Powdery Mildew: Prevention and Control

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powdery mildew

Do you know that Powdery Mildew can affect your plants and is the most common fungal infection in plants?

Powdery Mildew is a fungi of the phylum Ascomycota of Kingdon Fungi.

Moreover, this disease is common, widespread, and easily recognizable. It is important to note that infection by fungi is due to high humidity not by free water alone.

Individual species of powdery mildew fungi often have a very narrow host range.

Unlike other fungal pathogens, powdery mildew tends to grow superficially or epiphytically on the surface of your plants.

During the growing season, plants produce hyphae on both upper and lower surfaces.

Though some species are restricted to one leaf surface only.

It is important to note that infection can also occur in other parts of the plant like stems, flowers, or fruit.

Keep on reading to learn more about powdery mildew in detail.

Powdery Mildew

Powdery mildew is a common fungus that tends to affect a wide range of plants and you can easily identify it.

It appears as light grey or white powdery spots on the surface of your plants. Most often it appears on the infected leaves.

However, you can also see them underneath the leaves, or on stems, flowers, fruit, or vegetables.

The spots tend to spread and will eventually cover most of the leaves, with new plant growth being most susceptible.

Moreover, powdery mildew tends to thrive in warm, dry climates.

But is also common in fairly high humidity, like the warm days and cool nights in late spring to early summer.

on plants

Furthermore, not enough sunlight and poor air circulation can also contribute to such conditions that encourage the growth of powdery mildew.

Although this disease is rarely fatal, if you do not treat your plants, it can eventually cause serious harm to your plants by robbing them of water and nutrients.

Mst infection causes minor damage like the leaves turning yellow or becoming withered or distorted.

However, your plants can also become weak, bloom less, and grow slower.

In a garden setting, it commonly affects cucurbits, i.e. squash, pumpkins, cucumbers, melons, nightshades, i.e. tomatoes, eggplants, peppers, roses, and legumes, i.e. beans, and peas.

Spread of Powdery Mildew

The spores of powdery mildew often drift into your garden with the wind.

However, if you have had powdery mildew occur in the past, new outbreaks can also come from dormant spores in old vegetative material or weeds nearby.

Moreover, unlike many fungal diseases, like black spot, this one thrives in warm, i.e. 60 to 80 degrees F, or 15 to 27 degrees C in dry climates.

Though it does require fairly high relative humidity, i.e. around your plant to spread as well.

However, in cooler, rainy areas, it does not spread as well.

And it is also slowed by temperatures higher than 90°F (32°C).

It also tends to affect plants that you place in shady areas more than those in direct sunlight.

Identifying Powdery Mildew

In order to identify plants with powdery mildew, read the following:

If your plant is affected with powdery mildew, it will look as if they have been dusted with flour.

This fungal disease often starts off as circular, powdery white spots, which can also appear on leaves, stems, and in some cases, fruits as well.

Powdery mildew often covers the upper part of the leaves. However, it can also grow on the undersides of the plants as well.


Moreover, young foliage is more susceptible to damage due to this disease.

Leaves tend to turn yellow and dry out due to this condition.

The fungus might cause some plants to twist, break, or become disfigured.

Furthermore, the white spots of powdery mildew will spread to cover most of the leaves or affected areas well.

Furthermore, the leaves, buds, and growing tips can become disfigured as well.

These symptoms often appear late in the growing season.

Susceptible Plants

It is important to note that there are not many plants that are completely immune to some form of powdery mildew.

This includes vegetables, roses, trees, and shrubs.

However, there are some plants that are more susceptible to powdery mildew than others.

These are:

  • begonias
  • lettuce
  • cucumbers
  • potatoes
  • parsley
  • pumpkin
  • grapes
  • peppers
  • tomatoes

Moreover, plants like sunflowers, chrysanthemums, dahlias, roses, zinnias, melons, zucchini, and squash are also most susceptible to this disease.

If you have recurring problems with powdery mildew, then make sure to look for varieties that are disease resistant.

You can find this information on the plant tags.

Treatment Options

Though most products on the market are targeted more toward the prevention of powdery mildew. there are a number of home remedies to treat an existing infection.

Spray mixtures will only kill what they come in contact with, for instance. So you will have to make sure to coat all the affected areas thoroughly.

Moreover, it can take multiple applications for complete treatment.

Apply once a week for three to four weeks, and then wait to see the results. You can reapply as needed.

Treatment options are:

Baking Soda Solution: Mix 1 tablespoon baking soda and 1/2 teaspoon liquid soap like castile soap not detergent in 1 gallon of after.

Spray liberally, getting top and bottom leaf surfaces and any affected areas.

powdery mildew 1

This method tends to work better as a preventive measure, though it does have some effect on existing powdery mildew as well.

Potassium Bicarbonate: Mix 1 tablespoon of potassium carbonate and 1/2 teaspoon liquid soap not detergent in 1 gallon of water.

Make sure to sprat liberally to all the affected areas.

Moreover, this mixture may work better than baking soda as a treatment for existing infections as well.

Milk: Mix 1 part milk to 2 to 3 parts water and spray on your plant liberally.

While the science behind this solution is not fully understood, it seems to work well, especially on plants like zucchini, melons, and cucumbers.

Furthermore, many believe that naturally-occurring compounds in the milk not only combat the disease but also boost the immune system of the plant.

Other Options

Some other options are:

Neem Oil: Although neem oil for the powdery mildew has mixed reviews on its effectiveness to treat powdery mildew.

However, you can add it to the above mixtures for an extra boost.

Trim or Prune: Remove the affected leaves, stems, buds, fruit, or vegetables from the plant and discard them.

Additionally, some perennials can be cut down to the ground and new growth will emerge.

However, make sure to avoid composting any damaged or diseased foliage as the spores can spread and persist in the composted material.

Make sure to disinfect pruners and all tools after using on the infected plants.

Fungicides for Powdery Mildew

There are a number of fungicides, especially for rose bushes, that are highly effective with low toxicity, no residue, and long duration.

You can apply sulfur or copper-based fungicides to prevent infection of susceptible plants.

For best results, apply early or at the first sign of the disease.

Spray all plants thoroughly and repeat at 7 to 10-day intervals up to the day of harvest.

You can also use a fungicide that contains a patented formula of potassium bicarbonate, which is commonly found in food products.


It helps to kill many plant diseases on contact and provides up to 2 weeks of residual protection.

At the first sign of disease, mix 1 to 2 tbsp per gallon of water and apply it to all exposed surfaces of the plants.

Moreover, you can also use broad-spectrum bio-fungicide that uses a strain of Bacillus subtilis that is for organic gardening.

It is safe to use and you can treat and pick crops on the same day as well.

Furthermore, fungicides with 100% pure food-grade ingredients work fast to kill existing plant diseases and help to prevent new fungal problems from starting.

Treating Powdery Mildew on Roses

In order to treat powdery mildew on roses follow the step below:

Remove and discard any affected leaves, as well, as any of those that have dropped to the ground.

Treat the rest of the plant preventatively.

However, if you see powdery mildew on buds, clip, and discard them as well.

powdery mildew on rose

Thoroughly clean and disinfect any cutting tools that you use in this process.

Moreover, make sure to apply one of the treatments above like a fungicide, baking soda, potassium bicarbonate, or milk mixture once a well for 3 to 4 weeks and wait to see the results.

Prevent any further outbreaks with regular applications every couple of weeks or follow directions on product labels.

With time, results tend to get better in your treating the infection at the first signs and getting rid of it quickly.

Prevention Tips

The following are some of the things you can do to control powdery mildew before it occurs:

Thin out any existing susceptible plants to improve the airflow within the plant.

Make sure to maintain adequate spacing between the plants and keep them far enough from the walls and fences.

This helps to make sure there is good air circulation and helps to reduce relative humidity.

Locate your plants in proper sunlight according to their specific needs.

Maintain healthy plants by removing any dead or diseased foliage.

Disinfect the pruners or shears after using them on infected plants.

As new growths tend to be more susceptible, therefore, be careful to avoid overfertilizing.

This is because it can cause a rush of new foliage.

Treat your plants regularly with an organic fungicide that contains sulfur as an active ingredient.

You can use it as a preventive measure as well as treatment for existing powdered mildew.

When shopping for plants, make sure to choose plants that have increased resistance to powdery mildew.

Wrapping it Up

Powdery mildew is a fungal disease that tends to occur in a number of plants and is easily identifiable. With treatments above, like using an organic fungicide, baking soda, potassium bicarbonate, etc, you can treat and even prevent future infections.

however, once your plants are heavily infected, it is difficult to get rid of the disease. Thus, focus on preventing it from spreading to other plants. Remove all infected foliage, stems, and fruit and destroy them.

You can do so by either throwing them in the trash or by burning them. Make sure to avoid composting them as the disease can still spread by the wind and persist in the composted materials.

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