My phlox and dogwood had powdery mildew at some point. It's important to remove all infected leaves and then to apply fungicide on the rest of the plant.

My approach is organic, home-made, and this is what worked for me: 1 tsp baking soda, 1 teaspoon Neem oil (I found it effective only if azadirachtin is listed as active ingredient), a few drops of Bonner's liquid soap, 1 quart water. (These measures can be rescaled for a 1 gallon bottle or larger sizes.) Mix all with little water first and then add to a spray bottle with the remaining water. All leaves and stems should be sprayed well. After this happened to my plants, as a prevention, I now spray them with diluted baking soda and/or neem oil every couple of weeks and have not had any powdery mildew problems since then. I also moved the phloxes to another location for better air circulation. For shrubs, pruning them right would achieve the same.

If you prefer chemical treatment, then someone else would be of more help.

Thank you. I do have neem oil. Will Dawn liquid work instead of Bonner's?

Yes, any liquid soap should be fine. Please check that azadirachtin is listed on the ingredient list on your neem oil. I use Dyna-Pro.

Very common on Euonymus kiautschovicus 'Manhattan'

Will Dawn liquid work i

==>>> that is a dish DETERGENT .. not a horticultural soap ... detergents are never recommended ...

i completely ignore powdery mildew ... except to open up the plant thru proper pruning ... it ebbs and flows over the years ... full fall clean up is also helpful ...

it has little or no effect on most plants... except in extreme situations.. and your pix dont show that ...

ken

btw .. my opinion is in regard to my MI ... where summers are very hot ...

knowing where you are.. would really help .. as i am sure it could be a much larger problem in more humid hot areas.. like the south .. and PNW ..

please always add your location ...

ken

ken- Zone 7a

And thank you so much for the help. I hadn't pruned in 2 years and these shrubs get so dense! I'll take a pic of the manicure!

mimipadv, my advice is to check with your local extension office about what to do with the powdery mildew. We don't have any major humidity problems here and, when I had powdery mildew on my plants, I contacted our local extension office and was given the same advice I wrote to you, that is, to spray it and also increase the air circulation. My local extension office is Cornell, also known nationally, and they were quite receptive to my preference for the organic approach, including homemade sprays. As for Dawn liquid soap, I really don't use it to know the ingredients. Dr. Bronner's liquid soap is not detergent-based and would not have any harmful effects. Baking soda and/or 100% neem oil are more important than a few drops of the liquid soap anyway. Hope this helps.