Powdery mildew - should it stay or should it go?

Hello everybody! First post for me here.

I noticed on my red maple signs of powdery mildew. I was about to treat it but I read somewhere that if Autumn is close (here in UK it's already pretty cold), treatment could be avoided.

I would still intervene to avoid contamination to braches too and I was wondering if baking soda+mild soap+water (+olive oil?) or other "home made" potion may suffice.

Thanks in advance for your help.

Maples are prone to mildew, and they struggle to recover.

At this time of the year the tree starts the dormancy cycle. The leaves will go brown as the tree removes the sap from the upper section and flows it down into the roots for storage over winter.

Thus you will want to leave any healthy leaves - as many as possible.

But remove and throw out any dead or badly infected leaves and cut off and discard any infected branches. When you cut off an infected branch leave a good margin, so cut a bit deeper into the healthy side.

Treat the tree with a fungicide.

Then keep it somewhere semi-shady and airy - fungus likes shade and still air.

Fingers crossed.

Dear Brendan,

Thank you very much for your help and advice: much appreciated and very clear.

Would you suggest a "home made" solution or a specific fungicide (I read about Bayer fungus fighter plus but I'm not sure).

Thanks again,

Y.

Buy a good quality fungicide that is recommended for this type of fungus. You will need to re-treat the tree in the spring anyway, plus it is handy to have some if you keep bonsai.

I generally have a good fungicide, and a systemic pest killer on hand.

Thank you for this. All clear: in my case I think there is an issue with ventilation (I'll try to find an alternative location).

Kind regards,

Y.

You could also thin out the dense areas by cutting off half of some (individual) leaves, increase the air circulation.

And do not water the foliage. Clean your tools after work so you don't spread the fungus.

Thank you Augustine for the advice: appreciated!

I finally moved the tree to a less protected position; now it's just a question of convincing the Wife to buy a nice bonsai display table!

The Maple seems to respond well to the treatment: I used Bayer fungus fighter plus. I originally intended to use a home made solution, but I eventually saw that the RHS (Royal Horticultural Society) was quoting this product among remedies agains mildew.

Kind regards,

Y.

Yamato wrote:Hello everybody! First post for me here.

I noticed on my red maple signs of powdery mildew. I was about to treat it but I read somewhere that if Autumn is close (here in UK it's already pretty cold), treatment could be avoided.

I would still intervene to avoid contamination to braches too and I was wondering if baking soda+mild soap+water (+olive oil?) or other "home made" potion may suffice.

Thanks in advance for your help.

I realize this post is several months old already. But I thought I would chime in.

The home remedy spray should work to reduce the visible symptoms of powdery mildew or downy mildew. Unfortunately it only kills off the external portions of the fungi as it emerges from the leaves to produce spores. The home remedy will not kill the fungus living inside the leaf. You will have to treat weekly or more often to prevent the fungus from producing spores. This home remedy is safe and non-toxic, it is used on food plants that whether the fungus is present inside is not an issue, it keeps appearances acceptable and allows the plant to be harvested. I've seen marijuana growers use this type of home remedy to keep the plants from deteriorating to the point of not being harvestable. Short term. The cycle for marijuana is only 16 weeks from cutting to harvest. You would then thoroughly clean the grow area, and start with a fresh batch of cuttings from stock plants that have not been infected with mildew.

We need our maples to survive more than a few weeks to harvest. We would like years. You need to use a systemic fungicide. Every state and country has their own regulations as to what is allowed. So my recommendations may or may not be available in your area. Mancozeb and Daconil are two trade name fungicides that work. there are many more that work. Hit your local supplier, and read the labels, READ LABELS BEFORE YOU BUY. If the label does not list mildews, then it will not work against mildews. The label should also list plants the fungicide is safe to use on, or list plants it should not be used on. READ.

Different formulations of the same chemical may or may not be effective because of the way the chemical is delivered, so read the labels. I would check the labels of your locally available Mancozeb and Daconil first. These are both less expensive and more widely available. But they are not available everywhere. Local regulations vary.

I usually have very few issues of fungal diseases on my maples.

One of the best preventive treatments is Bordeaux mix (copper sulfate) just after leaf fall and before budbreak.

This is one of the best, and much less harmful for the environment than other "chemicals" that I only use when things get out of hand, which is very rare : for most healthy trees, this is sufficient, although some cultivars ('Taylor' seems to be one of the worst), whatever, they're very difficult to keep.

But for the plain species, and most cultivars, Bordeaux mix is the most efficient.

I thought I would like to show some photos of my juniper which is presenting some kind of whitish "dust" on foliage at the tips of two branches.
If I rub the scales with my fingers the dust is easily wiped away.
It's like a light which substance has fallen on the foliage...
The same happened in the past, almost two months ago on those two branches and I have cleaned the "dust" from the foliage, but now here it is again...





I know photos are not clear and difficult for you to conceive what it is.... but any thoughts are appreciated.

Leo Schordje wrote:

Yamato wrote:Hello everybody! First post for me here.

I noticed on my red maple signs of powdery mildew. I was about to treat it but I read somewhere that if Autumn is close (here in UK it's already pretty cold), treatment could be avoided.

I would still intervene to avoid contamination to braches too and I was wondering if baking soda+mild soap+water (+olive oil?) or other "home made" potion may suffice.

Thanks in advance for your help.

I realize this post is several months old already. But I thought I would chime in.

The home remedy spray should work to reduce the visible symptoms of powdery mildew or downy mildew. Unfortunately it only kills off the external portions of the fungi as it emerges from the leaves to produce spores. The home remedy will not kill the fungus living inside the leaf. You will have to treat weekly or more often to prevent the fungus from producing spores. This home remedy is safe and non-toxic, it is used on food plants that whether the fungus is present inside is not an issue, it keeps appearances acceptable and allows the plant to be harvested. I've seen marijuana growers use this type of home remedy to keep the plants from deteriorating to the point of not being harvestable. Short term. The cycle for marijuana is only 16 weeks from cutting to harvest. You would then thoroughly clean the grow area, and start with a fresh batch of cuttings from stock plants that have not been infected with mildew.

We need our maples to survive more than a few weeks to harvest. We would like years. You need to use a systemic fungicide. Every state and country has their own regulations as to what is allowed. So my recommendations may or may not be available in your area. Mancozeb and Daconil are two trade name fungicides that work. there are many more that work. Hit your local supplier, and read the labels, READ LABELS BEFORE YOU BUY. If the label does not list mildews, then it will not work against mildews. The label should also list plants the fungicide is safe to use on, or list plants it should not be used on. READ.

Different formulations of the same chemical may or may not be effective because of the way the chemical is delivered, so read the labels. I would check the labels of your locally available Mancozeb and Daconil first. These are both less expensive and more widely available. But they are not available everywhere. Local regulations vary.  

Thank you for this! I will check it out.

Kind regards,

Y.

AlainK wrote:I usually have very few issues of fungal diseases on my maples.

One of the best preventive treatments is Bordeaux mix (copper sulfate) just after leaf fall and before budbreak.

This is one of the best, and much less harmful for the environment than other "chemicals" that I only use when things get out of hand, which is very rare : for most healthy trees, this is sufficient, although some cultivars ('Taylor' seems to be one of the worst), whatever, they're very difficult to keep.

But for the plain species, and most cultivars, Bordeaux mix is the most efficient.

Thank you! This is treatment I will definitely try (hopefully the new position for my maple should help... finger crossed!).

Kind regards,

Y.

I've used them all, but to no avail. Too wet, too still, too dark, too long. It gets deep into the wood and I end up burning them. Got a 300 year Ohi'a on the block.