Hello! Could anyone give me advice on this bark situation? Mainly I am curious if it is disease of some kind or more of a physical damage (sunscald, etc.) -JM Osakazuki -Has been in ground for two years now, is throwing out splendid growth in all directions, and both above and below this discolored spot on the trunk (despite Minneapolis 4B/5A climate).
Hello it looks like Pseudomonas to me..I’ve had this on several trees and I believe it will end up being terminal to whatever’s up stream of it (because it is so advanced) I caught it early on a JM where it covered 30% of the circumference, I cut it away using a razor blade (following good advice from @alank and @emery) and it appears to have worked but yours looks more advanced. I can’t tell from the photo whether the affected area is the main leader from the graft, or a branch..if the latter I’d cut it off several inches below. There appears to be discolouration to the bark above the affected area, this can be a precursor to the branch dying. You could also apply Bordeaux mix and see if it helps. Sorry my synopsis is a bit bleak
Even if bleak I really do appreciate the information. Can I apply a Bordeaux mixture now or does the tree have to be dormant?
Is it the leader from the graft? How far round the circumference does the disease go round? Whats below the diseased section? Enough to cut it off 3 inches below with some branches/buds below? If so I’d cut it off. Bordeaux anytime
Pseudomonas is usually an issue in late winter or early spring but obviously not limited to that period. It could be pseudomonas bacteria, or another similar bacteria, but could equally be sunburn or some such. Bordeaux mixture will not do any harm to the maple so there is no risk in using. Some pictures of the whole tree and info as to sun exposure of the affected area, info and pictures of any dieback above the discoloured area, etc. would help to increase the accuracy of any advice....
I agree with @maf , there's no reason not to treat with Bordeaux mix, while you still see spots of black especially. But to my eye this looks mostly cured. I suspect either good cambium or completed compartmentalization under the scaly area, because it looks stable. Usually active infections will show black at the edges, attacking smooth, clean bark. Every once in a while I get a graft where the understock has this kind of damage. I have one now. The top and root both look normal after a year, so I think it's likely that mine will be OK.
Thank you for the replies, all of you! Here is a photo of the full tree, with the area in question visible. Overall, it looks very healthy to me, which is why I didn’t think to inspect. The leaves show a little bit of spottiness, but I’m not surprised as it has been an extremely rainy summer in the Midwest and our drainage is fine but not outstanding.
Oh, and @maf asked about sun exposure. It faces east. Gets pretty much full sun in the morning and is shaded by afternoon. No dieback above the area, as the photo shows.
The maple does look pretty healthy. I feel the best way forward is just to monitor the discoloured area and optionally apply a copper compound. If it takes a turn for the worse then by all means get out the pruning tools, but for now just wait and see.
