6 Organic Ways to Control Powdery Mildew

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6 Organic Ways to Control Powdery Mildew

6 Organic Ways to Control Powdery Mildew

Powdery mildew is a fungal disease that affects a wide variety of plants. It's most common on leaves, but it can also affect stems, buds and even roots. The problem with powdery mildew is that it feeds on the chlorophyll in the plant and causes it to turn white or yellow. This unsightly condition can dramatically lower a plant's market value and even cause the plant to die. There are several ways you can help control powdery mildew including using biological controls, physical controls and fungicides.In this blog, we'll discuss the causes of powdery mildew as well as the organic methods for controlling it. 

Causes of Powdery Mildew

The primary cause of powdery mildew is excessive moisture. Moisture encourages the growth of the fungus and keeps it alive. If your plants are getting too much water, they will be more susceptible to powdery mildew. It's important to remember that not all plants are affected by powdery mildew. Some plants, such as tomatoes, peppers, eggplants and potatoes are especially resistant. On the other hand, many ornamental plants like begonias, impatiens, petunias, marigolds and zinnias are very susceptible to powdery mildew. Moisture can also cause problems with plant diseases. For example, when plants get too much water, they develop "damping off". Damping-off is a condition where the roots of the plant simply die because they can't get enough oxygen. When this happens, the plant cannot absorb enough minerals and nutrients from the soil and it dies.
In addition to excessive moisture, excessive heat also contributes to the spread of powdery mildew. High temperatures cause the spores of powdery mildew to become active and produce more offspring. This increases the likelihood that your plants will get powdery mildew. In fact, many gardeners believe that temperatures above 70°F help to make plants more susceptible to powdery mildew. If you live in an area where the temperature regularly exceeds 70°F, you should try to keep the temperature in your greenhouse or outdoor grow room as low as possible. You can do this by using a good quality heating mat under your plants. Make sure the mat has a zippered opening so you can add or remove it as needed. Also, if possible, try to position your grow room (or greenhouse) as far away from direct sunlight as possible. This will help keep the interior of your growing space at a lower temperature.

How Do Mildew Harm Plants?

Although powdery mildew does not usually kill a plant, it can cause the plant to become malnourished. This makes the plant vulnerable to other problems such as root rot and wilting. When plants are infected with powdery mildew, they produce more spores than usual. These spores are easily spread to nearby healthy plants by wind and water. As these spores infect more and more plants, the amount of mildew on the infected plant increases. Soon, the entire plant community is infested. This eventually causes the leaves of the infected plants to turn yellow and fall off.
In areas where powdery mildew is a problem, you should try to maintain a "mildew-free" environment in your greenhouse or outdoor grow room. If possible, avoid overhead irrigation. Use drip or trickle irrigation instead. Make sure all plant surfaces are well-drained. Keep the humidity at or below 70%. And, if possible, grow your plants in a "mildew-free" area. By doing this, you will help prevent the spread of powdery mildew.

How to Get Rid of Powdery Mildew with Organic Remedies

If you would like to use natural remedies to control powdery mildew, here are some things you can do:

1. Cut and remove infected leaves:

Remove and destroy any and all infected leaves. This will not only remove the mildew but will also stimulate the plant to produce new, healthy leaves.

2. Spray the plant with baking soda:

Mix one-half cup of baking soda with one gallon of water. Using a spray bottle, spray the mixture on the plant. Let the mixture sit on the plant for a few minutes. Then, brush off the plant with a soft cloth. Repeat the process once a week until the powdery mildew is gone. In contrast to most commercial fungicides, this method is safe for plants, people and the environment.

3. Use potassium bicarbonate:

Like baking soda, potassium bicarbonate is an alkaline compound that kills and controls many fungal diseases. It works much like baking soda. Apply it as a dusting powder to the plant by brushing it on the leaves and stems. Do this weekly until the disease is under control.

4. Neem oil spray:

Mix one-half cup of neem oil with one quart of water. Use this mixture as a spray to control powdery mildew. Spray the mixture on the plant at least twice a week. Allow the mixture to dry on the plant before watering again. This will help the oil become "truly" dry and kill the powdery mildew. Too much application can cause your plant to become leggy (have weak stems). Reduce application if this occurs.

5. Use sulfur:

Mix one part sulfur with three parts salt and apply the mixture to the infected area of the plant. Wait a few minutes and then water the plant thoroughly. This will kill the mildew and remove any harmful residue left over from the sulfur. In fact, sulfur is one of the best all-purpose fungicides you can use. It is safe for both people and pets and it works on most plants. However, it must be used in combination with other remedies since it doesn't stay on the plant long enough by itself to be effective.

6. Use copper:

Apply copper in the form of copper sulfate to the soil around the infected area. This will prevent the spores from spreading to other areas of the plant. Wait a few days and then water the plant thoroughly. This will kill the mildew and remove any harmful residue left over from the copper. It's important to use copper when combating powdery mildew since it will kill many other beneficial fungi and bacteria in the soil as well.


Powdery mildew is one of those fun, little annoyances that plague gardeners year-round. Controlling powdery mildew can be frustrating. In this blog, we have discussed some simple and easy ways to help prevent powdery mildew and they won’t cause any harm to your plants. You should test each of these methods on a few plants you are particularly concerned with to make sure they work before trying them on a large scale. What other organic ways do you know of to control powdery mildew? Please share your thoughts in the comments section below.