Zinnias seem to me to be more susceptible to powdery mildew than any other plant I grow and the method I use to control that is to spray either a mixture of 1 teaspoon baking soda mixed in 1 quart of water, or a 50/50 mixture of fat free milk and water, every 5 to 7 days as needed if the plants are infected or every 7 to 10 days if no PM is seen but the weather conditions indicate it could be.
I think that leaf spotting will go away with the PM.

I'm curious as to what kind of zinnias you're growing. Some are much, much more susceptible to typical diseases than others. On the other hand, there are others that seem darned near invincible! One of the best methods of preventing disease occurrence is to select those resistant varieties in the future.

Corn meal has been proved to be a very good weapon in our battle against certain fungal disorders. Incorporate it into the soil when planting your zinnia (or before sowing). You can also soak it in warm water to make a corn meal 'tea' to be used as a spray. Corn meal is not effective against powdery mildew, to my knowledge, but the assortment of diseases that fall under the term: 'black spot'.

If you haven't tried the "Profusion" series of zinnia yet, you should treat yourself next season. I've never seen fungal diseases of any kind over the several years I've grown these plants. They bloom early and continue on and on until frost. "Magellan" zinnias have been PM free for me but developed black spot the first year. I've used corn meal ever since with success.

I'm sure that there are other resistant hybrids and cultivars...hopefully folks will suggest their favorites.

I will second the Profusion series, only zinnia I have ever grown that didn't get PM. I will have to look into Magellan.

In my own experience once the PM sets in, it doesn't go away, but your mileage may vary.

Anyone have a picture of what Zinnia PM and/or leaf spot look like? I have zinnias that have leaves that turn brown/gray as if they're dry or something but it looks like PM might be the culprit.

Zach w

Sounds like it's a good time to try Serenade and see if it works.

What is PM?

Albert....PM means powdery mildew if the discussion is pertaining to that particular disease. Make sense?

I raise the Oklahoma zinnias and they resist mildew usually until late in the season. They bloom profusely. They are not giants nor midgets...very nice.