If you’ve been gardening for a while now, you’ve probably encountered powdery mildew. Since it affects over 10,000 different plant species worldwide odds are you want to know how to get rid of powdery mildew on plants.
In addition to destroying your crops and fruits, these it makes beautiful flowers and foliage plants look ugly thanks to the white or gray layer of dandruff-like specks that engulf the leaves then the rest of the plant.
So, in this guide, I’ll take an in depth look at powdery mildew, where it comes from what causes it and the symptoms you want to watch out for.
Finally, I’ll show you how to get rid of this nasty plant disease without having to resort to chemical-laden commercial pesticides.
What is Powdery Mildew?
Powdery mildew is actually a disease that can be caused by many fungi species, although these fungi all come from the Erysiphales order.
From its image, you can probably guess where the disease gets its name. It looks like someone sprinkled a whole lot of baby powder onto the leaves of the plants.
While they look like talcum power, these tiny white spots are actually fungal spores and threads.
Its looks is also a bit misleading as many gardeners will initially thing that it is just dirt or dust that has collected on the leaves. But, once you try removing it with your fingers, it just won’t go away.
What Causes Powdery Mildew on Plants?
Another interesting thing about powdery mildew is that it is more prevent during dry, warm climate.
Additionally, low light and humidity encourage its growth as well.
As such, they become more prevalent during late spring to early summer when the nights are still a bit cool with good humidity and the days are getting warmer and drier.
This is the main feature the distinguishes powdery mildew from many other fungal infections, which thrive in moist or damp conditions. In fact, water actually kills the fungal spores that cause powdery mildew.
Instead, these spores rely on humidity which is moisture in the air to germinate. As such, the combination of high nighttime humidity and low daytime humidity is when they grow the fastest.
Similarly, moderate to temperatures that run between 70 to 80 degrees Fahrenheit is where powdery mildew does best.
Because the fungus that cause powdery mildew thrives in crowded plots, it is a good idea to keep proper plant spacing. This not only allows the plants and its roots to expand as it grows but also lets enough air circulate to help prevent powdery mildew.
Sufficient lighting and water are likewise important. Together, the right conditions allow the plant to be healthy which in many cases lets it recover against the infection on its own. The stronger the plant is, the more likely it will be able to do this.
In contrast, a stressed out plant or one that isn’t getting its desired living environment is more prone to getting the disease and succumbing to it.
How Does Powdery Mildew Damage Plants?
Powdery mildew is cause by fungi. And, there are many different fungus that can result in this disease.
However, one of its unique features is that it needs it host to stay alive.
As such, powdery mildew don’t try to kill your plant like most diseases or pests. Or at the very least, keep it alive for a very long time.
So, in most cases the disease is not fatal. But, it does make your plant look sick and abnormal.
This also gives the plant a chance to recover if the conditions that caused the problem are corrected. Although it needs time to recover to do this.
However, you never want to allow the infection to become severe.
That’s because it will require a lot of help from you, including treatment as well as correcting the environmental conditions to recover. Without your intervention, the plant will eventually succumb to the powdery mildew.
As the mildew keeps blocking light from the sun and absorbing its nutrients, the host will get weaker and weaker. When it gets to this point, you’ll see yellow leaves that are wilting and withering.
Since they affect fruits and vegetables, these will also look unwell such that no one will want to eat them. They’ll also lose their flavor.
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Symptoms of Powdery Mildew
Dusty layer of white or gray powder-like substance on its leaves and stems.
While this is the easiest way to spot it, it also means the disease is already spreading. That’s because powdery mildew tends to start at the undersides of leaves.
As such, like checking for other diseases and pests, you always want to lift the leaves and check the bottom sides for problem signs.
Powdery mildew also does not limit itself to leaves, it will cover the flower, fruit and stems as well.
Eventually, it will cause the plant’s leaves to drop, wilt and change color (yellow, brown and black).
One of the reasons the plant will keep deteriorating is because the more the mildew covers the leaves, the less light they’ll be able absorb. This will reduce their ability to produce their own food and energy via photosynthesis ultimately weakening the plant.
Plants Affected By Powdery Mildew
Most plants can be affected by powdery mildew. The only exception are gymnosperms, which include seed producing plants like conifers, cycads and gingo. In contrast, angiosperms or flowering plants can be affected by powdery mildew.
The same is true for many fruits and vegetables.
Here’s a brief list of some plants. Note that the list is not comprehensive.
You Can Use Commercial Fungicides If You Want
One option to get rid of powdery mildew is to use commercial fungicides. This works, but like their pesticide counterparts I prefer to avoid these products unless you know exactly what the ingredients are and how they can affect you and your garden.
One important thing to know about powdery mildew is while it can look scary because of the white layer covering your plant’s foliage, it is a mild problem.
As such, it can actually resolve on its own without having to use fungicides.
As long as you take care of it properly and allow it to get sufficient airflow, it will go away on its own as the weather changes.
That said, there are some severe cases where it starts spreading and affecting other plants. if that starts to happen, you need to take action immediately.
If you want to use commercial fungicides, I suggest going with organic ones. These are less toxic and cause less problems.
Another option is to do it yourself with more natural ingredients.
How to Get Rid of Powdery Mildew
in this section, I’ll go through some effective ways to get rid of powdery mildew without having to use commercial fungicides.
One of the reasons I went through all the sections above before coming to the treatment section is that those sections help you understand what causes powdery mildew and how it spreads.
Those conditions also hold the key to knowing how to get rid of it.
One of the most important things you can do is to improve air flow. This will help get rid of powdery mildew without using fungicides. By giving plants enough space, more air can circulated to help improve their living conditions.
The right amount of sunlight also helps a lot. Fungal disease thrive is darker or low light conditions. As such, more sunlight will help get rid of powdery mildew.
Watering the plants directly on the soil instead of overhead also recues infection and disease. For one, you don’t have to worry about wet leaves that don’t dry. It also increases humidity which promotes fungal problems.
Milk is most effective during the early stages of infection. Depending on how much powdery mildew there is, the concentration of milk to water can vary from 1:10 (milk to water) all the way up to 1:1 where you have equal ratio of milk and water.
The latter is reserved for severe cases, which the former is enough if you spot powdery mildew fairly early.
Mix the two ingredients and put the solution in a spray bottle. Then, apply to the leaves making sure that you get the undersides as well. It will take applications of 2 times a week for a few weeks to see results.
If you want something more potent that milk, neem oil is a good choice. This is natural spray remedy you can get from stores.
Neem oil comes from the neem tree. But, you’ll want to mix it with water because on its own it is too potent. Thus it will cause leaf burn if not diluted with water.
Mix about 3 tablespoons of neem oil with one gallon of water into a spray bottle. Some people like to wipe the leaves with the solution.
You’ll need to spray the plant’s leaves once every 7 to 14 days until the powdery mildew goes away.
Vinegar is an awesome home remedy because it can be used in so many ways.
Powdery mildew is one of those things. For this, apple cider vinegar is the best kind of vinegar thanks to its acetic acid content. You want something with 5% concentration to be effective.
But be careful with using too much because it will burn the plant’s leaves. Diluting with water will help reduce its concentration.
You can use a ratio of 4 tablespoons of apple cider vinegar with 1 gallon on water. Apply once very 3 to 4 days until the mildew is completely gone.
Potassium bicarbonate can be mixed with soap and water to get rid of powdery mildew. It limits the growth of fungus by making the environment unideal for them.
- Combine 3 tablespoons of potassium bicarbonate with half a teaspoon on soap and 3 tablespoons of vegetable oil.
- Dilute with a gallon of water and place in spray bottle.
To apply, spray the mixture on the plants that are infected.
Baking soda is also known as sodium bicarbonate. Note that this is different from potassium bicarbonate.
Combing 1 tablespoon of baking soda with half a teaspoon of dish soap. Then add one gallon of water.
Mix properly in a spray bottle then apply on the leaves.
Sulfur is a common type of fungicide that’s been used for powdery mildew. However, it is most effective as a preventive measure. So, you want to use it before symptoms start coming out on plants that are highly susceptible to the infection.
You’ll find two kinds of formulations for this. One is dust/powder form which you can dust on the affected plant. Or, you can use it in liquid form via a spray bottle.
Make sure to follow the instructions on the bottle and use proper protection. Gloves, safety goggles and a face mask are essentials because sulfur will irritate your skin, eyes, nose and mouth.
Another option is to use garlic which contains sulfur. Unfortunately, it is harder to get that much sulfur concentration from garlic. So, you’ll need to use quite a bit of it.
You can create your own DIY garlic solution by combining it with neem oil or rubbing alcohol.
But a better option is to pick up garlic oil from the store which saves you time.
Biofungicides are a lesser known treatment. They use different microbes to get rid or control diseases.
Like some of the other fungicide products, these are available in many different brands and solutions.
The biggest advantage is that they are not toxic and don’t leave residue. Also, powdery mildew is not resistant to these.
Like sulfur, copper is another fungicide that works to get rid of powdery mildew.
It is worth noting that experts believe that sulfur is more effective, at least for powdery mildew.
You’ll be able to find copper fungicides in stores in spray bottle form. This makes it easy to use as all you need to do is spray. Some can be attached to a garden hose to apply.
My Final Thoughts on Powdery Mildew
As you can see there are many ways to get rid of powdery mildew on plants. The best part is, there are many different organic and natural treatments you can turn to instead of using commercial fungicides.
Like all infections, the earlier you catch it, the easier it is for these treatments to remedy the problem. As such, regular inspection is crucial.