We had a family visit today to nearby(almost next door) farm. I asked few questions about the area pests and diseases as it is a new land for me. He sad, he can’t plant plums. He actually placed an order for them and then talked to somebody from extension and they suggested to cancel the order due to amount of fungus spread by abundance of choke cherries(I suspect he was talking about black knot). I have two Japanese plums in order for spring. Should I cancel it as well? Or it is a way to control black knot on just two trees that would be too labor expensive on a big orchard?
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Two trees should be easy to care for.
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If you’ve successfully grown plums before, I wouldn’t worry about it too much. Black and chokecherry are some of the most common trees in urban and suburban landscapes in our region, so the disease pressure was likely similar at your old place.
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I would say they “grew” OK. Occasional black not, sure, but not killing the tree. My problem was they didn’t produce much. But I guess it was not related to the fungus. But they were European plums, not Japanese.
Galina,
Some Euro plums take a long time to produce. I used to have several varieties. They are more susceptible to black knots than Japanese plums. Black knot showed up on my trees by year 3. It is no fun.
If your area has more chokecherries, your chance is higher. It depends on much much you want to deal with it. Spraying chlorothalonil may help but it has limited use in a season.
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Scott pretty cut the affected areas out and the very black knot-prone varieties got removed. I have a hard time cutting out the black knot infected areas of the branches. I don’t have very sharp knife to do it. I just removed the while limb.
@galinas if you want to grow Euro plums, make sure you choose varieties that will ripen in time for your zone. I have found that varieties I like don’t ripen in time for me like Coe’s Golden Drop, Transparent Gage, etc.
And my trees are in full sun 10+ hours in the summer.
5B is a large area of CO including CSU and CSU recommends some Euros like Green Gage. I have a Stanley and some 4 in 1 Mirabelle on order. I also have Bavay’s Green Gage and Green Gage already. We will see in a few years for me if they can ripen or not in 5b.
Your air is drier and your sun is hotter so we have different climate.
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Nope, I don’t want to grow European plums. Been there, done that, had enough! 
I will try two Japanese. If they will not work out as well, at least I will have the rights to say - I tried!
Galina, if you want Japanese, one of them should be Shiro. It is precocious, productive, cold hardy and a good pollinizer for other varieties.
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True that. Even here we have had mixed problems depending on variety though. My grandma had a plum tree when she had her own house and she claims the plum tree was very brittle and eventually broke in half. I have not experienced brittleness with plum trees but have experienced brittleness with the aztec fuji variety of apple. I got it last fall and it seems to continue breaking all over and a few branches break every time it snows. None of my other apples experience thing characteristic.
hm, I already ordered mine, and it is not Shiro. They are
Beauty Asian Plum × 1
Semi-Dwarf (4’-5’)
Early Golden Asian Plum × 1
Dwarf (4’-5’)
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I don’t know early Golden. My experience with Beauty was not good. Beauty sets fruit prolifically. The fruit was quite large for a plum. You have to thin them hard. Otherwise, the skin that squish against one another often causes rotting.
Also, it often ripens around the time it rains. It turned into a bag of dituted sugar water, After 3 years, I gave up on this variety. I might still have one small graft.
my property is surrounded with chokecherry full of black knot. so far my romance, montmorency and lutowka rose cherries havent been affected. most are in their 6th year and only get sprayed just before full bloom. i did go and chop down every black knot i could find about 3 years ago but im sure there are others ive missed.
will see 
I think tart cherries are not affected, at least no much. I never saw a single one on any tart cherry in my yard. But I saw it on plums.
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put in a black ice plum and contender peach last spring. ill let you know how they do.
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My latest technique is the blowtorch method … it is a lot faster and easier. I just hit the knots until they start to sizzle. You need to be careful to only do one side of a limb and for not too long, otherwise you could girdle it. Also for smaller branches they need to be cut out.
Back on the original topic, the post @Stan mentioned is this one:
But if you go to the thread, the guy I was giving the advice to says he tried removing knots and there were too many so he gave up. He has a wild cherry grove nearby full of knot. So @galinas I’m not sure how you will fare with plums, it depends how bad the knot is there and how diligent you can be on zapping the knots
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