Powdery mildew is the scourge of my garden.

[sanzfrancisco]

I had a lovely garden for much of the summer, (photos below.) Then the powdery mildew started. It never stopped. I used fungicide, and potassium bicarbonate solution; three different recipes. Nothing helped, and many of my plants are gone.
What I'd like to know is, how do I treat the soil before I plant anything else? Powdery mildew leaves spores, right?
Thanks,
janice

 

[Chuck]

Powdery mildew (pm) is mainly spread by the wind from plant to plant. Pm spores are on left over debris from infected plants and can survive overwintering on these debris. The spores do not live in the soil, they live on the soil on debris. Plants are much more susceptible when they are grown too close together and cannot get enough air circulation and/or sunlight to all parts of the plant. Pm likes a warm dry humid habitat and the lack of air circulation. Pm does not survive well in sunny locations and plants being too close together forms a shady humid environment thus encouraging pm. Baking soda works to a limited degree but potassium bicarbonate is what you really want to use. It kills the spores very quickly no matter if they are on the plant or on the soil. Remove ALL plant debris AND mulch if you contract pm at any time during the year.

 

[YumYum]

Potassium bicarbonate is what you really want to use. It kills the spores very quickly no matter if they are on the plant or on the soil.

Where do you aquire this and what is the procedure and dose? What I mean is it something you can get in the cooking aisle at the grocery store?

 

[DirtMechanic]

Amazon for one place

Mono- and di-potassium salts of phosphorous acid are its big brother. Also organic. Search for a product named agri-fos. I think montery makes it now..

 

[YumYum]

I was hoping it was disquised as something I could just go to town and buy but I cant find any such thing. Im not much for online ordering if I can help it.

As a matter of fact I have some powdery mildew on a few of my cucumber leaves despite me spraying chlorantholanil weekly. Nothing major but still I like to broaden my horizon.

 

[DirtMechanic]

You can use the silicone hydro nutrients in a spray form. It has a waxlike property and is rain and heat resistant. Anything to put a layer between the fungi and its target surface. Fungi have no teeth. The way they bite in is chemically enzymatic. Thus any layer between a spore and leaf surface works to the purpose. You just don't want to suffocate or burn the plant tissue. Some chemicals stop their enzymes. Mineral oil is used as horticultural oil because its crap for being a oil that plates up and lubricates. In short it breathes oxygen. They put mineral oil on babies and trees to stop fungus because it allows the skin to breathe while being a protective layer. Even these sodium and potassium bicarbonate cures are a layer, but while they go on wet, they then dry to a fine powder coating. Perhaps you too can dust your plants? Once I got into aspirin and water for this same purpose and was amazed to see how 4 puny dissolved aspirin in a gallon of water could make an acidic powder that covered so many plants!

 

[sanzfrancisco]

Powdery mildew (pm) is mainly spread by the wind from plant to plant. Pm spores are on left over debris from infected plants and can survive overwintering on these debris. The spores do not live in the soil, they live on the soil on debris. Plants are much more susceptible when they are grown too close together and cannot get enough air circulation and/or sunlight to all parts of the plant. Pm likes a warm dry humid habitat and the lack of air circulation. Pm does not survive well in sunny locations and plants being too close together forms a shady humid environment thus encouraging pm. Baking soda works to a limited degree but potassium bicarbonate is what you really want to use. It kills the spores very quickly no matter if they are on the plant or on the soil. Remove ALL plant debris AND mulch if you contract pm at any time during the year.

Thanks so much for the reply, Chuck. I remove all the plant debris from the soil, often using barbeque tongs for things that are hard to reach. My flowers weren't planted close together, but they grew that way. The did get lots of direct sun. Potassium bicarbonate did not work at all, so I'm a bit frustrated. Good to know I don't have to treat the soil. Thanks again.
janice