urgent mildew on maple problem

kr0nic · White Belt Joined: 11 Apr 2008 Posts: 2

Hi everyone, this is my first post.

I have an acer palmatum.

I have re-potted it about 6-7 months ago and i water it whenever the soil is dry (I also water twice with 10 minute intervals); water more in summer than other seasons. It is planted in a generic bonsai soil potting mix.

I am living in Melbourne, Australia.

The problem is:
My maple is a relatively small (20 cm high). During the mid-summer it some of the leaves got infected with "powdery mildew" (100% sure), so i cut off all the infected leaves and burnt them.

Now it's autumn, my tree is having a hard time recovering and the mildew is back! worse than ever. I have recently changed the position of the maple, from a shady wind protected spot, to a spot with higher ventilation.

I am not sure what to do now. Fungicide? Or keep cutting the leaves?

I am very careful to not water the leaves and try to keep the humidity as low as possible to stop the mildew from spreading.

Please, I am in dire need of advice.

imholte

I had a very serious problem with powdery mildew on my african violets. Keeping them in a dry location did not make a difference, they say that airflow helps, but I still had it under the leaves and along the stems which caused problems with new leaf growth and flowering. So I ended up using a garden center spray fungicide that listed effective against powdery mildew.

(Im sure some of our professional gardeners know more, even organic.)

kr0nic · White Belt Joined: 11 Apr 2008 Posts: 2

Hi imholte, thanks for your reply

do you remember the name of the fungicide that you used? I read on this forum about sulphur usage but I'm not too sure..

Was the fungicide you used really effective?

imholte

Yes it was very effective, not sure on what it was called...

Stymie

The fungicide has to be specific for the job. You are doing right by burning the affected leaves, never put them in the compost heap. This link may be helpful:- http://plantclinic.cornell.edu/FactSheets/powdery/powdery.htm

emorrin

I have had powdery mildew problems in the past and a copper based fungicide seems to work rather well. I have used it on a ficus, rose bush, and fukien tea (Carmona microphylla) without any issues. The Carmona microphylla is usually sensitive to most fungicides and insecticides and it didn't lose any leaves. Not sure about the sensitivity of Maple leaves but I wouldn't think it would hurt it, just as long as you don't spray it in direct sun light. It usually takes a few weeks with a once a week application and the powdery mildew is then history.