My purple cone flowers are starting to bloom. I have seen some white powder on this plant stem

[midnight]

and was wondering what this is. I wiped it off, but if any one with purple cone flowers knows what this is… Please post. Thanks.

[The Velveteen Ocelot]

1. Probably powdery mildew.

It's unsightly but it won't kill the plant. It's most likely to turn up when it's hot and damp and the plants are close together. https://en.wikipedia.org/wiki/Powdery_mildew

[midnight]

3. Really happy to read that it won't kill these flowers. It is hot and plants are close together. I

was going to work on moving plants further apart…

[alfie]

2. I have a lot of purple cone flowers...

but haven't noticed any white powder. I will go out in a bit when it cools down some outside and see if there is any. I have heard of powdery mildew on leaves of different plants, but not the stems.

[midnight]

4. I think mine are too close together...

[glinda]

5. Yes. After they dry, thin them. With powdery mildew on some of my past

plants, I have seen some of them "disfigure" and become disease prone. Best to thin.

[midnight]

6. Yes… I was thinking of digging some up and transplanting… I just love them so much…..

[arachadillo]

7. Cone flowers

I agree with the thinning, sometimes high density flower patches promote powdery mildew just because all the parts of the plants are not getting sufficient sunlight.

Over watering the plants also sometimes causes the problem as well as having weeds or other plant stuff near the garden.

Finally, if the problem is way to big to deal with and the garden patch growing the flowers is important for any reason, including aesthetics, there are a handful of organic fungicides that can be used for prevention. As long as the fungicide is for any daisy or more generally any garden perennial, it should work good.
http://greennature.com/article267.html