The White Dust on Your Leaves, Explained
What this common fungus does to plants, and a natural way to stop it.
As humans, we put up with a lot of mildew. It tends to grow anywhere that there is moisture. Often, this menace goes ignored, where it lurks in between bathroom tiles and eventually becomes a gross part of the scenery.
If you don't want to scrub the mildew from your shower, that's your business, but why should your plants have to suffer? Mildew - specifically powdery mildew - is one of the most common diseases affecting plants and flowers. But what is it, and can it harm your beloved zinnias?
If nothing else, reading up on houseplant care can help you procrastinate on cleaning the bathroom for a while longer! Read on to learn more about powdery mildew on plants and how Tri-Oxy® ozone water treatment systems like the Tri-Oxy® COMPLETE can help you get rid of it once and for all.
All plants, except the heartiest hybrids, are capable of developing mildew. Powdery mildew, in particular, tends to strike in the Summer or Fall months, when nights are humid, and the temperature lingers between seventy and eighty degrees. Although it isn't shaped like your run-of-the-mill mushroom, it's a fungus that spreads through spores, just like any other fungus.
The spores travel through the air and settle on yard plants. They only grow and spread when conditions are favorable, meaning warm and dry weather. If the conditions aren't perfect, the spores can linger in buds until conditions change, sometimes even overwintering and appearing during warmer weather.
Powdery mildew describes a variety of different types of fungus, all with a similar appearance. Each type is white or gray in appearance and looks a lot like powdery dust. Plant owners typically notice it once it has begun to cover the leaves and stems, but it can cover every part of a plant, including flowers and fruiting structures.
The good news is that the fungus responsible for powdery mildew is host-specific. This means that mildew growing on one variety of plants will not spread to a different variety, even if it's growing nearby. Even so, it's still bad news for the infected plant.
Just like the fungus in your shower tiles, powdery mildew is not fatal, but that doesn't mean that it belongs on your plants. In addition to being generally unattractive, it causes unnecessary stress for the plants themselves. If the infection gets needlessly severe, it can weaken the plant, leading to insect damage or other infections and diseases.
Fungus on a plant functions similar to a parasite. It uses the plant's nutrients to grow and spread. This includes the sunlight.
If the fungus covers enough surface, it can compromise a plant's ability to undergo photosynthesis, and leaves will become discolored or drop off. This is especially detrimental to plants.
In the case of fruits and vegetables, the fungus can affect nutrients and sugars in the fruiting bodies. This can affect their taste, color, and nutritional value. Often, plants infected with a significant infection become inedible.
In essence, powdery mildew is not fatal to plants, but it's harmful and diminishes their aesthetic and nutritional value. Therefore, if you notice signs of powdery mildew on your plants, it's best to pursue appropriate treatment.
There are a few simple steps to take right away if you notice a powdery mildew infection on your plants. First, you can begin by cutting away any leaves that show signs of infection. This will keep the spores from spreading to other parts of the plant, which will keep the infection from worsening.
You will also want to stop applying fertilizer to the infected plant. This only provides more sustenance to the fungus and can cause the mildew to spread quicker. You can resume fertilization once the fungus is under control.
While you can't prevent it from raining on outdoor plants, it's best if you can temporarily avoid watering your plants from above. The extra water can also encourage mildew spread.
When treating powdery mildew, your first impulse might be to use chemicals or fungicides. While this might be effective at eliminating the mildew, it does not solve the problem of sparing your edible plants. There are more natural treatment options that will not affect fruits, vegetables, or other plants.
The Tri-Oxy COMPLETE is one such option. It is not a fungicide but an intelligent ozone water generator that uses ozonated water to kill mold and mildew. It mixes your existing tap water with ozonated gas to create a natural solution that not only eliminates mildew but leads to increased health and growth.
Ozonated water is a biocide. It functions as a sanitizer that can sanitize both organic and inorganic surfaces. Essentially, ozone is oxygen in an activated state that can break down pollutants. When the ozone interacts with water, it creates a chemical reaction. When the solution interacts with plants, it releases oxygen, and all the powdery mildew becomes oxidized.
Ozonated water is food-safe and environmentally friendly, making it a better option than chlorine or other chemicals. It can eliminate mold and mildew on plants in as little as two minutes of contact time. In addition, regular misting can eliminate current fungal infections and prevent future infections.
Ozonated water created through the Tri-Oxy COMPLETE system will not kill live insects, so your pollinators will remain safe.
Ozonated water is part of my regular routine at home. I use it when I wash my produce and when I care for my plants, and that habit has made me a more observant gardener. When you rinse and handle your own fruits and vegetables yourself, you get familiar with how they normally look, and a change tends to stand out sooner.
Before I knew about ozone, my vegetable rinse relied on a diluted chemical sanitizer. Switching to ozonated water took that chemical out of my kitchen entirely, and the same water now serves double duty for my plants.
I also do my homework before I change how I water or wash anything. I have spent hours reading the crop research on ozonated water, because I want to understand what the studies actually show before I rely on a method in my own garden. That is why a sanitation-first routine is what I choose for my own water, my own produce, and my own plants.
You put a lot of work into your plants, and a little fungus shouldn't be enough to derail your effort. Why not fight a natural pest with a natural sanitizer? Ozonated water is an all-natural oxidizer that will not only eliminate powdery mildew, but it will also make your whole garden heartier and healthier.
You can purchase the Tri-Oxy® COMPLETE Water Ozonator online and begin to treat your plants immediately. To learn more about the power of ozone, explore the Tri-Oxy® Refresh Ozone Diffuser & Degassing Kit and purchase your Ozonator today. Your garden will thank you!
Each type of powdery mildew is white or gray in appearance and looks a lot like powdery dust. Plant owners typically notice it once it has begun to cover the leaves and stems, but it can cover every part of a plant, including flowers and fruiting structures.
It tends to strike in the Summer or Fall months, when nights are humid and the temperature lingers between seventy and eighty degrees. The spores travel through the air, and if conditions aren't right they can linger in buds until conditions change, sometimes even overwintering.
Yes. The fungus responsible for powdery mildew is host-specific, which means mildew growing on one variety of plants will not spread to a different variety, even if it's growing nearby.
Begin by cutting away any leaves that show signs of infection, stop applying fertilizer until the fungus is under control, and temporarily avoid watering your plants from above so the extra water doesn't encourage the mildew to spread.
Ozone is oxygen in an activated state that can break down pollutants. When ozonated water interacts with plants, it releases oxygen and the powdery mildew becomes oxidized. It is food-safe, environmentally friendly, can eliminate mold and mildew in as little as two minutes of contact time, and will not kill live insects, so pollinators remain safe.
Published December 30, 2022 • Updated August 27, 2026
By Eileen Durfee, inventor of the Tri-Oxy® ozone water systems.
Educational notice: The information here is shared for general education about plant care and ozonated water. Creatrix Solutions products are not intended to diagnose, treat, cure, or prevent any disease. Individual experiences vary, so let your own results in the garden guide you, and bring any questions about your health to a qualified healthcare professional.
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