Powdery Mildew on Plants

Powdery mildew is the bane of my existence every growing season living in a humid climate.  It is a fungal infection that covers the plants leaves, stems, and fruit.  If left untreated, it can lead to poor production, yellowing leaves, and can even cause your plants to die. 

So, how do you identify powdery mildew and what can you do about it?

Identifying Powdery Mildew  

Anyone who has heard of or experienced powdery mildew may be a bit paranoid about their own plants.  This is understandable since it can take a plant out entirely.  However, it is important to note what is actually powdery mildew and what is not. 

What do I mean by that?  Powdery mildew most commonly affects squash and melon plants.  Of which, some plants have a silvery color to their leaves that is normal.  However, it can look like powdery mildew to the suspicious eye.  

So how do you tell the difference?  Leaves that are silvery by nature tend to have a specific pattern.  Some are less obvious than others but if every leaf has a matching pattern, then that is not powdery mildew.  Check out my short video on my squash plant that has a silvery pattern. 

If a plant has powdery mildew it will be fairly obvious because it will coat the entire leaf.  If you let it progress, it will coat the stems and then the fruits.  See what powdery mildew looks like in this video on another squash plant. 

Prevention

The first best way of dealing with powdery mildew is taking measures to prevent it from happening.  Moisture is the leading cause of this fungal infection.  Therefore, keeping plants well trimmed and spaced apart to provide proper airflow is key.  

Now, this doesn’t mean for you to go wild and cut every leaf off.  Those leaves serve as protection for the fruit the plant is growing.  Try to keep leaves that cast shade for fruit and clear away others that are not serving a true purpose.  Remember that leaves are also a defense mechanism against animals, so you may need to substitute with a different type of barrier. 

Next is making sure to only water around the base of your plants.  This keeps excess moisture away from your leaves.  You may even try watering only in the morning depending on your climate.  That way, if any water does land on the plant, it will dry off with the heat of the sun.  

Treatment

Even if you take measures to prevent powdery mildew, it is bound to happen at some point.  So let’s talk about how to fix that problem.  Note that as we talk about these methods of treatment, they can also be used as methods of prevention by using them as a weekly application.   

You know I only treat organically, so first up is a kitchen staple you likely have on hand, milk.  Mix up milk and water in a spray bottle, a 1:2 part ratio (milk to water) has done well for me, and spray on the entire plant. 

Our tried and true neem oil isn’t just for insects, it can also help treat and prevent powdery mildew.  Remember, this is a night time application to be sure it does not burn your plants in the sun.

Lastly, remove the infected portions of the plant.  Again, your plant needs protection from the sun and animals. However, the easiest way to be rid of this problem and prevent spreading is to cut it off at the source.