Question
Okay, I'll try to explain this as clearly as I can, but I'm not an expert, and I don't know the name of the plant. :-)

I am living in Israel and maintaining a garden planted be somebody else. One of the shrubs (hardy bush with shiny hard leaves) has developed a problem which I thought was mold. Its a white powder which brushes off easily. Is this a problem?

We had a gardener come and look at it, and he didn't seem to be concerned. He thought it might just be something the plant produced itself, out of stress. He had a name for it, but it was in Hebrew- and my language skills don't extend to gardening terms yet!

I know this may be difficult for you because its out of  your zone, but I thought I'd give it a shot.

If you need more description of the plant, I could probably do that. As  to zone? Ummm- arid/semi-tropical. We are right on the line between the two I think.

Answer
Powdery Mildew?

Depending on the plant, it could be a problem, or not.

Any time you cover leaves with anything, you keep them from working effectively.  Mildew stops a lot of Photosynthsis. Now you have a stressed plant, weakened, with less energy, due to lack of sufficient light.

What's more, Mildew once there is hard to remove.  What you want is to keep it from spreading more than it already has.

Got Milk?

Spraying leaves with MILK sometimes helps, depending on the KIND of Powdery Mildew you are battling.  Not all unfortunately, and not that effectively, either.  But it's worth a try, and easy to obtain.  Put some in a spray bottle and shoot, saturating leaves above and below.  It will alter the pH of the leaves, among other things, and hopefully get the Mildew somewhat under control while you figure out Plan B.

Take a look at the leaf on this web page. Look anything like yours?

www.greencure.net/what_is_greencure.asp

Many people spray affected plants with Baking Soda -- Sodium BiCarbonate.  But tests using Potassium Bicarbonate have been far more promising.  If you can get your hands on any of this stuff, you will be doing the owner of this plant a big service.  It's rarely done, and yet it's quite state of the art.  Not to mention nontoxic.  And generic.

Have you got access to it?

Any thoughts?