Black Knot in Burbank Plum?

11 years ago

I planted this potted Burbank Plum from a nursery end of season sale last fall (not the best choice i know) It seems to be doing ok, but is growing fairly slow, about 8" of growth at each tip this year, in comparision to a Shiro planted at the same time which put on about 15" of growth this year. They are in the same approximate locations. Considering the very mild winter here last year (-20C max for a very brief spell), i dont think it suffered winter damage. My concern is a black spungy growth? located at the graft union i found today. It dosn't really look like the pictures of black knot i found on the internet. Am I paranoid, or if it is black knot, what can i do about it at that location? My understanding was that Burbank was fairly resistant to black knot.

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Comments (9)

alan haigh
11 years ago
It is black knot, but don't be paranoid, there's no plot against you, and as long as you cut out galls as soon as they are visible you'll hopefully have no great difficulty keeping it under control. Cut to healthy wood (look for stain running up and down from the wound).

Open pruned trees with good eastern sun often are less susceptible.
tbuch
Original Author
11 years ago
Thank you Harvestman, this tree will get excellent eastern sun and I'll train it to an open centre. I'll try shaving it off tomorrow.

Thanks for the advice and reassurance.
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Bradybb WA-Zone8
11 years ago
I see that on your tree tbuch and it makes me wonder if it's on this 4-way Plum and Apricot.It isn't really black and is kind of dry and crumbly.It's right at the grafts. Brady

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theaceofspades
11 years ago
I agree with harvestman, I'll add I have never seen black knot start at the base of a tree before. Is that forest mulch you are using. Wild Cherry is the vector for black knot in my orchard.
alan haigh
11 years ago
I've never considered mulch as a potential source of BK innoculum but now that you've mentioned it, Ace, fresh chips with native cherry in the mix could be just that.

Brady, that does look like black knot, and it is very serious. It looks like the infection came from the nursery.

If the black knot girdles the grafts in a complete circle they are toast.
tbuch
Original Author
11 years ago
The mulch i used was store bought cedar mulch. i'm not awear of any wild cherries in my immediate area, but there is some bush pretty close. in my veg garden pathways (about 60' away) i did lay down some wood chips that i salvaged from roadside maintenatce work, it could verywell have contained wild cherry in it. Planning to trim that black knot away today.
Good luck Brady with your plum/apricot
On another note, we recieved our first fall frost this morning.
alan haigh
11 years ago
If you see black knot galls on nearby bushes I would be concerned but otherwise not. I don't worry about healthy cherries infecting plums but sometimes the galls are up so high they are hard to see on the trees.
Bradybb WA-Zone8
11 years ago
Thanks harvestman.Your insights are very much appreciated on this forum and elsewhere I'm sure.
I did a little reading about Blackknot and one source said to wait until Winter to deal with it.That way the spores will be dormant.It also mentioned to spray with some fungicides,one being Chlorothalonil,which I have in the form of Bonide's Fung-onil.Does the Winter work sound realistic or is more immediate attention necessary? Thanks,Brady
alan haigh
11 years ago
Chlorothalonil is the one always most highly rated- most fungicides don't work at all, but even CTL doesn't seem to help much and isn't supposed to. I actually spray the cuts with it when I remove the galls.

If I wait until trees are dormant the disease gets away from me in highly infected orchards, but probably no harm in waiting at this point of the season.

I will assume the best strategy is to remove the spore producing galls from the orchard as soon as possible until I see some actual research telling me otherwise. Why would you wait when galls are spreading innocculum to other trees? It's not like cutting them will increase the spread- it should decrease it. Also, during the growing season the galls also grow, sometimes girdling entire branches.