Powdery Mildew: Identification, Prevention and Treatment


My first year of gardening, I excitedly bought some Cucumber seedlings after hearing how prolifically they produced. I popped them in my garden beds and over the next few weeks I watched in amazement as they grew like crazy. Then, a few weeks later, I got my very first cucumber. I was over the moon. A few days later I noticed these little white spots showing up on the leaves of the vines. Naive and clueless, I assumed this was meant to happen and left it. Eventually the spots turned into a powdery coating on almost every leaf and so began the demise of my cucumber plants. As a new gardener, it was both discouraging and disappointing to go from so what I thought was going to be my first big garden success to my first big garden fail. I later found out that this powdery white dusting is a disease called Powdery Mildew and is one of the most common plant diseases. It is a particular problem in my area and anywhere that experiences humid conditions but there are ways to combat it so let's take a look.

What is it?

Powdery Mildew is a fungal disease that depletes your plants of nutrients. It shows up on the leaves of plants and looks like a white dusting of powder. As the disease takes over it weakens the plants, causes it to stop producing well and in extreme cases leads to the death of the plant. Powdery Mildew is quite contagious. The white dusting that forms is made up of spores which are then  carried by the wind or insects onto other plants. Powdery Mildew is most likely to occur when soil is dry and the weather is humid.

What does it look like?
Powdery Mildew shows up on the leaves of plants and looks like a white dusting of powder (see photo). Initially it can look like small white powdery dots on the leaves which then spreads over the entire  leaf. 


How to Prevent It

Prevention is always better than cure and  there are things you can do to help prevent Powdery Mildew altogether (although sometimes, depending on the conditions, it is just inevitable):

  • Space your plants well to ensure maximum air circulation
  • Try not to get water on your plants - when watering, water at the roots rather than overhead
  • Spray your plants once a week with homemade fungicide spray (more on this below) or with a homemade milk spray. Milk sprays have been shown to be equally as effective as any chemical fungicide in terms of prevention. A mix of 40% milk, 60% water in a spray bottle and off you go. Spray the underside and the top of the leaves. It is thought that the combination of milk and sun is what makes this successful so it is important to apply the spray during the day when the plants are in sun.
My Go-To Powdery Mildew Treatment
Sometimes it isn't always possible to prevent powdery mildew, so when it rears its ugly head this is my go-to recipe that has given me by far the best results. There are MANY different homemade recipes out there and I think I’ve tried a lot of them. My own variation of The Cornell Method is the one I have had the best result with, so I’m going to let you in on it in the hopes that you will have the same success that I’ve had.
First of all, as soon as leaves start to show signs of Powdery Mildew I cut them straight off and throw them in the bin - don’t compost them.
Then I make a spray using the following:
  •  2L Water
  • 1 Tbs Baking Soda
  • 1 Tbs Coconut Oil (or Neem oil)
 It’s good to use a spray bottle with a wide nozzle as sometimes the solution can get clogged. Once you have made it up, spray all of your plants in the morning or afternoon (not in full sun). Make sure you spray both sides of the leaves. Repeat weekly.

 You may also spot black and yellow ladybugs on   your powdery mildew stricken leaves - they are   friend not foe and feed on the powdery mildew   fungi, so don’t be alarmed if they show up in large   numbers!

 When it comes to powdery mildew, prevention is   always better than cure. Once it has taken hold   you may be able to inch your plants along but its   virtually impossible to get rid of it (in my   experience anyway) but the tips above can help   you both with prevention and damage control!

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