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How do you get rid of powdery mildew organically in your home grow?

prevent powdery mildew in a home grow

If you have powdery mildew in your personal home grow and want to get rid of it organically, then you won’t be using any synthetic fungicides. Rather, you’ll be using organic, natural methods to get rid of and prevent powdery mildew.

First, home growers and caregivers should be aware of what not to use in cannabis cultivation: myclobutanil.

Myclobutanil is a synthetic, man-made fungicide that is easily accessible to cannabis growers simply because it is a common product legally used to prevent powdery mildew on crops like fruit trees, vines, strawberries, almonds, and wine grapes. However, myclobutanil is not safe or legal in cannabis cultivation! Why? The danger with myclobutanil is that once it is heated past 400°F (205°C), it produces toxic fumes — hydrogen chloride, hydrogen cyanide, and nitrogen oxides. The temperature of your average lighter can reach nearly 1,977 degrees Celsius or 3,590.6 degrees Fahrenheit. See the problem? This is a serious health concern and risk to home growers who are not educated about myclobutanil.

Eagle 20 is the most well known myclobutanil product. Eagle 20 or any product with myclobutanil is very dangerous and strictly forbidden in cannabis cultivation and against the law. This goes for home growers and commercial growers. Do not spray any product containing myclobutanil on anything that would be smoked or of which the oil is to be extracted.

There are a number of ways growers and caregivers can organically get rid of powdery mildew.

As a general rule, you’ll want to use multiple techniques, not just one or two. This lessens the potential of powdery mildew becoming resistant to your method.

Maintain a Safe Humidity

Keep a close eye on the humidity level in your grow tent by putting a hygrometer in your grow tent or grow room. Although it is widely known that a humidity of 70% is ideal for plants in veg and 60% for plants in flower, you may want to lower the humidity to 40 – 55% during powdery mildew infestations. This will make it much harder for the powdery mildew to thrive, replicate, and be a pain in your home-grow!

Get Hands-on

Of course, nothing is as organic as using your own hands. So first and foremost, remove any leaves with powdery mildew from plants by pinching the leaves off or by using trim scissors. Just be sure to clean your hands and clean and sterilize your trim scissors afterwards. Removing diseased leaves is a fast and effective way to limit powdery mildew contamination progress in your home grow. If you see even just a small white powdery mildew spot, get rid of it! Remove the leaf, bag it, tie it, and bring it to the trash can on the curb immediately.

Feed Your Bacterial Helpers

Soil growers can strengthen the microbial life in their root zones by adding compost tea or bacterial food like molasses. Compost teas and unsulphured molasses will help support the healthy bacteria and fungi within the soil to help prevent powdery mildew organically. This practice can not only help your plants improve nutrient uptake and produce superior buds, but also boost overall plant health and vigor.

Mix Your Own Solution

Make organic, natural sprays at home that help prevent and control powdery mildew organically. Active ingredients may range from H2O2 to rubbing alcohol, horticultural oil, soybean oil, clove oil, garlic oil, peppermint oil, nettle and horsetail, among others. Apply when the lights are off to prevent any leaf-burning. Some foliar sprays are “contact killers,” which does what it sounds like — kills on contact. Others work as “preventatives” and cover the leaves with a protective covering.

Find an Off-the-Shelf Answer

One of the most popular store-bought organic powdery mildew preventatives is none other than the OMRI-listed Serenade. Serenade is a fungicide made from a patented strain of bacillus subtillis (QST713 strain). Serenade protects against fungal diseases like powdery mildew and blight by stopping such spores from germinating.

Another popular organic powdery mildew preventative is Lost Coast Plant Therapy. Lost Coast Plant Therapy should be applied generously on the tops and bottoms of leaves, on stems and branches, and on the topsoil. Apply when the lights are off to prevent any leaf-burning. Allow plants to dry completely before you turn your grow lights on again. Don’t worry, plants only take about 15 minutes to dry. You may apply it daily during powdery mildew infestations, or 1 – 2 x a week as preventative maintenance.

Sanitize the Air

Lastly, the best thing you can do to get rid of powdery mildew in your home grow is to purify the air — clean the air — yes, sanitize the air! Twenty years ago, the only options were to use ozone and UV systems. Both of these methods have limited effectiveness. Today, air purification can be accomplished via PCO technology, which was developed at NASA and is now exclusive to AiroClean420. PCO stands for Photocatalytic Oxidation (PCO). AiroClean420 uses PCO and purifies and sanitizes air through it. Their PCO units are chemical free and release no ozone or toxic emissions.

AiroClean420 is the premiere PCO provider in North America and has had tremendous success in indoor commercial cannabis cultivation over the past few years, and now offers a home grow unit to help gardeners and caregivers protect their plants with cutting edge technology.


AiroClean420 systems work by using a fan and a bio-conversion reactor bed which contains a catalyst to clean the air. As air is pulled through an AiroClean420 unit and hits the bio-conversion reactor bed, spores, bacteria, and diseases get killed. Not just killed, but completely decimated on the smallest, subatomic level, ten thousand times smaller than the width of a human hair. Further, the bio-conversion reactor bed uses a proprietary light source to ignite the catalyst, and as this happens, Hydroxyl Radicals form on the surface of the catalyst. These Hydroxyl Radicals will oxidize anything organic in the air, with the only by-product being minuscule trace elements of water vapor and CO2. So, there are no harmful emissions whatsoever. Unlike Ozone and UV systems, Hydroxyl radicals produced via PCO are surface-bound and not emitted into the air.

Efficient, Organic, Effective

Although it is possible to control and prevent powdery mildew with organic methods, growers know that it is not ideal to spray your plants with anything at all during plant flowering. AiroClean420 fits the bill and is not only organic but also completely residue-free and clean. Also, each unit works 24/7 – 365 days non-stop. Compared to the other suggestions above, which take the growers time and attention, it is extremely efficient.

There you have it — tips to organically get rid of, kill, and prevent powdery mildew in your home grow. Keep growing and don’t let powdery mildew ruin a crop ever again!

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