Just to reinforce what Bil has already written, while Powdery Mildew does have its optomal growth when the weather is warm and humid that does not mean it will not grow at other times and under other circumstances.
I have had good success using a 50/50 mix of fat free milk and water to control PM

Here is a link that might be useful: Powdery Mildew

Bil1me,
How well does the 2.5 tblspoons of oil, mix in the water?

Not well at all, but that makes it stick to the plant. You need a nozzle on your sprayer that won't clog up with the baking soda, and shake it like Helga.

I assume you're talking about last season? Even with the best conditions, cucurbits generally succumb at the end of the season. By then, I'm so tired of zucchini it comes as a great relief!
I find keeping cucurbits very well watered and mulched in very well-composted soil holds off pm.
I'm pretty sure, despite what you'd think about fungi thriving in high humidity, pm tends to take hold when plants are weakend by dry conditions.
I'm spraying my cucurbits with foliar fertilisers and they still look really healthy, with no pm. Usually by now it would be showing up.

feijoas, I have talked with a number of people, over the years, about Powdery Mildew and it is one difficult to control plant disease. Some of these people, myself included, seem to have some success controling PM by periodically hosing susceptible plants down. That seems to wash off any of the PM spores. I realize this is contrary to what many advise on the thought that hosing tghe leaves down would increase the humidity around them and therefore make conditions for PM better. But if washing your hands helps prevent disease transmission for you why would not the same thing, kind of, not do the same for your plants?

g'day SV,

for me i get powdery mildew mostly only when the plant is coming to the end of its productive life, at that stage i see it as the plant is running short of resources, like old age in human's.

we have a milk recipe on our remedies page:

also i plant PM susceptible plants in well drained soil and in a breezy position lots of air movement to keep foliage dry, never water over the foliage just around the roots.

when we get PM it starts with the oldest leaves but eventually brings about the finish of the plant.

len

Here is a link that might be useful: lens remedies page

I agree. Even with plants that are relatively close, the older ones seem vulnerable while the younger ones are still impervious.

I have read that PM survives in the soil. I live in southern Oregon on the coast, lots of fog. I have used the baking soda and water and am having great luck with that on my zucchini plants. I have a small garden but I do rotate the "crops" each year. How do I make sure the PM is no longer in the soil?

The spores that cause Powdery Mildew need plant debris to exist, so they may live on any plant debris in the soil but they will not survive in just soil.

Here is a link that might be useful: About Powdery Mildew

I have a Banana plant I did not want to lose to powdery mildew... I saw that it had started to grow on the soil (visible area). At first sight of infestation, I took a 32oz. spray bottle and filled it with reverse osmosis water, added 5-10 drops each of pure purification oil, pure lemon oil, and pure frankincense oil. Shake vigorously before each application, inverting the bottle, etc. All oils were from Young Living essential oils, only because my wife had them around and they smell wonderful. I misted the entire plant (foliage and all), I also soaked (via mist) the entire visible sphagnum peat surface area of the pot. Problem solved, 2-3 days later, no visible trace of the powdery mildew. I have continued the tincture for two to three weeks without any visible return of powdery mildew. The plant is looking vigorous and healthy. In the future I will also add 5-10 drops of pure oil of oregano and pure cinnamon oil to the mix, as they are known to be anti-fungal and anti-microbial agents. Their use dates back to the time of Hippocrates.

The purification oil consists of the following...Citronella (Cymbopogon nardus), lemongrass (Cymbopogon flexuosus), rosemary (Rosmarinus officinalis), Melaleuca (Melaleuca alternifolia) lavandin (Lavandula x hybrida), and myrtle (Myrtus communis).

Anyway, I hope my little experiment helps you all. I keep my banana plant indoors, so there was no rain to wash off the water/oil mixture. I would imagine this would make a huge difference into the efficacy of the treatment. All the best!

-Chris

tidalturf,

Hope you check back to learn that powdery mildew does *not* grow on soil.

HELP. MILDEW ON EVERYTHING,,,has killed zinnias , all over roses and now is killing my gourds and pumpkins. Everything I have read about treating soil ..as that is what everyone says is the problem..its in the soil now.. Does not tell me what to do when garden full of established plants ..mainly roses. I have tried the copper spray which is what garden center suggested. Did not help at all. Literally on EVERYTHING and has been for several years now. Completely killed all of my sweet peas. A real mess and don't want to remove my roses. Some r 40 years old. HELP!,, please.

Copper fungicides are pretty strong things to use and following common organic growing and Integrated Pest Management techniques is probably the product of last resort. to use.

I have had good results using a mixture of 1 teaspoon of Baking Soda mixed in 1 quart of water, or 3 tablespoons in 1 gallon of water, or a 50/50 mixture of fat free milk and water. Some people have added a drop or two of vegetable oil to the Baking Soda mix to help it stick, but I have not found that necessary.

Perhaps this article might be of some help.

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7493.html

kimmq is kimmsr

I ordered something called Mildew Cure this year. It is oil based. I have every other disease in the garden this year but PM. It does not carry over in soil so I even compost peas and zukes that get it by the end with no ill effect.

Powdery mildew is NOT in the soil.

It spreads on the air.

I am growing begonia in big pots and PM before. Now I am mulching it with horsetail. No PM anymore. This year I am planning to get horsetail and cover all beds where cucurbits will grow next year.

We grow a lot of winter squash, and inevitably, when mid-August rolls around, I start getting powdery mildew, and its a race to see if the fruit matures or the plants die. This year I tried spraying Safer sulfur solution when the mildew first showed up, repeated it twice at one week intervals, and I got another month of non-diseased plants. Picked 60 fully mature squash, twice the normal yield.

I've had a terrible time here in L.A.- zone 10- with powdery mildew - this time it got my squash, cucumbers, tomatoes and bush beans; now it's working on my pumpkins.

I have tried a bunch of things - milk, baking soda and a little detergent, etc.- but they seem not to work. Realize I probably water too late in the day and put manure on at the wrong time...but still!

Most sites states that "treating the soil" is not useful, but one site says to cover with clear plastic and let it sit for 4-6 weeks - longer if it's rainy. Seems like a long time to wait - but I'd do anything to fix this problem!

Can anyone help?

Another thing - I'm from the South and can't help but notice how much better plants like melons, okra, summer squashes do there. I'd attribute this to it nearly always dropping down to the 50's and 60's at night, instead of staying hot.

Am I the only one that thinks this?

I've found a new company that offers a great product. It's called Bioxy USA and they sell Bioxy Plus which is a green, all natural fungicide. We have a huge tropical garden in our backyard and I use Bioxy Plus all the time. I have totally eliminated powdery mildew on all our plants. Worth a try if what you have already tried doesn't work. I use it weekly so I won't have any reoccurance.

Do you work for the company, jmcaspar? Can you show the forum some information that this product is safe for plants. A product label would be helpful.

Bioxy Plus does not appear to be listed for use in gardens for any reason, anywhere. Therefore the product would not be acceptable for use by any organic grower.

kimmq is kimmsr

Bioxy Plus is peracetic acid. When mixed with water, it breaks down into hydrogen peroxide and acetic acid. Hydrogen peroxide is recognized as having anitfungal properties and is an acceptable organic treatment.

Bioxy Plus is not listed for use in gardens and is not then acceptable for use by any gardener much less an organic grower.

kimmq is kimmsr

Is the soi conta contaminated ?

Please reread the entire thread. Powdery mildew cannot subsist in just garden soil. Or container soil. It must have plant tissue to survive so if you practice good garden sanitation and clear your beds at the end of the season of weeds and any plant debris. then there should be minimal concern about it carrying over after winter. An end of season mulch will help as well.