Powdery Mildew on Rosemary

My rosemary has powdery mildew.
This seems bad, but it has had powdery mildew for about 6 months. Because the powdery mildew didn't do anything but make the leaves look mouldy, I have left it alone. Had the leaves started dying, I would have tried to solve the problem immediately.
Anyway, I looked up the words "powdery mildew rosemary" at ask.com, a search engine. The search engine led me to a page which suggested several remedies including 5 mL baking soda to 1 l of water, drench the leaves every three days until the problem clears up; and the use of sulphur.
I will try the cheap soda trick first. If nothing happens in a month then I will start to dust the plant with powdered garden sulphur.

Appendix: Feb 13/07
When I applied the mixture of soda and water to the two infected rosemary plants, most of the infected needle tissue blackend immediately. This resulted in the death of one of the plants, as it was very infected. On the other plant, the needles were only partially coated with the powdery fungus. Hence only half the needle died. It is important to note that not all the needles which were infected died, but about half of them. On the plant that died, all of the surviving needles were old needles which were likely to be shed this year. So the surviving seems in fair health. There is one loonie sized spot of powdery mildew which has persisted about 6 applications with the original mixture of soda and water.