Is this powdery mildew on my maple during air layer

[ianmcglocklin]

Hello everyone! And happy Father's Day to whoever it applies to. So I started two air layers on this nursery bought green Japanese maple a week and a half ago, and noticed this white powder/residue on some of the leaves. At first I thought maybe the wind caused some rooting hormone to get on the leaves but now I believe it may be mildew, and has appeared on red maple next to it. The affected leaves are above my air layer locations and I'm wondering if it is what I believe it to be, and if so should I remove the affected leaves as I've read to not remove foilage during air layering.

 

[crab apple]

The pics don't really show much but your describing mealy bugs. Mess with them up close and see if anything moves.

 

[ianmcglocklin]

Here's a close up. When I rub my finger across the leaves it wipes off on my finger, so I figured mildew, but upon inspecting on opposite side it's not quite as spread out and equal. Mess with the white to see if anything moves?

 

[ianmcglocklin]

I don't see anything that resembles the white bugs I see on Google photos on my plant, but it is definitely spreading, And holes appearing on leaves

 

[crab apple]

The mealy bugs on my trees are more on the stem or under the leaves. If you mess with them you can see them moving or in some cases fly off.

 

[MrBonsai19]

Yes it does look like Powdery Mildew to me. I have some show up recently on my JMs and I am also in the Bay Area. I think the morning fog makes it a particular challenge for us as there is going to be cold shady and wet conditions most mornings around here. I believe it is something that has to be cut off and I wouldn't worry too much about your air layers being affected. There is still a ton of time left in the season for the layers to develop and ultimately if your roots haven't progressed enough to separate this Fall you have the option to wait until next year. The layer will continue to progress even if not separated so it's not completely lost time.

As for the mildew if you are seeing issues with it, the best step is to remove what is affected and then start spraying monthly. I use Phyton 27 monthly on the maples for this. But there are milder products out there like Bayer 3-in-1 that can work. Spraying prevents spread but I dont think it will save the affected leaves they have to be removed. If you dont remove them it will spread for sure and risk even more leaves becoming damaged and unable to photosynthesize for your air layer.

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[ianmcglocklin]

Thank you! It first showed up on that tree a day or so after I started the air layer, I also turned the plant a bit that day so all long new shoots are pressed up against the side of my house going vertical so that the layer was easy to inspect visually, which I'm sure decreased the free air flow for the plant and the air layer being wet increased moisture so it makes sense that PM is what I'm seeing. I was hesitant to remove the first handful of branches I noticed with it because it was above my air layer and I've read it's not recommended to prune or reduce foilage during air layer, however there is so much foilage on each section above the layers that I guess it really shouldn't reduce photosynthesis back to layers. This is one of my first air layering attempt in years, I tried a few times at the beginning of my bonsai journey but back then I was so overeager to attempt all sorts of techniques I really had no idea clue the why or the how for what I was trying, this time I am optimistic and much more confident for the chances of success.
So I will cut off all the shoots and leaves that have signs of the mildew and keep a close eye on them. Ive read people mentioning hydrogen peroxide spray for mildew also, if python works for you for the same issue on JMs in the same area I live I will try it as well! Thank you for your input and advice.

 

[ianmcglocklin]

What part of the Bay Area do you live? And do you attend any clubs or classes around here? I've been wanting for years to attend the lake Merritt classes but haven't, and also as I have recently got back into the hobby and trying to learn as much as possible I saw that Boon is out of Sacramento and does classes!

 

[MrBonsai19]

the preventive sprays have worked very well for me on everything except this one seigen. It is I think more prone to powdery mildew than the average maple.




For what its worth I am still proactively removing all the shoots that show symptoms including the one in the picture above, and coincidentally I am also in the process of air layering this tree.

Your layers look good to me, although I would take the additional step of wrapping them in aluminum foil because roots do grow better in the dark . especially in the bay area we don't have to worry much about temperatures getting above 100F when the foil could overheat your layer.

 

[ianmcglocklin]

I live in the East Bay, and during the summer it often times does get above 100 degrees here but hasn't been yet this summer, I've heard of people putting aluminum foil around plastic, your saying that it would overheat it though right? If it gets over 100?

 

[MrBonsai19]

Um well that comment about overheating was very theoretical. I have read about it being an issue for layers in very hot areas like Dallas and Arizona. The foil works both ways in terms of insulating the layer from heat while temperatures are rising. But if temps are hot enough to get the layer to a very high temp over a prolonged period, then the foil does the opposite and insulates the heat from dissipating. Either way it's not something I've practically worried about in the Bay Area I wrap all my air layers ** in aluminum foil. I don't have much practical experience with what those thresholds are where the foil would start to cause an issue.