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How to Make a Fungicide Using Copper Sulfate Crystals

Written by Naomi Meza


Posted on July 08 2022

Are you concerned about the chemicals in conventional fungicides and want to take a more natural approach to protect your plants?

You can make your fungicide using copper sulfate crystals, calcium hydroxide, and water.

This mixture is called the Bordeaux mixture and has been used for years to control fungal diseases on vegetables, fruits, ornamentals, and turf.


Related Post: A Guide to Natural Herbicides, Pesticides and Fungicides for Your Garden


It is a safe and effective way to treat diseases such as black spots, powdery mildew, and rust.

Copper ions in the Bordeaux mixture are deadly to fungi but have no effect on plants.

Bordeaux mixture suffocates the fungus and prevents it from growing and reproducing.

It is most effective when applied before the disease appears but is still effective when applied to early signs of disease.

Before going through the step-by-step process of how to make a copper fungicide, let's look at what a fungicide is and how it can benefit your plants.

What is a Fungicide?

Person applying fungicide on plants

A fungicide is a pesticide used to prevent, destroy, or control fungal infections on plants by killing fungi or inhibiting their growth and reproduction.

Fungi do not have chlorophyll and cannot make their food, so they depend on plants for food.

As they feed off the plant, they weaken it and make it more susceptible to disease and pests. Some fungi also produce toxins that can kill plants.

Fungicides control various plant diseases, such as mildews, rusts, blights, and leaf spots. They also prevent the spread of disease from one plant to another.


Related Post: The Difference Between Fungi and Bacterial Infections in Your Plants


How To Make a Bordeaux Mixture

Woman applying fungicide from a bottle onto her tree

The effectiveness of the Bordeaux mixture depends on following the right procedure and using the right proportions of ingredients.

The ratio of copper sulfate to calcium hydroxide to water is 10:10:100. You will need 10 pounds of copper sulfate and 10 pounds of calcium hydroxide for every 100 gallons of water.


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If you don't have a large enough container to mix all the ingredients at once, mix them in smaller batches. Just be sure to use the same ratio of ingredients.

Copper sulfate and calcium hydroxide are poisonous, so take precautions when handling them.

Wear gloves and a dust mask to avoid contact with skin and breathing in the powders.

1. Begin by Dissolving the Calcium Hydroxide

Calcium hydroxide

Soak the calcium hydroxide in a small amount before using it. This will make it easier to dissolve in the Bordeaux mixture.

Fill a bucket with 1 gallon (3.5l) of water and add 1 pound (453g) of calcium hydroxide. Stir until the powder is completely dissolved.

2. Dissolve Copper Sulfate in Water

Package of blue copper sulfate crystals

Add 1 pound (453g) of copper sulfate to a gallon of water and stir until it is completely dissolved. Let it sit for about 2 hours to give the copper sulfate time to dissolve fully.

3. Combine the Two Mixtures

Hand holding a blue bucket

Put 2l of water in a clean, plastic or metal container. Add the calcium hydroxide mixture and the copper sulfate mixture. Stir until everything is evenly mixed.

4. Apply the Bordeaux Mixture to Your Plants

Fungicide applied to plant leaves

The Bordeaux mixture is now ready to use. Use a garden sprayer to apply the mixture to your plants, and coat all the leaves thoroughly.

This homemade Bordeaux Mixture should be used the same day you prepare it for the best results.

Protect Your Vegetables From Disease With Bordeaux Mixture

Tomato plants in the garden

Making your own Bordeaux mixture is a safe and effective way to control fungal diseases on vegetables.

Apply the mixture before the disease appears for the best results. Copper sulfate crystals are a key ingredient in the Bordeaux mixture, which has been used for years to control fungal diseases.

We sell copper sulfate crystals of the highest quality and purity!

We take pride in providing our customers with the best products and services possible to support a healthy and beautiful garden.

Buy our copper sulfate crystals today to make your own Bordeaux mixture!



  • The formula ratio you recommended of the Bordeaux mixture is 10 lb : 10 lb : 100 Gallon respectively for Copper sulfate, Calcium hydroxide and Water, namely 1 lb : 1 lb : 10 Gallon or 454 g : 454 g : 38 Litter. However, in your example of making small scale of this mixture, you used 454 g for each of Copper sulfate and Calcium hydroxide, but the total amount of the water is only 9 litters (3.5 L + 3.5 L + 2 L) instead of 38 Litter. Please explain it or make a correction.

    Posted by Tommy | October 13, 2022
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