Jai_Ganesha said:Here is a picture of the foliage rotting. As you can see, it starts out as powdery mildew and then progresses.
Hi Jai,
Well, that is a graphic view of a serious foliage rot problem. However, I did not see anything in that picture that looked like Powdery Mildew to me. This is how Powdery Mildew looked when it started on some of my indoor zinnias.
As soon as I saw those PM spots, I started including Tebuconazole in my plant water and the problem ceased to exist. Powdery Mildew is actually rather easy to control in zinnias, and, ironically, water on your foliage is a good control for it. It is amazing how many garden authorities caution against getting your zinnia foliage wet as a possible cause of Powdery Mildew. That misconception has grown to become an urban myth. Notice that in this article, in the Cultural Practices section, it says that
"In fact, water on plant surfaces for extended periods inhibits germination and kills the spores of most powdery mildew fungi."
http://ipm.ucanr.edu/PMG/PESTN...
Wet foliage is conducive to many zinnia foliage diseases, but Powdery Mildew is not one of them. And I don't recognize Powdery Mildew anywhere in your photo. That black stuff is undoubtedly dead leaf tissue, but the causative agent is a mystery to me. I'm not sure the villain in this is known yet. Do you have a County Agent you can show this problem to?
ZM
