Any horticulturalists in the house?

[PeterB]

What is this stuff on my strawberry geranium, and how do I get rid of it?:

http://imgur.com/a/QS4Nw

[freeradical]

Powdery mildew?

[OWC Jamie]

yeah that looks like powdery mildew. You can hit it with a fungicide.
Milk diluted to 10% with water is supposed to help and sprayed on it every couple of days is supposed to help.
It commonly plagues zucchini leaves but I've never seen the milk spray work.

Dampness, especially overnight in cooler temps is an environment it thrives on.

[neophyte]

We use Safer brand fungicide for this. It's safe for organic gardening, relatively environmentally friendly.

[Lizabeth]

Do you have a non-bigbox local nursery you can visit with a leaf? It does look like powdery mildew

http://www.wikihow.com/Get-Rid-of-Powder...-on-Plants