Sumo Gardener

How to Use Potassium Bicarbonate for Powdery Mildew

Are you wondering on how you can organically get rid of powdery mildew? Have you heard about using potassium bicarbonate for powdery mildew?

Get to know more about it and how you can prevent this powdery mildew from invading your plants again.


How to Use Potassium Bicarbonate for Powdery Mildew

More and more people are having problems with the appearance of their plants, especially during the summer season. One of the most common diseases that can be found is the powdery mildew which makes the leaves looks ugly. 

The problem is, it does not only make the look ugly but can ruin the entire plant in the long run. This is the reason why people are looking for ways on how to get rid and prevent this problem from happening.

What is Powdery Mildew?

What is Powdery Mildew?

One of the plant diseases that is most commonly seen today is the powdery mildew. The good thing about this white fungus on plants is that it can easily be spot on because the fungus will start forming a gray or white powdery film on the fruit, stems, and the leaves of the plants.

It is known as a fungal disease that is caused by different types of the fungi, which then belongs to the Erysiphales. Powdery mildew thrives in the humid and warm environment, and as well as in overwinters It is typically spread by insects or the wind.

Due to this plant problem, more and more garden owners are looking for ways on how they can organically get rid of this powdery mildew.

One of the most organic ways on how you can get rid of this mildew is by using potassium bicarbonate. Get to know the wonder of treating powdery mildew using potassium bicarbonate by reading the information below.

Advanced Stage of Powdery Mildew

Advanced Stage of Powdery Mildew

When the plants’ leaves turn into yellow or brown and start curling, then this just means that the disease is already in the advance stage.

This will make the plant to prematurely defoliate. On trees and plants that produce flowers, this white fungus on plants can instantly lead to early dropping of the bud or reduce the quality of the flower.

Controlling Powdery Mildew from Advancing

Controlling powdery mildew from advancing and entirely ruin your plant is essential. The best way to do this is to detect it as early as possible. Different products can help you with controlling and eliminating the problem at hand.

Most of the products contain chemicals, which is why people are looking for different ways on how they can kill the powdery mildew without using chemicals.

Fortunately, there are now organic ways to do that, and one is with the use of potassium bicarbonate, which has proven to be efficient and safe.

Potassium Bicarbonate Solution to Remove Powdery Mildew

Potassium bicarbonate is often one of the active ingredients that can help kill powdery mildew. It has been using as a fungicide and is not a new idea to the industry. This solution is made out of a gallon of water and an ounce of potassium bicarbonate.

Nowadays, people are incorporating potassium bicarbonate for plants infested with powdery mildew, and some are even adding other ingredients to make the solution more efficient.

Potassium Bicarbonate (1 lb) Eco-Friendly Packaging

If you are having problems with powdery mildew, then knowing how you can make a potassium bicarbonate solution is essential. There are different solutions that you can do and choose the best one that is most convenient for you is important.

1. Milk + Potassium Bicarbonate

The ingredients that you will need for this are a cup of cow’s milk, 3 cups of water and a pinch of potassium bicarbonate.

Start mixing all of the ingredients and pour it in bottle spray. Before spraying it, make sure to shake the bottle to combine all the ingredients equally. This solution is perfect for squats and rose leaves.

2. Watery Cow's Milk + Soap + Potassium Bicarbonate

The ingredients that you will need here are a couple of cups of watery cow’s milk, water, 3/4 teaspoon of soap, preferably non-detergent one and a teaspoon of potassium bicarbonate.

Mix all of the ingredients and pour it in a bottle spray. Shake well before using it and make sure to spray it regularly on plants. If it rains then reapplication is needed.

Potassium Bicarbonate Solution to Remove Powdery Mildew

3. Dishwashing Liquid + Vegetable Oil + Potassium Bicarbonate

The ingredients that you will need is a tablespoon of dishwashing liquid, vegetable oil, potassium bicarbonate, and a gallon of water.

Mix all ingredients and pour it in a bottle spray. Before using the solution, it would be best to shake it for the solution to be combined thoroughly.

When spraying, make sure to include the leaves’ underside as well. Avoid spraying during sunny or hot days as this can cause the leaves to be burnt.

4. Liquid Soap + Vegetable Oil + Potassium Bicarbonate

The ingredients that you will need is a gallon of water, half a teaspoon of liquid soap, a tablespoon of vegetable oil, and a tablespoon of potassium bicarbonate.

Mix all the ingredients and pour them in a bottle spray. Of course, you will need to shake it before spraying the solution to the plants.

How to Apply Potassium Bicarbonate Solutions for Powdery Mildew Affected Plants

Typically, it is ideal to thoroughly spray the entire sides of the plant’s leaves, including the buds and the stems to ensure that they are free of powdery mildew.

It would also be best to spray the leaves which are dealing with diseases every single week. Spraying once every 2 weeks will do to help prevent the powdery mildew from developing again.

Also read: How to Use Vinegar for Pest Control

Wrapping Up Natural Solution for Treating Powdery Mildew with Potassium Bicarbonate

These are all the potassium bicarbonate solutions that you may do from the comfort of your home to keep your plants protected and for you to be able to get rid of the powdery mildew problem that’s been invading your lovely plants.

If you are one of the many who’s been having powdery mildew problems, then the tips above will surely help you get rid of it.  

Just follow one of the 4 potassium bicarbonate solution recipes, and your garden will surely be on its way to being free of powdery mildew.

About the Author Ann Katelyn

I'm Ann Katelyn, Creator and Chief Author of Sumo Gardener. Since I was a child I've always been fascinated with plants and gardens, and as an adult this has developed into my most loved hobby. I have dedicated most of my life to gardening and started Sumo Gardener as a way to express my knowledge about gardening with the hope of helping other people's gardens thrive.

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Leave a Comment:

Mike says August 1, 2018

We used formula #2 above because it gave the combined milk and potassium bicarb with dish washing fluid combination and provided correct volumes to go by. Wear gloves during treatment or you’ll get some yellowing of your fingers and hands.

We made the mistakes of planting purchased acorn squash which brought the powdery mildew into our garden. We planted too close to watermelon and cucumbers which allowed transfer and we failed to get the plants up off the ground soon enough and watered from above at night, all big mistakes in a first round learning curve.

Watch out for suggestions to use 3% hydrogen peroxide. It seems to migrate into the leaf tissues and affected the watermelon in serious ways.

James says October 10, 2020

Thanks for the tips.

I mistakenly bought some potassium carbonate instead of bicarbonate to deal with powdery mildew on grass… Would it be suitable as well but may need to be diluted with more water? If I understand correctly, we would need carbon dioxide to convert the carbonate to bicarbonate but not sure how to go about it or whether that’s needed.

    Ann Katelyn says October 12, 2020

    Hey James, thanks for your question!

    Shopping mishaps – we’ve all been here! Unfortunately, there’s no simple way to change your potassium carbonate into potassium bicarbonate, and it’s not much use around the house either unless you enjoy making your own soaps. It won’t address your powdery mildew problem even if it’s diluted, so it’s best to return the product if possible and purchase the potassium bicarbonate.

    We hope that answered your question.

    Thanks Ann

      James says October 12, 2020

      Oh shoot… guess we’ll be making some soap then!

      I’m curious as to the science behind why carbonate is not effective vs. bicarbonate to effectively treat PM, if you know.


Irene Clemente says February 25, 2021

Actually, I have a question. Can I treat the soil with potassium bicarbonate solution prior to planting seeds? I gad powdery mildew on my pumpkins and zucchini

    Ann says March 1, 2021


    Thank you so much for your question! While you certainly can treat the soil with your bicarbonate solution prior to planting seeds (as this will not harm your plants), the spores generally travel by air and land on the plant’s leaves.

    So, while preparing the soil beforehand will be helpful in terms of getting rid of any spores left in the soil, you will still have to keep an eye out for new spores that drift onto your plants and regularly spray them with the bicarbonate solution to minimize any powdery mildew infections in their early stages.

    We hope that answers your question!

    The Sumo Team

Claudia Dieter says July 23, 2021

I purchased some lye water at an Asian grocery. Potassium carbonate and sodium bicarbonate. Can I use this for powdery mildew? If so, what proportions? Thanks.

ANDREA says February 12, 2022

Thank you for the tips. Could you post the portions (or proportions) needed for #3 please?
Thanks so much!

    Mabel Vasquez says February 20, 2022

    Hi Andrea,

    1 tablespoon of each works brilliantly as a general treatment

    – Dishwashing Liquid, 1 tablespoon
    – Vegetable Oil, 1 tablespoon
    – Potassium Bicarbonate, 1 tablespoon
    – Water, 1 gallon

    You can add an extra spoon of dish soap if there is an insect infestation as well as mildew.

    Good luck!

    Kind regards,

    Mabel Vasquez – Horticulturalist

Belinda says June 21, 2023

Can a gallon of solution be mixed and then stored in the fridge for further use?

    Mabel Vasquez says June 29, 2023

    Hi Belinda,

    If you’re using milk in the solution, it’ll keep for as long as the milk will – so I wouldn’t leave it in too long. If you leave milk out the solution would store for longer, but as I understand it, potassium bicarbonate will only break down in water if it’s heated.

    Best regards,

    Mabel Vasquez – Horticulturalist

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