Hi all The very cold snap has ended (for the time being!), and I went out to check my trees. To my despair, I've found many trees with some dark spots on the branches that weren't there a few weeks ago. Are these something to worry about? Did they just appear because of the frost? Has some disease started? Shall I cut all the affected branches? Thanks for your help Here are a few photos showing what has appeared on several trees (i've circled in red the new spots)
Hi Chris, IMO your maples are suffering from Pseudomonas syringae. This can be treated with a fungacide, preferably copper based. A root drench and a canopy spray over the next couple of months should stop the spread. ( Once every two weeks). Unfortunately these fungus attacks do happen in prolonged wet or frost periods. So due to this weather the UK has been experiencing, this is my thoughts on what your photos are showing. Some branches might need pruning out in late February, but I would hold off any sugery ATM. Give the fungacide a chance to work.
Hi Chris, Well, ugh. Were these trees well and truly dormant -- that is, had the sap completely descended -- before the big freeze? We have problems here, with some maples, where the bark is splitting because it was still carrying a lot of sap, which then froze. IMHO the black spots are where some bacterial infection has entered into micro-fissures in the bark. The black is dead, but that doesn't mean the entire branch will die. In pics like #3, where it is more gray, the infection may be dying naturally, leaving a spot of frost damage that will heal without issue. Others look a little more dire. I would treat with copper and keep under observation. Hopefully the copper will stop it in its tracks so no major cutting will be required.
Derek responded just before I did... the only difference we have is the copper root drench. I don't recommend this, as I think it can disrupt the mycorrhizal balance in the roots. I don't know that the tree would pick up a lot of free copper anyway, but it would be interesting to see if any studies have been done on the subject.
I do agree E, but as Chris has his in pots IMO I think it's worth the risk. And you can re add mycorrhizal for acidic plants later. I would never suggest a copper root drench into the garden soil as this can be detrimental.
Hi again Chris, just an after thought are these photos of Sango kaku and Bi hoo ? If so, then these two and especially Bi hoo are very susceptible to Pseudomonas syringae and quite severe die back. I have found Bi hoo to be very difficult to keep alive, if you have purchased a bad one. ( Often mass produced specimens for garden centres). I saw many of these for sale today at my local garden centre and all were suffering very severe die back problems. People were still buying them, as the bark was looking bright red and yellows in the Winter sunshine.
Thanks Derek and Emery for your information! That's what I feared it would be. :-( Getting some already. and that's not even really winter yet. For the copper solution, since I don't have hydrated lime, would a mix of 100g of copper sulphate and 10L of water be ok, maybe not this volume, but in terms of ratio. (isn't the ratio 10:10:100 for Bordeaux mix?). That would like a BM but without the lime. Emery, I think these were dormant (or at least, they lost all their leaves in mid-November I beliebe). Derek, yes, the most affect ones were the Bihoos and the Sango Kakus.. I think I saw a Beni Maiko was some spots. I'll check more tomorrow and spray them since it it's quite mild temperatures
I agree with the other comments, looks bacterial and most likely Pseudomonas. As also noted the coral bark types are more susceptible for whatever reason (possibly thinner bark). The final outcome might depend on the weather going forward. Pseudomonas syringae is an ice nucleating bacteria. It is also widely present in the environment, and is present in rain, snow and hail so re-infection after any treatment is a given. Usually the presence of both the bacteria and several degrees below freezing temperatures are necessary for aggressive damage such as you have seen, so if the weather stays relatively mild the prognosis will likely be better. From Ice-nucleating properties: The other thing to be aware of is that the black areas are possible infection sites for other opportunistic pathogens, so keep an eye on this also. I have never personally used copper (or other fungicides) on my maples but can see that it may be helpful to give the branches a spray in this situation. I don't think the type of copper solution would make much difference as long as the concentration was appropriate. Would definitely advise against the root drench though.
Copper sulphate with water to spray is fine Chris. The coral bark maples do suffer more than others, so hopefully your others will be fine. But it won't hurt to spray them if you see a slightest mark that appears to be Pseudomonas.
Thanks so much for your advice! It looks like I'am hitting all the diseases maples can have (verticilum on a tree at the back of the garden (not good!), powdery mildew, and another one with undetermined leaving leaves with brown patches). For the copper solution, I guess that without the lime, it won't stay as long on the branches :-( I normally quite regularly (every few weeks) spray some of the trees with a diluted solution of hydrogen peroxyde. Can the copper solution be used alternatively with the hydrogen peroxyde one (like 1 week one, 1 week the other), or it's not necessary since the copper solution should do the same (and more wrt. bacteria)?
I am in danger of getting off topic here but I do not see the point of spraying hydrogen peroxide regularly on trees. I understand how it is safe in the sense that it degrades to water and oxygen and does not leave toxic residue behind, and sure, it will kill some harmful pathogens but it will also kill beneficial microorganisms just as easily, thus setting up a boom and bust cycle in the microbiome. The complex relationships within the microbiome are still not fully understood, but it is clear that a healthy and balanced system takes some time to establish and forcing a hard reset every few weeks is not in the best interest of the system or the hosts (your maples). It may be that some of the most beneficial microorganisms are among the slowest to recruit and may never become properly established in such a system. Edit: Apologies if this seems like a rant but I am against all spraying (even something as innocuous as hydrogen peroxide) unless there is a specific need.
When making Bordeaux mix the lime acts as paste keeping it in place on the branches. Bit to spray with the lime is very difficult, hence just use the copper in this case.
I agree with @maf posting on this and only to spray if needed. So just use the copper on the affected maples. Hydrogen peroxide is useful for washing the roots if they have some root root. I have carried this out when lifting, and finding a problem whilst root pruning, so it does have some advantages, but not as a regular spraying etc etc.
I'll chime in too, haha. I don't find this off-topic, seeing as how we're talking about how best to care for the trees. I agree, the effects of spraying regularly with hydrogen peroxide range from "none" to "harmful". Think about the very best JM producers, like Vandermaat (and by extension Pat at Hippopottering), in the Netherlands, Choteau in Belgium, etc. These and many others spray regularly with EM (Effective Micro-organisms), which are now widely accepted to dominate "bad" bacteria (like pseudomonas). But at concentrations high enough to do anything, the hydrogen peroxide will kill the good with the bad bacteria, leaving an open field for the ice nucleating varieties in winter. I can see how "spot spraying" HP might be effective prior to beginning a copper regime. BTW, the copper sticks pretty well even without the lime; as Derek said the lime fixes it so that it doesn't wash off in the rain. I have used HP in low solution to water into pots that have had root rot, though not in years, tbh. My theory was that it would bring oxygen into compacted, water-logged soil. Now I'd be much more likely to simply repot a maple in that situation.
