I'm not that familiar with a lot of the insects and diseases that plague gardenias. Mine had mealies/aphids before. But could it be "Powdery Mildew"? Here's a link from Wikipedia with pics, you can see if it looks like what yours has.

Maybe someone else with more knowledge will answer.

Good luck

Here is a link that might be useful: Powdery Mildew

Thanks for the link, but it isn't powdery mildew. I have a couple of pictures that I took, but I can't get them to attach here, otherwise I could show you.

Mudrner, w/o a pic it's hard to tell..I'm guessing either mealy or white scale..mealy is more common with Gardenias, but it could be either insect.
Scale resembles lumps/bumps on a leaf/stem. Some are hard shelled, others soft.
Mealybug reminds me of patches of cotton.
To test for scale..Scrape..scale can be removed using a fingernail. They're semi-round, and detach as one piece.
I use Fish Emulsion to rid scale by spraying entire plant..Mealy's are a pain in the, you know what. I haven't come up with a home-made remedy to rid them.
Ppl on the Hoya forum swear crushed, Scented Geranium leaves keep Mealy away from a plant..
In the meantime, try figuring out which type of pest it is.
If it were my plant, and I suspected Mealy, I'd swipe areas w/a cotton ball or Q-Tip dipped in Rubbing Alcohol..Then, take plant to the sink/shower, add soap, rub into leaves/stems/branches, and hose off..

BTW, do the bugs move around, fly, seem immobile? Toni

Thanks Toni,

I see no movement at all and no sign of flying bugs. I did scrape off one bit and it was hard and flaky. I am beginning to think it is not scale. I have used a magnifying glass to really see it well and it is just white patches, irregular... like dry skin! I'll keep watching it and maybe try the fish emulsion.

Thanks

Can you email me the images?