Where did you read that E plums are more susceptible? I’ve never read that anywhere and it certainly hasn’t been my experience in the last 30 years of growing plums outside of NYC in orchards on estates. I do manage one J type that is a hybrid from a Cornell breeding project Cummmins sold me that doesn’t get black knot, but the big and beautiful plums lack adequate sugar. I should probably start using it as interstem. Only Blue Bird of E. plums I grow seems immune to black knot but they don’t tend to get it as bad as the J’s. The more vigorous the tree the more susceptible seems to be almost a hard rule.
All my plums, Euro and Japanese have gotten black knot.
E plums have gotten it worse despite being open center and in full sun. J plum (multi grafted tree), was in partial shade and took a year or two longer to get it.
I think @scottfsmith has mentioned in the past that J plum is less susceptible to black knot than E plums.
Alan, I thought I read that on this form over the years. I hope I’m wrong. I have a multi graft 15 year old E plum that has fruited for the first time this year. I also have two others about five years old that haven’t fruited. I sure don’t want to fight it with them or worse yet loose them.
I will say that, to my knowledge, I have more experience with more trees and more sites than anyone else on this forum, probably at least 50X more, but it is nevertheless limited to the regions within 2 hrs of my location, about 50 minutes N. of Manhattan. In different zones and relative humidity there may be different results. I know the results here can be much different in sites very close to each other with no apparent explanation, such as eastern shade at one and not the other. It does seem that being in a hollow without exposure to wind and where dew remains on the trees longer does make the chances of problems greater, as well as eastern shade, but results are inconsistent. However, I haven’s seen a single site where the E’s have been more susceptible than the J’s.
We have been in a pattern of very WET springs and until this year very wet summers and I believe that has multiplied disease pressure each subsequent wet spring. It is becoming too expensive for me to make a profit on my Euro plums in my nursery because of the high cost of repeatedly cutting out black knot. Because they grow faster and are ready to sell at least 2 years sooner as decent sized trees, J. plums are still making me money.
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I agree things are regional to a degree. I am a bee keeper and with them it’s very true.
Do you know of any E plums to stay away from?
I currently have Stanley, Imperial Epineuse, and Rien Claus Bevay fruiting. I can pass on the Stanley, nothing special there.
Not yet fruiting is Vision,Valor, Middleburg, and Perfume de September. Is there anything you would recommend?
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Blue Byrd is a prune plum of high quality that seems to be completely immune or highly resistant. Adams County Nursery claims as much and they are a source of it, but the trees they have of it are tiny and take a long time to plug in for me. I gave up on using them in my nursery for that reason, but I might start using grafts to change over trees scaffold by scaffold, since the majority of the galls form on branches- that’s what sucks up most of the time. If two of 3 scaffolds were Blue Byrd there’d be a lot less time spent cutting out galls.
Stanley is a very reliable cropper here and any tree ripened plum is pretty good- but Castleton fills that bill with a better tasting plum. I just wish it was more vigorous.
The american plum seems resistant to everything. Some of these wild plums i chose to keep are bigger, delicious , and totally disease free. They are not insect free.
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I know for sure where I am Mirabelle Parfume de September has the worst black knot. It is on Marianna 2624, which I don’t know if it matters.
Manuange, that’s discouraging on the P de Sep. My tree blossomed but didn’t set fruit this year. I’m hoping next year it will be fruitful. I just don’t want another tree with BK to fight.
Stanley was by far the worst with every single twig infested with Black knot for me. What seems to be happening for me is the Japanese/American hybrids dont ever get it. My Alderman and my Superior have never gotten any Black Knot. There is a Waneta 20 feet away but only two years old that has nothing yet as well. Supposedly Toka is another good one and certainly a good pollinator for the others. My yard is surrounded by wild native plums that sucker everywhere and none of them ever show any knots. They never get fruit though because they get fruit filled with fuzz which I think is Plum Pocket. Ive never seen it on any other plum variety of the 20 or so Ive tried before the Black Knot arrived.
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I believe the native dominant (native to our continent) cultivars tend to be immune or highly resistant. Perhaps it is a disease that is a problem here because of imported plums, instead of the other way around. J’s and E’s just haven’t evolved with BK.