Small space gardening, cooking, and crafts
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Powdery Mildew - Commercial vs. Homemade Remedy

Lately, I find that I start out every morning with a cup of coffee and a gaze out upon my balcony garden. Being zen has never been easy for me as my mind races with all of the tasks that lay before me that day. Since I started my itsy garden, however, I have come to realize that those initial moments watching as the morning mist burns away under the first taste of warm sunlight, I am calm. I can imagine doing yoga out there, if only I hadn't filled the space with so many plants. Tomatoes, cucumbers, basil, peas, peppers, strawberries... wait a minute. What in the world is wrong with my strawberries?

Was someone eating a powdered doughnut over this plant? Ick!

Gazing around a bit more, it quickly became apparent that the consumption of sugary pastries was not to blame. I was dealing with a plague of powdery mildew.

As this was the first year I attempted to grow strawberries, I wanted to test a variety of types to see which would thrive on my balcony while offering the best flavor:

  • Alpine strawberries seemed like a winning choice as they are ever-bearing, meaning that they will continue to offer their quaint, small berries all season long. Shortly after bringing home a hanging basket, I managed to settle three runners into their own pots with great success.
  • Ozark strawberries are a more common type often found at farmer's market or your local store. They tend to produce in one big harvest, though often fail to fruit until the following year. Only one of my Ozarks offered strawberries so far, and though small, they are incredibly sweet and delicious. Surprisingly, one of the non-fruiting Ozarks has given off so many runners this season (while growing like a crazy itself), that I might have to produce a vertical planter for use next year.
  • Hawaiian Strawberries, also known as Pineberries, were my wild card pick from a local nursery when their supplier failed to get in a different variety of Alpines that I had ordered. These berries are unique in that they do not develop the typical red hue, instead presenting with unassuming white flesh and tiny reddish seeds. Their taste is also unusual in that they are reminiscent of pineapples (thus the 'Hawaiian' in their name as they are not, in fact, from Hawaii). Sadly, I can not attest to the taste as these were my culprit plants and have yet to bear fruit.

All three of my Hawaiian Strawberries developed the mildew at the same time, and fortunately, did not spread it to any of my other plants. While powdery mildew may look similar on a range of plants, there are actually several different varieties that will each attack a preferred crop. While the strain of powdery mildew I dealt with was not likely to jump to my tomatoes, cucumbers, etc, the other two types of strawberries could be in danger.

I returned to the nursery from where I purchased the Hawaiian strawberries and explained their condition. As powdery mildew is treatable, and I had already established the plants within my garden, I wanted to try to treat them, rather than return them even though these plants were likely the originating source of the mildew. I was instructed to use a specific commercial spray after the plants' next watering that was listed as safe for organic gardens.

It took nearly half the bottle to treat and protect all of the strawberries in my tiny garden with this picture showing the results two days after spraying. The product did manage to remove some of the mildew, but a second application days later showed no further improvement. Though the commercial spray listed a number of plant diseases that it should be successful in treating, including several types of powdery mildew, it would seem that my particular strain was not a good match.

Though the crowns were healthy and producing new leaves, any established greens were suffering beneath the leeching mildew. Rather than fan out like little solar panels, the leaves were curling up and browning at the edges, which would eventually rob the plant of necessary sunlight. With the commercial spray a bust, I turned to the helpful folks at www.growingformarket.com

Their article on powdery mildew offered an interesting option for using 1 part cows milk to 10 parts water. I will admit to having read this article before visiting the nursery and thought it was just too simple of a solution, similar to those articles claiming that a random kitchen ingredient can do absolutely everything. I love vinegar, baking soda, coconut oil, etc, but let's be honest, none of those can do my taxes. Watery milk as a solution to powdery mildew just seemed unlikely, especially when the commercial spray had already failed to fully remove the mildew.

I really had nothing to lose though. My plants needed help and if watery milk could save them, it was such a small amount of effort that I would be foolish not to try.

If I use 2 cups of water, how much milk do I..... fractions, grrr. If you aren't familiar with ounces by now, do a meet and greet for this project. 10 ounces of water, 1 ounce of milk then double or triple as needed for the number of plants. I made enough to fill half of my sprayer, and ran out -but- don't be temped to make a huge batch. This is still milk and unless you intend to refrigerate the sprayer, just make more as needed.

Take your sprayer out to the affected plants and cupping the leaves in your hand, spray generously. Once assured that all areas are coated, gently turn the leaf over and spray the underside. Powdery mildew is sneaky and will hide anywhere that is green, so don't hold back. You might even knock out your mildew issue in one application if you soak every spot properly.

So how did the watery milk work for me?

This was, by far, my worst plant. The watery milk completely eradicated the mildew on the first application, leaving leaves that are damaged and discolored, but alive. New leaves have bloomed from the crown and remain mildew free. Once the plant has a healthy new crop of leaves, I'll start removing the damaged ones.

Another shot of the same plant with a runner that was especially covered in mildew. I'll remove the curled leaf if it doesn't flatten like the other two.

Another example of how the powdery mildew causes leaves to use curl up, taken a couple hours after applying the watery milk solution. All of my runners were showing signs of leaf curling.

Three days after the watery milk solution and the leaves on this plant were flat and healthy. Within a week, all plants had new, mildew-free leaves allowing me to remove the damaged ones.

Two weeks after I applied my first round of watery Milk, 90% of my strawberries and runners remained mildew free. One of the three original plants proved to be a bit more stubborn and required a second spray to completely remove all of the mildew, likely on account of a some shading from a nearby tomato plant.

So there you have it. In a showdown between the $10.00 commercial spray vs. $.05 watery milk solution, the homemade remedy was not only cheaper and but more effective for my particular type of powdery mildew. To be fair, the plants were all initially treated with the commercial spray, but the amount of mildew it removed was similar to that removed by water misting. 5 days after the commercial spray, the mildew saturation had returned to previous levels and appeared undeterred. The plants were watered in a similar fashion prior to the milk spray, which did result in the removal of mildew on nearly all leaves. Milk was simply the winner for this type of powdery mildew.

Prior to spraying the milk solution you might hesitate and wonder 'won't this smell awful in the heat?' As my balcony has a roof that prevents rain, I was concerned, but threw caution to the wind and sprayed with reckless abandon. Worst case, I would have to waterfall a few buckets of water over the floor and do a little scrubbing. Surprisingly, there was no smell and no visual sign that milk water was ever sprayed on the pots, boxes or floor. All the same, treat this as you would your carpet and spray a test patch in an unseen area just to be absolutely certain that the milk solution won't stain your finish.

While it is my hope that you never encounter powdery mildew, at least there is an cheap and easy solution for this all too common garden problem.

Happy planting!

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This article's still images and text by Sandra Rosner are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

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