Japanese Maple Distress Call

[pureheart]

Hello Bonsai Friends!

I’m seeking advice on what to do... every single year in autumn I get mildew on this jp maple and every year I stress on how to fix it... now the question is .... should I even bother given that it will lose its leaves? Does this debilitate the tree ? I tried before to spray a solution of water and milk but don’t think it worked... more importantly why do you think i get it every single year???

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[longd_au]

Looks like mildew or a similar fungal infection. Probably from the cooler temp and continuous moisture and less sun.

[Boics]

Air flow and moisture is often the reasons.
I'd be trying to improve air flow and reduce moisture.

Tree looks plenty health - I can't see this being a problem.

[pureheart]

To be honest the tree is almost always in full sun, maybe the airflow is not the best but as many people the tree shares the bench space with other bonsais... I also tried to decrease the amount of water I’m watering with and clearly no water on leaves... I’m not really sure what else to try unless I have to change entirely position for the tree ...


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[TimS]

I always get powdery mildew on my Japanese Maples at this time of year like clockwork.

I haven't found a real solution yet to give you, I've done the increase airflow/ reduce watering/ minimise water on leaves to some small success.

I have tried chemically spraying it with varying results, but the best i can offer is what has worked in some limited way for me and that is: On a healthy tree ONLY, full defoliation of the entire tree, spray the entire tree well to get as much of the spores that may be on the buds, move to a protected position until the new leaves have hardened off and back off the watering as well.

Often mine get it so close to autumn leaf drop that i don't bother defoliating and trying to get the flush, i just move the affected tree(s) away from unaffected trees and spray the affected tree. This at least stops or slows the spread of the spores to other trees, but still i don't get the full autumn show. In winter i do a preventative spray to try to kill any dormant spores sitting on buds that will transferred to the new leaves in spring too.

As i say i still get powdery mildew so it's not going to be a cure all for your powdery mildew issues.

[pureheart]

I always get powdery mildew on my Japanese Maples at this time of year like clockwork.

I haven't found a real solution yet to give you, I've done the increase airflow/ reduce watering/ minimise water on leaves to some small success.

I have tried chemically spraying it with varying results, but the best i can offer is what has worked in some limited way for me and that is: On a healthy tree ONLY, full defoliation of the entire tree, spray the entire tree well to get as much of the spores that may be on the buds, move to a protected position until the new leaves have hardened off and back off the watering as well.

Often mine get it so close to autumn leaf drop that i don't bother defoliating and trying to get the flush, i just move the affected tree(s) away from unaffected trees and spray the affected tree. This at least stops or slows the spread of the spores to other trees, but still i don't get the full autumn show. In winter i do a preventative spray to try to kill any dormant spores sitting on buds that will transferred to the new leaves in spring too.

As i say i still get powdery mildew so it's not going to be a cure all for your powdery mildew issues.

Thanks Tim! It sounds like I’m doing all the right things then! Do you get it on all your maples or just some? What do you spray the tree with and does it work?


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[MJL]

Howdy Pureheart. My Japanese maple forests are prone to powdery mildew too. I don’t worry too much - upon first sight, I usually spray on a course of Nature Soap (or sometimes Pest Oil) - right from when I first see it and that usually controls things; it at least seems to stop the spread. When I say ‘a course’ - every week or so for 4-6 weeks.

The mildew was worse when the maples were situated with other trees and less airflow.

Now the forest sits by itself, morning sun and reasonable airflow (for a courtyard) - that said, I water the whole banana. Everything - leaves and all - which means it’s a pretty moist environment - so I’m never surprised when the mildew pops up. Here a couple of photos this morning show first and a few crud leaves in the mix.

I’ll live with that. I won’t defoliate now as the trees will shed its own leaves soon enough.

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It’s also worth noting that I reckon it’s been a weird season for Japanese maples here in south east Melbourne. My and my Neighbour’s garden maple trees have generally struggled and indeed, thrown long, straggling flushes of new growth (with big leaves?) at strange times over summer. Who knows - it’ll be something to do with irregular heat and water.

Don’t stress too much Pureheart. You’ll get on top of that mildew in due course.


Bonsai teaches me patience.
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[tgward]

there was a time in the vineyard here in the Riverland when overhead watering was seen as beneficial in washing the spores from the leaves-----and less chemical needed -possible prevention by more direct jetting of the leaves in an open airy situation?

[pureheart]

there was a time in the vineyard here in the Riverland when overhead watering was seen as beneficial in washing the spores from the leaves-----and less chemical needed -possible prevention by more direct jetting of the leaves in an open airy situation?

I thought that watering the leaves would create a more humid environment and therefore facilitate the mildew...?

[KIRKY]

A couple of things I have found with powdery mildew. In winter when the trees are bare spray with sulphate I spray the same stuff I use on my bare roses including spraying the top of the soil. By doing this I find there will be no powdery mildew the following year. Also for airflow during the growing season thin out the larger leaves 50% roughly this will help.
Cheers
Kirky

[pureheart]

A couple of things I have found with powdery mildew. In winter when the trees are bare spray with sulphate I spray the same stuff I use on my bare roses including spraying the top of the soil. By doing this I find there will be no powdery mildew the following year. Also for airflow during the growing season thin out the larger leaves 50% roughly this will help.
Cheers
Kirky

Thanks Kirky, are you saying to cut in half the big leaves or to remove overall the big leaves by 50%?