so many branches are infected, removing our privacy. Can I wait another month until summer is almost over or will that be foolish

        and encourage spreading to nearby trees?

        dj

      • daughterson profile image
        Author

        Faye Mitchell 6 years ago from Columbus, Ohio

        The sooner the better. Your tree will only get worse. You can wait until the fall but that will only give gulls more time to develop. I cut my tree back so hard I thought it would not survive but it did. It is a terrible desease. Good luck. You have to cut out every single gull.

      • profile image

        DENISE 6 years ago

        I need advise my plum tree is loaded with black knot almost every limb does anyone know if its to late now to prune

      • daughterson profile image
        Author

        Faye Mitchell 6 years ago from Columbus, Ohio

        Hi Julie, I know how awful that is. My tree was eaten alive by beetles that is why I did not see the real danger. If your tree has black knot desease you must cut every single branch that is affected. As for the beetles I don't know. After pruning my tree recovered and was not attacked by beetles. Wet weather does not help -- try calling a tree surgeon or a local university that is involved in agriculture.

      • daughterson profile image
        Author

        Faye Mitchell 6 years ago from Columbus, Ohio

        Hi Julie, that is a really good question. I would put it them in bags and lable them or bury them far away from the trees, or call the local yard waste pick up, and ask them. You could lable the bags so the yard waste company knew this needed to be dealt with in a safe manner. The desease spreads by water splashing on the infected branches so I would think burying them would be a good option. As for buring I don't know enough to say that would destroy the spores. Burying them would keep the spores from getting into the air. These spores only affect certain trees. Let me know what you decided.

      • profile image

        Julie 6 years ago

        When disposing of the cut branches, do we burn them? It seems that putting them to the curb for pick up or burying would just spred the disease. How do people who are not allowed to burn, deal with it?

      • profile image

        Julie 6 years ago

        My plum had the beetles so bad last year, we were litterly taking them off by the handfulls to dump in soay water. The tree was covered in young fruit, but by the end of the season, not one was salvagable. Everything was shriveled and moldy. It was heartbreaking to watch it all slowly rot and die. I was going to give in and spray this year, but before the bud it was so cold and wet that there wasn't really any day to do it . Now the flowers are out. Is there still time to help it for this year? What can I do? It is terrible to have to watch the slow torcher of a tree trying so hard to survive.

      • profile image

        Millie 6 years ago

        I also have a plum tree that I have been pruning regularly so I don't have a lot of knots. There has to be some kind of fungicide that will help control it. I used a powder form some years back and it kept the knots away for several years. Can't remember what I used. Does anyone have any idea?

      • daughterson profile image
        Author

        Faye Mitchell 6 years ago from Columbus, Ohio

        I am not a tree expert, but I think it will be alright. I cut mine back in the autumn, and it was fine -- the problem is that I didn't cut it back enough so in the spring the infected branches spread. It is important to get every single branch that is affected. Good luck with your tree.

      • profile image

        Donna Gregory 6 years ago

        I started cutting mine back now in October. Is that okay? I won't hurt the tree, will I?

      • daughterson profile image
        Author

        Faye Mitchell 6 years ago from Columbus, Ohio

        In the spring as early as possible you must cut it back and it will be worse in the spring than it is now. Good luck!

      • profile image

        Val 6 years ago

        I live in Alberta. Is it too late in the season to cut off all the black knot? My tree is 20 years old?

      • daughterson profile image
        Author

        Faye Mitchell 7 years ago from Columbus, Ohio

        The sooner the better, the gulls will only get worse. I know it is painful. When I cut my tree back I was afraid I had killed it. Good luck. I don't know about summer heat -- just the gulls, gulls are probably worse than heat.

      • profile image

        larry 7 years ago

        Sadly my tree is infected BAD...Its June 12..Should I prune the heck out it now ? ..Will the summer heat kill the tree ? My wife is very upset.

      • profile image

        jarvis 7 years ago

        Thank you sooo much for posting your article! We noticed the black knots this year and had no idea what was going on. We hate that we have to cut so many branches because they are beautiful trees. Do you know what causes this disease or how we can prevent it from happening again?

      • daughterson profile image
        Author

        Faye Mitchell 7 years ago from Columbus, Ohio

        Thank you -- I look forward to seeing your tree recover.

      • profile image

        dorothy 7 years ago

        My plum tree looks bald, like the newly recruited marine! But at least, I got rid of those ugly black knots. Thank you. Will keep you abreast of developments, if any. Cheers!

      • profile image

        Daughterson 7 years ago

        Good luck Dorothy -- show no mercy on infected branches. They must go. I hope your tree recovers as did mine, but you must cut them all off -- all of them.

      • profile image

        Dorothy 7 years ago

        Thank you for writing about this problem, because after reading and seeing pictures of your plum tree, I am going out today to cut back all the branches cause the whole tree is infected with this disease.

      • daughterson profile image
        Author

        Faye Mitchell 7 years ago from Columbus, Ohio

        That is a very good point IN2Deep. I never thought of cleaning the tools -- probably because I only had on cheery tree.

      • IN2Deep profile image

        IN2Deep 7 years ago

        This happened to both my plum and cherry tree-I did the same-it looks much better now.It is really important to clean-wipe your pruning tools so you do not spread disease,fungus ect

      • daughterson profile image
        Author

        Faye Mitchell 7 years ago from Columbus, Ohio

        Before my tree got infected the trunk and branches were so graceful and beautiful, but it has never had fruit. I am amazed how much it has grown this year. It isn't so beautiful but it did recover.

        The sad thing is that no-matter-what you have to remove each and every infected branch and then remove the waste and rake up all leaves stems.

        My tree recovered in one season but if it bore fruit it would not bare fruit until the next season because I cut all the branches off, but if you have some branches left I really don't know.

        Also I would think it would depend on how many branches you have to remove. It is sad, a beautiful old and graceful tree cannot be replaced, and neither can the fruit.

        It is worth a try -- the pictures above of the recovery are from just this year and it has grown really well. I am adding a new picture today to show how much it has grown this summer. Today is September 1, 2010 -- I cut it back in March 2010.

        I am not an expert -- but this is what I have experienced.

        Good luck with your tree. Let me know how it goes.

      • profile image

        Patricia L 7 years ago

        My tree has the same problem - it's a much bigger tree though, probably 25+ years old with a lot of character. I want to try to save it. Has your tree had fruit since you've cut it back? How long did it take to see the new growth? (One or more seasons?)

      • daughterson profile image
        Author

        Faye Mitchell 7 years ago from Columbus, Ohio

        It my understanding that it only affects the trees mentioned above. None of my other trees were affected.

      • profile image

        Tommaso Petrella 7 years ago

        Does this problem occur only on certain select species or can this effect any and every tree if left unattended?

        Thanks!

        Tommaso

      • daughterson profile image
        Author

        Faye Mitchell 7 years ago from Columbus, Ohio

        You are so welcome edith. I was so upset by my tree that I hoped I could help others not make the same mistake I did. I should have cut off all the branches not just the worst. Good luck with your tree.

      • profile image

        edith 7 years ago

        While I was looking after my seriously ill husband, the black knot on our damson plum went unattended for a couple of years. Today, I cut off most of the infected branches, very similar to the photo that you show above. Hoping to find some more information about possibly being able to save the tree, I went back on the internet and found this site. Your article and the wonderful and very informative photos have given me hope. Thank you very much for sharing.

      • daughterson profile image
        Author

        Faye Mitchell 8 years ago from Columbus, Ohio

        Thank you lisadpreston.

      • lisadpreston profile image

        lisadpreston 8 years ago from Columbus, Ohio

        Beautiful pics. My favorite tree.

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