An Easy DIY Natural Fungicide for Plants

Use this homemade natural fungicide for plants to treat powdery mildew and other fungal issues around the garden.

Plants in the cucurbit family like pumpkins, squash, and watermelon are prone to developing powdery mildew. (The Grow Network)

An Easy DIY Natural Fungicide for Plants

If you’re growing any gourds this year, this easy homemade fungicide recipe might just come in handy for you. Cucurbits like cucumbers, squash, pumpkins, and watermelon are notoriously prone to a fungal disease known as powdery mildew.

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As you’ll see below, this simple fungicide for plants can be used to treat other fungus issues around the garden as well. It is also widely used by rose aficionados to help control the black spot fungus that is a common problem for rose bushes.

Is Powdery Mildew Consuming Your Cucumbers?

A natural fungicide can treat the powdery mildew evident on this cucumber plant. (The Grow Network)

Powdery mildew is easily recognizable in an otherwise healthy garden. When this fungus goes unchecked, it often looks like someone has used a flour sifter to apply a thin coat of flour across the leaves of affected plants.

Powdery mildew can pop up on other garden plants too. Some other plants that are especially prone to this fungal issue include phlox, bee balm, roses, apples, and grapes.

Make Your Own Homemade Fungicide for Plants

Use this recipe as a homemade fungicide for plants. (The Grow Network)

This basic recipe originally came from The Natural Gardener in Austin.


4 level tsp. or 1-1/3 tbsp. of baking soda
1 teaspoon of mild soap (e.g., Dawn or Ivory—should be biodegradable with no phosphates)
1 gallon of water


Mix all ingredients thoroughly and keep agitated. Then spray plants. Spray all leaves thoroughly until the solution begins to run off.  Spray the top and bottom of affected leaves and all of the small new leaves, even if they don’t appear to have the fungus yet.

Peer Reviewed and Scientist Approved

Gardeners might be infamous for passing along myths and legends, but this DIY natural fungicide has some pretty good academic credentials. Dr. R. Kenneth Horst from Cornell University led a series of studies to document the effectiveness of baking soda as a fungicide.

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His studies found that a 0.5% solution of baking soda is best to control powdery mildew in cucurbits, and he found that using a surfactant (like soap or horticultural oil) is necessary to make the solution effective.1)http://www.attra.org/attra-pub/bakingsoda.html You can find lots of information about Dr. Horst’s work and other relevant research in this document from the National Center for Appropriate Technology:

View or Download This Resource Here: “Use of Baking Soda as a Fungicide”

First Steps to Controlling Fungal Issues

As a first step in preventing fungus, make sure you are irrigating properly. (The Grow Network)

Image by 1239652 from Pixabay

Before you start breaking out the natural fungicide, consider whether or not you might be able to control the issue with some other “natural” measures.

Watch Your Water

For example, did you know that you may be able to fight fungus simply by adjusting your watering schedule? Powdery mildew can spring up during exceptionally dry conditions, especially when you have hot, dry days and cool nights. If you are growing plants that are susceptible to drought stress, make sure that they are getting regular water during summer hot streaks.

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Circulate the News

Air circulation is one of the biggest factors in many fungal infections, and you might be able to control powdery mildew and other fungal issues by spacing plants farther apart and pruning selectively to increase air flow through the affected area.2)The Organic Gardener’s Handbook of Natural Pest and Disease Control. Ellis, Barbara W. and Martin, Deborah L. 2009. Rodale.

Join the Resistance

And if you’ve had problems with powdery mildew in the past, one of the best things you can do is be sure to select plants that are resistant to powdery mildew in the future. Some varieties are less susceptible to the fungus, and they are advertised as being resistant in seed catalogs and garden centers.

What Do You Think?

Do you have a favorite fungicide for plants that you use in your garden? Do you have your own recipe for homemade fungicide? Let us know in the comments below!


This article was originally published on May 17, 2016. The author may not currently be available to respond to comments; however, we encourage our Community members to chime in to share their experiences and answer questions!

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1 http://www.attra.org/attra-pub/bakingsoda.html
2 The Organic Gardener’s Handbook of Natural Pest and Disease Control. Ellis, Barbara W. and Martin, Deborah L. 2009. Rodale.
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  • Softballumpire says:

    I am confused, you use the term mild soap then mention Ivory & Dawn. Ivory and Dawn come in mild liquid dish detergent. Ivory also makes soap flakes or Ivory bar soap can be easily grated like cheese. Off hand, I am not familiar with Dawn soap so the term soap and detergent could be being used synonymously or erroneously. I am familiar with Fels Naptha soap which may not be classified as gentle. Then there is the Boraxo hand soap in powdered granules which also may not qualify as gentle.

    If soap is to be used exclusively, castille soap is mild, how does it impact the efficacy?

  • This is a very interesting and might be useful right away. Does this recipe also drive away ants? Ants are attacking my peppers, tomatoes and eggplants. The peppers appearances are now very bad with leaves curling because of the ants.

    And, one more question, is the mild soap a liquid soap or bar?

    1. Ants are a symptom of the “real” problem. When you see ants marching, take this as a warning, you have pests like APHIDS, which DO suck the sap from a plant. Causing it to shrivel and curl. Ants are there for the “honey” the aphids secrete.

    2. Sandy says:

      The ants are FARMING the aphids. A simple, simple remedy I have used for years is to sprinkle a few handfuls of homemade compost around the base of the invaded plant. You can gently stir the surface a little to help it get to their root systems. By the next day the aphids and the ants will have vanished. WHY?? What I assumed when this worked for me is that something about the nutrients balances and enhances the biochemistry of the plant. Most of my experiences are with curcubits and brassicas, but I have used this with other fruiting plants and leafy greens. It also worked on my dwarf cherry tree this summer (note to self: Use more compost more often on my fruit trees). I just listened to a brief seminar from Elaine Ingram on the Living Soil Web. She explained, among many other points, how helpful soil microorganisms are in moving nutriennts through a plant’s root systems into the plant. I had already understood that soil microorganisms help breakdown composted plant material and mineral components as your pile turns into compost. This experience brought home to me the oft cited comment that bugs tend not to bother healthy organic plants.

  • norman says:

    what is good for preventing worms in apples?

  • Debra says:

    Why would you not use a small amount of Castille liquid soap instead? Seems a better choice to me. When they mention “horticultural oil” what are they talking about – neem oil or something of that nature?

  • d. henry Lee says:

    I will try it.

  • Maury says:

    Please make your posts “pinnable” to Pinterest. I often want to to save an idea of yours to my garden tips board (like this one).

  • Isobelle says:

    Thank you for the Garden Fungicide recipe. I have struggled with this very thing for a few years.
    It appears on any squash type plant as well as on my tomato plant leaves. I look forward to using this just as soon as I can get some mixed.

  • Gay says:

    I have used raw whey from clabbering milk with great success for fungus. This recipe will be good to have for when I don’t have raw milk on hand. Thank you!

  • Bill P says:

    Elaine Ingham’s The Compost Tea Brewing Manual points out that compost tea has been instrumental in preventing the appearance of psychedelic mushrooms where they are unwelcome. It’s wonderful stuff with a great many uses.

  • Thank God you posted this info! I have struggled for years with this stuff on my squash and I’m definitely printing this out to try next year. I sure hope it will work for me!

  • Dr M.DonAvidfz says:

    I really appreciated and thank Almighty God so well for this released of imapActation to us ward for a better one growth.

  • Al Crockett says:

    will this work no tomato plants to treat blight?

    1. JC says:

      Baking soda does not work well as a fungicide on tomatoes you need to use something that has copper or magnesium in it

  • WvPSy says:

    786177 255347 There is noticeably a bundle to know about this. I assume you created certain nice points in functions also. 307940

  • Jenn says:

    A few alternatives to using baking soda – hydrogen peroxide, crushed aspirins (salicylic acid), mild bleach solution – 1 part bleach to 9 parts water – FYI the chlorine bleach degrades and evaporates very quickly, does not remain or build up in your soil

  • Enosencia says:

    will this work on watermelons?

  • gennywu says:

    My mom used this recipe in her garden for over 50 years and she never needed to use any other fungicide. She always used soap in the form of dish detergent. It is simple, effective and always available. I have now adopted her practice in my garden. Glad to read about it in this article.

  • Lisa Petrillo says:

    I use a combo of castille soap and vegetable oil with the baking soda. I have used it with success against blight on my tomatoes as well, as long as it was just starting.

  • herbantherapy says:

    @softballumpire You must use a liquid soap as this acts as the surfactant (or the thing that makes it all stick to the surface of the leaves and doesn’t just immediately run off the plant). Using bar soap flakes will not make the solution stick to the plant unless you turn the bar soap into liquid first and then make the anti fungal solution with the liquid soap.
    @debra using Castile liquid soap soap works just as well as dawn.Typically horticulture oil is neem but can sometimes be combinations including neem and tea tree oil or other variations. If you have neem on hand that works just fine.

  • MissPatricia says:

    For Maury: You can save the post on Pinterest by clicking on ‘SAVE’ in the upper left-hand corner. Otherwise, it is short enough to write it out on a card to keep.

  • MissPatricia says:

    Also, if anyone has an answer to what to do about worms and spots in apples, I would appreciate it. I used a thick mulch of wood chips under my apple trees as Paul Gautschi teaches. That did improve the quality of my apples, which, by the way, taste about ten times better than apples bought in the store, but many of my apples have rust-colored spots.

    1. Owl says:

      I use a product called Tanglefoot barrier for worms in my fruit and nut trees with excellent results. It doesn’t look very pretty but it makes a huge difference in losses.

  • dd74804 says:

    Years ago I used powdered milk for powdery mildew and it stopped it with one application. I’ve never had it since, maybe because I learned to prune overcrowded plants. ‘;D

  • tanyalaird says:

    One part organic milk mixed with 10 parts water is recommended by Gardening Asutralia https://www.abc.net.au/gardening/factsheets/organic-fungicide/9426514

  • harpiano says:

    Wow! FINALLY a remedy! Just yesterday I was looking at my kombucha winter squash, thinking I guess I’ll pull this out when the 2 squash are mature enough to pick because the powdery mildew had just showed up. During the “winter” in Hawaii when its wetter and cooler, the stuff just appears everywhere! I’m so excited because I love growing cucumbers and lately they just don’t make it due to the powdery mildew.

    1. harpiano says:

      I wonder if the whey from organic milk will be as effective as organic milk sprayed on plants? @tanyalaird

  • kristenlee429 says:

    I tried this recipe last year, but I also added about 20 drops of tea tree oil to a gallon of mixture. It is a fungicide, and I believe the smell also kept the squirrels (who kept trying to eat my pumpkins) away. Don’t forget to spray your plants when the sun is NOT blazing on them, so you don’t burn the leaves.

  • pbandjellyyy says:

    I wonder if this works on Hollyhock rust.

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