Powdery mildew is a common disease that affects most squash varieties as well as other plants. It can quickly spread if not properly managed and can be a major headache and a huge discouragement for first time gardeners, as it can potentially ruin crops.
So how do you get rid of powdery mildew naturally? To get rid of powdery mildew without the use of harmful chemicals, you can spray a neem oil/water mixture on the leaves
However, the best thing you can do is prevent it from happening in the first place. Here are some tips:
Prevention
Aphids
These are the little bugs are the most common carriers of the disease and this is why it’s important to prevent an infestation as early as possible. So, how do you protect yourself against aphids? Well, aphids are literally everywhere, even inside greenhouses. This makes them a difficult problem to manage, however, usually an organic approach using lady bugs, neem oil spray mixture and/or other soap sprays will do the trick.
Moisture
Another thing we can do to prevent a powdery mildew infection is to avoid watering the leaves of the plant and only water the ground. I know it sounds simple enough but you’d be surprised how common it is for first-time gardeners to just water the whole plant.
The reason we want to avoid this is because one of the biggest causes of powdery mildew is moisture. It’s one thing to have aphids carrying the disease over to your garden, it’s another thing to provide the perfect environment for them.
Powdery mildew loves to grow in environments with lots of humidity and average temperatures. Sometimes even overwatering can cause humidity and moisture to build up underneath and around the plants, especially squash and other gourd plants, since their huge leaves can create a microclimate underneath them. Greenhouses can also provide a perfect environment for the spread of the disease.
So making sure that your plants have adequate airflow is very important to regulating the temperatures and prevent the growth of potential disease such as powdery mildew.
Understanding the Cause and Considering What To Grow
So, what actually causes this nasty garden disease?
Powdery mildew diseases are caused by many different species of fungi, with Podosphaera xanthii (a.k.a. Sphaerotheca fuliginea) being the most commonly reported among most gardeners.
The thing with powdery mildew is that some vegetable plants are more susceptible to it than others and for an interesting reason, too. Some plants only have one type of fungi that can cause the disease.
For example, the fungi that causes powdery mildew on apple and pear trees is called Podosphaera leucotricha and the fungi that causes it on grapes is called Erysiphe necator (or Uncinula necator).
Unfortunately, squash, melon and other gourd plants are the most susceptible to powdery mildew infections, due to the fact that multiple types of fungi can cause powder mildew in gourd plants.
I know. It’s a sad realization that I had to come to terms with also.
Hey! That does’s mean that we should give up on growing squash, pumpkins, watermelon or any other plants in the gourd family. There are ways to help minimize and prevent powdery mildew from spreading further along in your garden.
Already Infested?
Okay, you’re probably here because you already have the disease and it’s too late for preventative measures. Here’s what you do:
- The first step is to get rid of all the parts on the plant that are infested. Every leaf and stem that you see has this infection has to go and make sure you are not only looking on the top of the leaves but also on the bottom sides as well. Getting rid of the problem is key to preventing a re-infestation of the disease from coming back. If you feel your infestation is too large for a simple pruning, then you might have to get rid of the infected plants all together.
- If the disease hasn’t spread to all parts of the plant and is just getting started then we recommend using a neem oil spray mixture or using other soap sprays. Personally, I highly recommend the neem oil spray mixture as it has shown excellent results in halting the disease and preventing the return of it.
What is Neem Oil?
Neem oil is an extract from the fruits and seeds of the neem tree (also known as the nimtree or Indian lilac) which is an evergreen tree native to India. It’s known to have anti-fungal and pesticide-like qualities.
This was first observed when it was noticed that the lotus, who would normally consume all vegetation in sight, would avoid the vegetation of the neem tree. Scientist later extracted the oil as they would any other vegetable oil and people now use it as an organic pesticide for home garden use.
So not only is it great for controlling disease such as powdery mildew but it can also act as an organic insecticide to prevent aphids and other pests from spreading diseases in your garden in the first place.
Need oil is also great, once you have quarantined an infection, to prevent an infection from coming back and reinfecting your plants.
However, you can’t just use neem oil directly on the plants, you have to dilute it first, usually with water and a safe to use soap. I’ll show you the exact formula that I use in my garden.
The Neem Oil Formula
As mentioned above, neem oil is great for preventing diseases such as powdery mildew from spreading (along with our other tips). However, if you already are have an infection and are trying to avoid spraying harmful chemicals in your garden, then neem oil is also a great choice.
So, enough talk, what’s the most effective neem oil mixture? Well, I’ve found that a good 50/50 ratio of neem oil to soup suds works best.
Here’s what you’ll need to make a 1 gallon mixture of the neem oil spray:
- 2 tablespoons of Neem Oil – make sure that you choose an organic cold-pressed oil, like the one listed on our resources and tools page.
- 2 tablespoons of Sal’s Soup Suds – This is the cleanest and safest soup that you can use.
- 1 gallon sprayer bottle – fill the sprayer with 1 gallon of water
Optional: You can add some essential oils such as Rosemary, Clove, Peppermint, Cilantro which also can have anti fungal properties which act a bit faster than the neem oil and give time for the neem oil to do it’s work. However, neem oil alone should work just fine. If you decide to add some, just 5-10 drops of your choice of essential oils will do the trick.
Of course you can just take the formula above and just mix it all together right into the sprayer.
However, to get a good even mix, I found that the easiest way to make this mixture is to start off with filling up a small 16 ounce plastic bottle then add the 2 tablespoons of the neem oil and 2 tablespoons of the Sal’s Soup Suds and shake vigorously to get a nice thick milk-shake like consistency.
Pour that mixture you just made into the gallon sprayer and then fill the remaining space in the sprayer with water, up to the 1-gallon mark.
Give the sprayer a good mix and you’re ready to spray down any infected areas where you see the powdery mildew but also don’t forget to check under the leaves for infections that you might have missed. It’s always a good idea to spray neighboring plants, even if they’re not infected, to prevent those plants from getting the infection in the first place.