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Powdery Mildew

18 years ago

Reporting back on a previous topic... I think it was Sierra posted awhile back to use baking soda and water to control Powdery Mildew (of which there is a LOT this year!) and I said maybe not on roses due to sodium content.

Since then I found a recommendation for exactly that on the ARS website so I figured it must be safe and gave it a shot. It is working GREAT so far. Even after being washed off in 2 hours by a thunderstorm. I reapplied it the next day just in case. Roses and delphiniums responding well so far.

The solution is:

16 oz spray bottle

1/8 tsp baking soda

few drops of dishsoap

fill with water

There's also the milk and water method which I have not tried but I hear is effective.

Comments (15)

  • 18 years ago

    I tried the milk and it worked on the mini roses very well. It worked on the delph a bit....but either I missed a few spots or it didn't do very well on the bottom leaves.Or maybe it just needs another application because it got washed off so quickly.

    We have had so much rain and so many thunder storms that I am not sure much is helping right now. Last night I went out shopping for about an hour....when I came home there was this white stuff all over the yard.....on closer inspection it was hail.....the size of large peas. It was only raining in town no hail.....but up here.....OHHHHHHHHHH!!!! Many of the plants were beaten up pretty badly. Plus they were sitting in this ice still....not much I could do about it. The strawberries were pretty much ruined...beaten off the vine...even the ornaments on the fence are damaged and some were shattered. I put the cannas that were in pots in the shed, just incase it wasn't finished....their poor leaves were already ripped to shreds. :-(

    Sorry off topic....I plan on trying the milk again...well if it ever stops raining and storming. Another thunder storm forcast for today.

    The milk recipe is..

    1/3 whole milk

    2/3 water

    I used a one litre spray bottle.


  • 18 years ago

    Is the fat content of the milk important?

  • 18 years ago

    I wondered that about the milk too - that's why I tried the baking soda instead. I only buy skim milk.

    Sierra I'm so sorry to hear about your hail damage. On the bright side you might be surprised to see that some plants recover quickly from hail, or so I have heard a number of times. Hope so!

  • 18 years ago

    Sierra - where did you find that milk/water 'recipe' for powdery mildew? 30% milk seems very high.

    Skim milk is fine.

    Link below covers the topic well.

    Here is a link that might be useful: milk and mildew

  • 18 years ago

    Would this work on peas, too?


  • 18 years ago

    Yes, it will work on peas or anything else with powdery mildew.

  • 18 years ago

    Jan thanks for the article. What milk/water ratio is usually recommended? Shauna I have never treated PM on vegetables prior to this because I don't like chemicals in the food, but this will be great for peas - mine usually get wiped out July by PM.

  • 18 years ago

    Good morning folks,

    I found the milk recipe on the said to definately use whole milk as it worked best. I assume that it works better because of the fat content.....perhaps it sticks to the leaves better. I don't use whole milk either, so I went and bought a litre. As I said, it worked on the mini if it ain't broke don't fix I will continue to use the whole milk at 1/3. If you try the skimmed milk and it back and let us all know.

    I'd far rather purchase a litre of whole milk than a litre of some chemical for this mildew problem.

    Just relaying what has worked for me.

  • 18 years ago

    I'll "sacrifice" one row of peas to test both methods. This row all germinated really evenly and I can easily do half the row in milk and half in the baking soda. I'll be using 2% milk. It sounds like both methods work fine. But let's find out if one is better than the other side by side. I'll let you know come mid Aug. when my peas are usually covered with the stuff and I'm sneezing like mad. (Makes my arms itchy, too)


  • 18 years ago

    It is interesting that most of the research on the milk has been done in Australia. Some now is going on in California among the grape growers. If it works like a wonder cure....sure is a nice safe way to zap powdery mildew. You are so right...makes a person feel a whole bunch better spraying foodstuff with milk or baking soda than with something that has a skull and crossbones on its label!

    The above link and other sources I googled indicate a 10% solution of milk. But I didn't read a lot of the google results....just four or five. 10% would be one part milk to 9 parts water. Sierra came across a 30% recipe. The only thing I found at 30% was when using Whey. Yup, they found milk by-products to be effective too. Interesting stuff. I wonder if milk would work on Black Spot on Roses?
    Here is another link....

    Here is a link that might be useful: more on milk and PM

  • 18 years ago

    There may be other reasons, but I'm guessing that the lactoferrin in milk is what causes the milk to act as a fungicide. Based on that, I think it might work on black spot too.

    Here is a link that might be useful: What is lactoferrin?

  • 18 years ago

    I've wondered recently if the reason that milk and corn meal work against fungal diseases it that they promote the growth of a beneficial fungus that either out competes the powdery mildew or acts symbiotically with the plant to help resist fungal diseases. A while back I went to a talk called "'shrooms in the hood: Urban fungus, the good, the bad and the ugly". The man speaking talked about the symbiotic relationship between trees and mushrooms and showed data on how much better the trees with the mushrooms grew. He also talked about other symbiotic fungus that helped plants. It started me wondering about the corn meal/milk method. There may be nothing to my theroy, but it's an interesting thought.


  • 18 years ago

    Bella, your reasoning has much merit. The theory behind cornmeal controlling Blackspot is that cornmeal does promote the growth of 'good fungus'. I have not found cornmeal to be particularly effective against black spot. But some swear by it. Next time I face black spot, I am going to try milk.

    As previously stated by spartangardener, milk's fungicidal properties could be what combats PM. But it also could be as simple as milk changes the PH on the leaf Baking Soda does. PM can exist only in a narrow range of PH so anything that changes it will inhibit the mildew growth. Vinegar, lemon juice and other acids might work? And don't forget the Listerine!


  • 12 years ago

    I use the 10 to one ratio when using no fat milk and water, I believe it works better for me than baking soda and I use both in my Aquaponic beds. I had PM bad and this is clearing it all up without polluting the water and fish, plus the calcium is good for the fish, but the soap and soda.mmm not so much. :-)

    Here is a link that might be useful: Eden Aquaponics

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