How To Treat Powdery Mildew On Houseplants

Despite your best attempts, powdery mildew may still affect your plants. There are numerous ecologically responsible ways to treat the condition, including:

soda bread. Although baking soda by itself is typically ineffective for treating powdery mildew, when coupled with water and liquid soap, it can be a potent tool. In most cases, using it as a preventative strategy as opposed to a therapy is more advantageous. Spray the plants thoroughly with a solution of one gallon of water, one tablespoon baking soda, and one-half teaspoon liquid, non-detergent soap.

Mouthwash. Powdery mildew spores can be killed with the same mouthwash that you use every day to destroy the bacteria in your mouth. The powdery mildew spores cannot endure it because its purpose is to kill bacteria. It has been shown that a decent ratio is three parts water to one part mouthwash, but exercise caution because mouthwash is powerful and can harm new growth.

Milk. A promising method for preventing powdery mildew is emerging: milk. Although the science isn’t fully understood, it’s possible that the molecules in milk can function as an antiseptic and fungicide as well as possibly boosting the plant’s overall immunity. It frequently works effectively as a defense against powdery mildew on cucumbers, other squash, and zucchini. One part milk to two or three parts water is an efficient mixing ratio.

Treatments with organic fungicides. There are several commercial treatment alternatives that are equally as environmentally responsible and authorized for organic gardening if you don’t want to try to solve the problem yourself. By choosing this course, you will also be able to precisely identify the pests that the treatment will kill and the plant varieties that it will benefit.

Water. Watering your plants overhead and thoroughly wetting them can assist, as powdery mildew growth is frequently caused by dry circumstances combined with high humidity. However, it’s crucial to employ this technique only sometimes because overwatering might harm your plants in other ways.

What rapidly eradicates powdery mildew?

Keeping your garden’s air moving enough will help prevent powdery mildew.

According to the volume of inquiries I receive each summer on the powdery mildew plant fungus, I’ve discovered three things over the years: it’s common, you don’t like it, and you want to know how to get rid of it. So, here’s what you need to know to stop it from happening in the first place, manage it, and even get rid of it.

One of the most pervasive and readily recognisable plant fungal diseases is powdery mildew. Almost no plant is immune, from vegetable gardens to rose gardens, ornamental trees, and shrubs.

Don’t be alarmed if you discover that any of your trees or plants have powdery mildew. Because this fungus is host-specific, it doesn’t necessarily mean that other types of plants in your landscape are in danger just because you detect it on one variety of plant. Despite the fact that powdery mildew has numerous species, all of its symptoms are rather uniform.

Most certainly, you’ve seen it before. Powdery white or gray patches develop, frequently covering the majority, if not the entire leaf surface. Additionally, fruit, flowers, and plant stems can all contain it. Fortunately, the harm caused by powdery mildew is typically worse than its symptoms. It rarely kills the plant.

The plant may prematurely defoliate as a result of advanced stages, which can cause the leaf to yellow, curl, or turn brown. The fungus can cause early bud drop or reduced bloom quality on trees and flowering plants.

Dry foliage, high humidity, low light, and moderate temperatures are all factors that encourage mildew growth. Proactive measures to steer clear of or reduce this risk include:

Look for kinds that are disease-resistant. For information on specific cultivars and varieties, get in touch with your county extension service.

Plants should be placed where they will receive at least six hours of light per day. Reduce the amount of shade and prune any light-blocking trees and shrubs.

Refrain from overfertilizing. Fresh growth is more prone. Apply a slow-release fertilizer in its place for more carefully regulated growth.

Early detection is the greatest approach to contain and maybe get rid of the issue if you need to respond to a powdery mildew condition that already exists. There are numerous commercial goods that are successful at keeping the spread under control. However, solving an existing issue is not always a guarantee.

Most conventional products are designed for prevention and control, not for the eradication of an infection that has already taken hold. For this reason, it’s crucial to begin a control program before powdery mildew appears, or at the very least, at the first indication of detection.

For the treatment of mildew, numerous over-the-counter, retail fungicide treatments are available. “Chlorothalonil” is one of the most often utilized active components for control. Despite being effective, it leaves a clear white milky film on the leaf surface.

Less popular choices include:

The most well-known of the natural, homemade remedies for powdery mildew is probably baking soda (sodium bicarbonate). Studies show that using baking soda alone is not particularly effective, but when combined with horticultural grade or dormant oil and liquid soap, efficacy is quite good if used early on or before an outbreak develops.

Utilize this formula to create your own remedy.

To a gallon of water, add one tablespoon of baking soda, one teaspoon of dormant oil, and one teaspoon of liquid soap (not detergent) that is insecticidal. Every one to two weeks, spray your plants.

bicarbonate of potassium This has the distinct advantage of actually getting rid of powdery mildew once it’s there, much like baking soda does. A contact fungicide called potassium bicarbonate immediately kills the powdery mildew spores. It is also permitted for use in organic farming.

If mouthwash is effective at killing oral bacteria, powdery mildew fungus spores can’t hope to compete. And that is the basic idea. Generic mouthwash with an ethanol basis has a high degree of controllability. Jeff Gillman, a Ph.D. and Associate Professor at the University of Minnesota’s Department of Horticulture, found that tests using one part mouthwash to three parts water performed well. Just be cautious while combining and applying mouthwash because you don’t want to harm fresh foliage.

VinegarVinegar contains acetic acid, which works similarly to mouthwash in controlling powdery mildew. A gallon of water mixed with two to three teaspoons of regular apple cider vinegar (5 percent acetic acid) works well. Although larger amounts (over 5%) of vinegar are more beneficial, too much of it might burn plants.

Lime with Sulfur/Sulfur

Direct contact with sulfur stops the growth of disease spores. The solution will penetrate leaves for even greater efficiency when combined with hydrated lime. The Bordeaux mix, a widely used variant of this mixture, consists of copper sulphate and hydrated lime. All of these remedies have the potential to burn plant tissue, harm soil microbes, and kill beneficial insects. It is also regarded as having a mild toxicity to humans and mammals. If at all, use with caution and sparingly.


Milk is the newest participant in the conflict with powdery mildew. It is thought that naturally existing components in milk are at work to fight the disease while also bolstering the plant’s immune system. The exact reason it works so well is yet unknown. One trial that used a weekly dose of one part milk to two parts water produced positive outcomes.


Ironically, dry weather and high humidity are ideal for the growth of powdery mildew. Straight water, however, works against it because it washes the spores away before they have a chance to implant. However, I do not advocate the use of water as a control measure because moist foliage is a friend to numerous other plant diseases. If you decide to use this strategy, do it early in the day so that the foliage has time to quickly dry off.

Hemp oil

This is a convenient organic alternative for disease and insect control. Neem oil is extracted from the neem tree, native to India. This natural pesticide has a broad spectrum, is excellent at controlling disease, and is less harmful to mammals and helpful insects. The best method for preventing powdery mildew has mixed results. Results are often at best average.

Even with a wide range of management options, prevention remains the best treatment for diseases like powdery mildew as well as other conditions.

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How is powdery mildew treated?

Although powdery mildew can be found in almost every growth zone, it prefers environments with lengthy stretches of warm, dry weather. Similar to how PM can go very out of control in our garden here on the temperate Central Coast of California if left unchecked! However, powdery mildew enjoys a little dampness as well, just like any other fungus would. The fungi are encouraged to grow by the moisture in humid air (or nighttime dew), and the spores are disseminated by the warm, dry air throughout the day.

Although they can survive or overwinter in soil, compost, mulch, or other plant waste, powdery mildew spores primarily thrive on plants. Wind, insects, water splashing, or direct contact with diseased plants are some of the ways that the spores are transferred from plant to plant (or are first brought into your garden). Powdery mildew is also more likely to grow in crowded areas, places with poor airflow, and in shade.

Light grey or white, dusty-looking patches or blotches are the hallmarks of powdery mildew. They are typically rounded, fluffy, and occasionally somewhat elevated. The telltale dots will initially be visible on the tips of plant leaves. If you look closely (or as the illness worsens), you could notice mildew on stems, the undersides of leaves, on blooms, and occasionally even on the actual fruit or vegetable. The plant looks as though it has been sprinkled with flour or powdered sugar when it has a severe case of powdery mildew. Eventually, the diseased leaves could dry out and turn yellow.

Once you are familiar with powdery mildew, identifying it is not too difficult. However, it could be mistaken for other fungi-related illnesses, like downy mildew (which causes darker spots on leaves instead). Even more, sometimes natural patterns on plant leaves might resemble mildew as well! Take a look at the illustration of our zucchini plant below, for instance. Some melons, squash, and zucchini plants naturally have white spots or variegation on their leaves, depending on the variety.

The main distinction is that a naturally occurring leaf pattern will be flat (not fuzzy or dusty) and appear more uniform, most likely “mirrored across both sides of leaf veins. Mildew spots, on the other hand, typically appear on the top and bottom sides of leaves and are much more sporadic in their distribution. In contrast to the natural leaf pattern, PM can be removed with a damp cloth or paper towel (or at least made to momentarily appear to do so).

The good news is that plants seldom die from powdery mildew. But that doesn’t imply you should ignore it just because it won’t kill you. A few little spots won’t initially do any damage to the host plant, but they can transfer spores to other plants or remain in the soil of your garden. The fungus feeds on and steals nutrients from the plant as the condition worsens, leaving it stunted or less productive.

Photosynthesis can be hampered when powdery mildew covers a substantial section of leaves. For the plant, this is essentially a slow famine. Since the plant will be producing fewer sugars as a result of a change in photosynthesis, crop flavor may also be affected. Last but not least, infections with powdery mildew stress plants, and stressed plants are more vulnerable to other illnesses or pest damage.

In general, people are not harmed by powdery mildew. It is therefore neither harmful nor poisonous. However, some people are allergic to mildews and mold and are therefore advised to proceed with caution. We have undoubtedly consumed our fair share of crops with a few mildew patches as mildew is pretty prevalent in our garden (I hate the idea of wasting food). We simply thoroughly wash the produce before eating it, but we do not eat any pieces that are seriously diseased.