Phlox paniculata

diseases that this perennial is subject to and how to treat them. Powdery Mildew? and wilting of leaves?

The best way to prevent powdery mildew is to buy cultivars that are resistant to it. If you have susceptible cultivars they're probably going to wind up with it at some point no matter what you do. 'David' is one cultivar I know of that's supposed to be resistant, but there are others too. Or are you talking about a plant you already have and it has those symptoms? I know some people spray milk on the leaves to help with the powdery mildew, but fungicides might work too, check the label for one that lists powdery mildew. Wilting leaves would more likely be a symptom of a watering issue and won't be helped by milk or fungicide sprayed on the leaves (most likely too much water rather than too little if the plant also has mildew)

If the mildew or other fungus is thick enough, it can also cause wilting of the foliage as it can be suffocating it.

Here is a formula for treating Powdery Mildew which will actually make it vanish when you spray it on. I use it on P. paniculata and roses and it works great.

For ONE gallon of spray, mix the following into one cup of water: Add ingredients in this order:

1 1/2 tbs. baking soda
1 tbs. canola oil
1 tbs. insecticidal soap
Then add 1 tbs. white vinegar. ( Do this LAST...or it will foam all over the place.)

Stir together and then add enough water to make one gallon of spray.
Apply with tank sprayer on days when temps. are lower than 85*
Thoroughly soak the foliage and let dry.


There are different variations of this concoction, but I've had excellent results with this one. The baking soda sucks the moisture out of the fungus and kills it.


This message was edited Aug 12, 2008 9:41 PM

Thank you so much for the information on my Phlox disease issues. I will try it right away and let you know how it went.

Does it have to be canola oil?

To be honest with you, I don't know. I've only used canola oil....AND, I don't even know what the difference is between canola oil and regular vegetable oil, since I don't cook. Someone gave me a huge container of canola oil and I still have most of it left.

I guess you could mix a batch with regular vegetable oil and see if it works, but test it on a small not-so desirable plant maybe ?

The oil is only in the formula to act as a surfactant...to make the spray adhere to the foliage...which is temporary at best since the insecticidal soap will counteract the oil so you don't have a greasy look leftover.

But all my plants are desirable...lol