What Is Copper Fungicide and How Do You Use It?

In warm, wet weather, fungal disease tends to plague garden plants. 

Rather than using dangerous chemical fungicides, many gardeners choose to use copper fungicides. 

copper fungicide label

It may surprise you to know even though it is a metal; copper can dissolve in a way allowing it to penetrate deeply into plant tissues to provide optimal prevention and control of a wide variety of fungal diseases, such as:

When used correctly and at the right time, copper fungicide provides good protection against these particular diseases, but there are some considerations to keep in mind.

#1 – Limited effectiveness: When using a Copper fungicide, timing is an important consideration. 

For example, this type of fungicide is not especially effective when used against the late blight of tomatoes and potatoes.

#2 – Toxicity: You must be very careful to follow packaging directions precisely because copper is toxic. 

If used incorrectly, it can cause a great deal of damage to plant tissues.

#3 – Varying product results: There are many different types of copper products available, and these vary a great deal in terms of rate of application and the amount of copper and other active ingredients included. 

For this reason, you must review packaging directions every time you use a copper fungicide, especially if you are changing from one product to another.

#4 – Soil contamination: You must use copper fungicide very sparingly because it doesn’t break down in the soil. 

Over time, it builds up and becomes a hazardous contaminant.

What Damage or Condition Does Copper Fungicide Control?

It’s important to understand copper fungicide is a deterrent, not a cure. 

It’s best to set a regular schedule of use to prevent and control the development of fungal infections. 

It will not cure existing infestations.

If you catch a fungal disease (based on early symptoms or conditions) very early on, before you see the fungus, it may be helpful. 

Otherwise, use it as a safeguard early on when weather conditions would predispose your plants to develop the fungal disease.

You may also want to use it as a preventative on healthy plants if you see fungus on one plant or if you have accidentally brought in a plant with a fungal infection. 

In this case, you would want to remove the infected plant and treat the rest with copper fungicide.

How and When To Use Copper Fungicide?

Generally speaking, you would mix 1 to 3 teaspoons full of copper fungicide with a gallon of water to be used as a spray application. 

As noted, these are just general directions. 

Remember always to read the specific directions for the product you are using every time.

These products tend to degrade within a few days of application, so they must be reapplied for the best results. 

Most copper fungicide products are applied on a weekly basis. Apply some every ten days.

Even though copper fungicide is not known to be harmful to bees, we must be careful to protect the dwindling bee population in every way possible. 

For this reason, you should never apply copper fungicides to plants where bees are actively gathering pollen.

Apply the products late in the day after bees, and other pollinators have stopped foraging. 

This will give the product time to dry out before they begin hunting for pollen again when the sun comes up.

When in Doubt Seek Help

Many gardeners swear by copper fungicides as a way of keeping fungal infections under control and protecting Hemlock type plants such as eggplant, potatoes, and tomatoes, as well as squash and cucumbers.

The use of copper fungicides is a little bit confusing, but as long as you’re very careful about following packaging instructions, you should encounter few problems. 

If you have questions about the use of copper fungicide in your specific situation, get in touch with your County Cooperative Extension Office to find out exactly what is recommended in your area.

Resource: Copper Fungicide Technical Fact Sheet