Powdery Mildew Treatment | Symptoms and Solutions

It feels amazing to grow herbs, veggies, and other plants of our own. But it is disappointing to deal with the white patches on our plant leaves. So we keep wondering about the most effective powdery mildew treatment.

Powdery mildew is common type of fungus disease during the warm rainy season. It can infect almost 12,000 species of plants worldwide. It suffices to say that only the resistance species of plants are safe from this disease. It can cause a huge loss of the plants in both gardens and farming fields.

So it is imperative to identify and treat and control this disease as early as possible. Let’s know about the symptoms, treatment and control of powdery mildew.



The name “powdery mildew” is self-explanatory. It is a common type of fungus issue. It works in a series of Erysiphales. So there are more than hundreds of species of fungi in this series. It causes a white or gray form of powdery film on various parts of the plants.

The powdery film consists of mycelia and spores in general. But the taxonomy of Erysiphales series is different now. In 2000s, scientists have discovered a new DNA pattern of this fungus disease. So it can be anything among the hundreds of species of fungi.

The reproduction process of powdery mildew is simple as well. It works both asexually and sexually. The asexual stage spread this disease using spores. The Chasmothecia generates fruiting bodies in sexual stage. Scientists have also found Podosphaera and Golovinomyces that attack roses and cucurbits respectively.



Powdery Mildew has very specific set of symptoms. There could be a few types of powdery mildew based on hundreds of species of fungi. But the symptoms are almost same.

How it looks like:

  • It causes a white or gray form of powdery film on various parts of the plants.
  • You will notice this powdery film on the plant foliage, fruit and steams.
  • Sometimes it also forms a grayish talcum-like powdery film as well.
  • It may look like dusting of flour to the ordinary gardeners or framers.
  • It takes the size of a pinhead gradually.

How it affects:

  • It impairs the photosynthesis process. So it causes the leaves to fall prematurely.
  • It sucks up the causes important nutrients. Thus, the leaves look wither and yellow. It may also turn the leaves black eventually.

Symptoms may vary:

  • The loss of leaves causes sunscald to fruits on cucurbits.
  • We notice brown scabby spots on some sort of succulents.
  • You may also find corky brown spots on the kalanchoe.
  • There are pale yellow leaf spots on tomato plants.

It attacks the lower foliage of your plant first. It starts to spread the whole plant over time. It can also overwinter in warm rainy climates as well. Simply, warm climate, dense plants and higher humidity cause this disease to foster.


Researchers have found almost 12,000 species of plants prone to this disease.  Yet there are some hybrid species of plants and powdery mildew resistant plants. You will find conifers and other gymnosperms in the hybrid and resistant category.

So it can affect almost any kind of plants.

Ornamental Plants: Powdery mildew attacks all the common types of ornamental plants. It can affect:




Bee balm













Fruits and Vegetables: These fruit and vegetables are susceptible to powdery mildew:




















Greenhouse crops: Even the greenhouse crops can face this disease:






Gerbera daisy



African violet


Herbs: These types of herbaceous perennials are also susceptible to it:









Phlox and rosemary


Mildew on grape: Nowadays powdery mildew affects grape as well. So you must be careful about you grape plants and take proper safety precautions. Stay more attentive in warm and rainy weather condition.





Dry and warm condition with moderate temperature causes powdery mildew. Low lighting, high humidity and dry foliage are also prone to this disease. Free water condition is not essential here.

So it affects the plants highly during the late spring and fall at high humidity.


You may like:

Fungus Gnats | How To Get Rid of Gnats On Plants



Yes, it can spread to other plants. High wind easy spread the spores of these fungal pathogens. So it can also affects the other plants over time. But If you take popper steps to get rid of it immediately, you can stop it from spreading to other plants.


Free water is not necessary for powdery mildew to infect the plants. Free water may turn out to be destructive for it by killing the spores of these fungal pathogens. So it attacks the plants easily in dry and warm condition without free water.

Water Conditions:

  • It requires considerable humidity to germinate the spores.
  • The higher the humidity rate, the higher the germination rate.
  • It infects mostly at night in higher humidity.
  • 70-80°F is considerably moderate temperate for powdery mildew. So it affects highly at this temperature.
  • High temperature difference between day and night helps it to foster.
  • Late spring and fall is the perfect time for it to affect in many region.
  • High wind also increases the spread of spores.

Other Relative Conditions:

  • Crowded plants have poor airflow and damp condition. So they are more susceptible to this disease.
  • Stressed and physically weak plants are susceptible too.



You can remove and dispose of all the infected plants to get rid of powdery mildew. But we don’t like to lose our plants most of the time. It is not practical for all the plant growers.  So we prefer to use various kinds of treating procedures of powdery mildew.

There are two ways to control powdery mildew:

  1. Cultural & Physical Controls
  2. Biological & Chemical Controls

To control mildew, you must follow the procedures:

  • You can use preventative fungicides on the infected plants.
  • You must use them at the outset of the powdery mildew infection.
  • Effective organic fungicides are also available.
  • You can also use bicarbonate solutions instead of the chemical fungicides. These are baking soda or milk fungicides.
  • If it spreads heavily, you must stop it by removing the infected plants. Wind can spread the spores of these fungal pathogens and infect the other healthy plants. So remove and dispose of all the infected leaves or foliage, fruits and the steams.


Now will we discuss about the best powdery mildew treatment ways. Some of them are organic, and some are not. We have included both chemical fungicides and bicarbonate solutions.


Rose powdery mildew treatment:

It is very easy to treat rose powdery mildew. You should go for both cultural and biological or chemical control. We recommend you to use organic fungicides to treat powdery mildew on roses. The most effective fungicides are baking soda, potassium bicarbonate or milk fungicides.

  • Remove and dispose of all the infected plants.
  • Remove and destroy all the partially infected leaves.
  • Be very careful about the already dropped leaves as well.
  • You should also remove the infected buds, fruit and steams.
  • Clean and disinfect all the plant clippers used for cutting the plants portions.
  • Use fungicides for once a week for 20-30 days.
  • You should also apply the fungicides regularly in every 2-3 weeks. It will prevent further infection.

Powdery mildew treatment organic:

We all know about the chemical preventative fungicides. But there are some organic powdery mildew treatments as well. It is more preferable than the severe chemical fungicides.

There are a few types of organic fungicides. You can try any of them. But the best way is using the potassium bicarbonate solution:

You will need:

  • Potassium bicarbonate (3 tablespoons)
  • Vegetable oil (3 tablespoons)
  • Dish soap (1-2 tablespoons)
  • Water ( 1 gallon)

Mix these elements properly to get the bicarbonate solution. Spray it once a week. It will raise the plant pH level to 8.3 and stop the mildew growth.

Another popular way is the use of dilute solutions of hydrogen peroxide:

You will need:

  • Hydrogen peroxide
  • Water

Mix hydrogen peroxide and water in 1:9 ratios in a pot. Then use it thoroughly on your plants. You should use it once a week until you get rid of powdery mildew completely.

Other organic powdery mildew treatments include:

  • Sulfur
  • Vinegar
  • Mik
  • Baking Soda
  • Copper
  • Neem oil
  • Lime-sulfur
  • Garlic fungicide.

Safety precautions for organic powdery mildew treatment:

  • Keep the garden moisture level accurate
  • Don’t raise the humidity level of the garden
  • Follow the annual pruning schedule

Squash powdery mildew treatment:

Organic fungicides are effective for squash powdery mildew treatment. But the milk fungicide is the best.  It not only prevents the spread of mildew spores, but also boosts the immunity of the plants. Other organic options you can apply:

  • Stylet or sulfur oil
  • Copper fungicides
  • Neem oil is also very effective.

You can also apply horticultural oil for severe powdery mildew attack.

Follow the procedure:

  • Get rid of the infected plant portions.
  • Apply any of these fungicides.
  • Apply it in 7-14 days interval.
  • You must apply horticultural oil once in every 10 days.

Cucumber powdery mildew treatment:

There are a few types of treatment procedures for cucumber powdery mildew. Not all are equally effective. The most common type of treatment is using chlorothalonil. You can also use DYI technique and use organic elements as well. All type of organic fungicides is equally effective. But we recommend to use baking soda or fungicide.

You will need:

  • Baking soda (1 tablespoon)
  • Dormant oil (1 teaspoon)
  • Liquid soap or insecticidal (1 teaspoon)
  • Water (1 gallon)

Follow the procedure:

  • Remove the affected plant portions.
  • Mix the elements and prepare the solution.
  • Apply it on the plants in every 10-14 days.
  • Keep applying for 2-3 months for the optimal result.
  • Water the infected plants for 2-3 days before applying the solution.

Note: Follow the same procedures for other organic fungicides.

Peony powdery mildew treatment:

It is usually very hard to treat powdery mildew on peonies. But you are never out of options. Traditional fungicides might help in treating peony powdery mildew. But sometimes in may not work efficiently. Then you will need horticultural oil or neem oil to get rid of it.

You will need:

  • Baking soda
  • Canola or horticultural oil
  • Liquid dish soap
  • Water (1 gallon)

Follow the procedure:

  • Get rid of the infected foliage, fruit and steam as usual.
  • Mix all the elements and prepare you solution.
  • Apply the solution thoroughly on the infected plants.
  • Maintain an interval period of 10-14 days.
  • Keep applying throughput the summer season.

Note: Sunny and hot days are not suitable for applying this solution. You must also test how a plant response before applying it on all plants.

Powdery mildew treatment baking soda:

Baking soda can be a very effective treating element for powdery mildew. But you have to mix it with water, and non-detergent liquid soap. It works as an organic preventative fungicide. Regular spraying can also prevent further infection.

You will need:

  • Baking soda (1 tablespoon)
  • Non-detergent liquid soap (1/2 teaspoon)
  • Water (1 gallon)

Follow the procedure:

  • Remove the infected leaves and other plant portions.
  • Clean and disinfect all the plant clippers used for cutting the plants portions.
  • Mix the elements and make your baking soda fungicide
  • Pour the mixture in a sprayer.
  • Apply it on the plants thoroughly. Be careful about spraying under the leaves, fruits and steams.
  • Depose of the unused solution.

Note: It may not be suitable for all the plants and burn the foliage sometimes. Water the plants for 2-3 days before you apply this solution.

Remove Infected Portions of Plants:

Wind can spread the spores of these fungal pathogens and infect the other healthy plants. So remove all the infected leaves or foliage, fruits and the steams. You can use plant clippers to removes the infected parts. But wash them properly using alcohol. Never compost the infected portions.



You must maintain interval periods in treating powdery mildew. There are interval periods for all kind of treatment procedures. You must also maintain an interval period for organic fungicides as well. Otherwise, you will end up affecting your plants instead.

  • Apply milk fungicides in every 10-14 days.
  • Apply neem oil, hydrogen peroxide, PM wash and potassium bicarbonate once a week.
  • Apply copper or sulfur fungicides in 7-10 day intervals.

Note: It is better if you maintain PHI or pre-harvest intervals for edible crops.


Let’s know about various types of contact fungicides.

Contact fungicide:

Contact fungicide is preventive or protective fungicide. It has barrier and smothering effect. It does not enter into the plant tissue. It protects only that part of the plant where you spray or apply them. You must apply it on the plant surface before it can penetrate the plant tissue.

The most common type of contact fungicide is potassium bicarbonate. You can find this fungicide in GreenCure as well. It is effective against downy mildew, powdery mildew and other type fungal issues.

Contact materials:

Simply, contact materials are all types of preventive or protectant fungicides. We know about protectant and systemic fungicide. We use contact materials or  mostly to control fungal problems.

Contact materials stay on the plant surface. It kills the hyphae and fungal spores upon contact. Thus, it prevents the fungal infection.

Multi-site contact:

Multisite contact fungicide belongs to low resistance risk group. It is also a kind of contact fungicides. But it differs in the combination and application. It is a combination of chlorothalonil and mancozeb.

You can mix it with any fungicide of single or high resistance risk group. It stays on the surface of the plants and act as a shield against powdery mildew. Thus, the mildew spores cannot infect the plants. It also attacks various proteins and enzymes to keep the pathogens guessing


What is the best treatment for powdery mildew?

Organic fungicides are best for powdery mildew treatment.  The best organic fungicide is potassium bicarbonate. It is far better than baking soda and kills the powdery mildew rapidly. So the unique advantages of potassium bicarbonate make it the best organic fungicides.  Organic fungicides are also preferable to chemical fungicides as well.

What is the best fungicide for powdery mildew? 

You will find various types of fungicide for powdery mildew in the market. But the ones with potassium bicarbonate is the best fungicide for powdery mildew. Other elements effective elements are copper, neem oil and sulfur. You can also make milk or baking soda fungicide yourself.

Can plants recover from powdery mildew?

Yes, plants can easily recover from powdery mildew if you take proper steps. Healthy plants can ward off this infection alone. They can also recover alone without any treatment. If you take steps to control powdery mildew timely, plants will recover from it.

How do you get rid of powdery mildew forever?

There is actually no way to get rid of the powdery mildew forever. Potassium bicarbonate fungicide is very effective. The GreenCure fungicide is also considerably effective. It contains potassium bicarbonate and sodium bicarbonate at a time.

What is the life cycle of powdery mildew? 

Powdery mildew has a combined life cycle of both asexual and sexual stage. The asexual stage produces conidia and spread this disease using spores. The Chasmothecia generates fruiting bodies in sexual stage.

Should I remove leaves with powdery mildew?    

Yes, you should remove the leaves with powdery mildew. Wind can spread the spores of these fungal pathogens and infect the other healthy plants. So remove all the infected leaves or foliage, fruits and the steams.

Does sunlight kill powdery mildew?

Yes, direct sunlight kills the powdery mildew spores. It cannot spread without moderate temperature.

How do I get rid of downy mildew ?

  • Remove all the infected plants right away.
  • Remove all the infected leaves.
  • Take measure to ensure high airflow.
  • Do not water the plants
  • Use preventative fungicides.

The best preventative fungicide for downy mildew is Bonide Copper fungicide.  You can also use Chlorothalonil and mancozeb fungicides.

What happens if you eat powdery mildew?

Powdery mildew is not harmful to humans. If you eat powdery mildew, it can cause allergic reactions at most.

Will dish soap kill powdery mildew?

Yes, it will kill powdery mildew if you use it properly. Use dish soap mixing with baking soda, vegetable oil, or water. You can also mix it with a 1:9 water and mik combination.

1 thought on “Powdery Mildew Treatment | Symptoms and Solutions”

Leave a Comment