HOW-TO: Prevent & Treat Powdery Mildew
OK, let’s talk about powdery mildew on squash plants.
One day during my daily plant inspections, checking for bugs and such, I noticed some powdery mildew on my squash plants 😱. At first, I freaked out, but after doing some research, I learned it’s not that bad (if caught early), and it’s fairly easy to treat!
How to prevent powdery mildew:
Zucchini plant pre-powdery mildew.
Do not overcrowd your plants.
Garden planning is so important. This being my first "real" garden combined with my stubbornness, I loosely followed a garden bed layout. Lesson learned I will strictly follow one this Fall. Make sure to space your plants out MORE than recommended. You’ll thank yourself later.
Air Circulation
Proper air circulation is very important in preventing mildew and other plant diseases from developing. In California, we’ve been having a long-stretches of heatwaves & high humidity even leading into the fall, combined with smoky air conditions due to the wild files which create perfect conditions for mildew to grow.
CORRECT WATERING
Water at the base of your plants. Avoid getting any leaves wet. This will not only help to prevent mildew but other common diseases and leaf burn. I prefer to water my plants in the early morning so leaves have time to dry before the sun gets too hot.
Don’t overwater. Let the top two inches dry out in between watering. If you're not sure when to water, I highly recommend purchasing a moisture meter. It’ll be the best $10 you’ve spent!
Prune and dispose of infected leaves, stems, and debris.
Remove any dead or yellowing leaves, and I also prune to increase air circulation within my garden beds. Clean debris in and around your garden beds.
GROW VERTICALLY
Set up vertical trellises for squash varieties. This not only helps with watering but creating air circulation, and it also helps the bees get in there easier to pollinate!
My DIY vertical trellis for my cucumbers, watermelon, and zucchini.
How to treat powdery mildew
The sooner you respond, the more likely you’ll be able to control powdery mildew.
Powdery mildew on pumpkin plant.
Organic Fungicides:
If you prefer something pre-mixed, there are many fungicide options available. I use all three of these brands for pest and disease control.
Make your own fungicide solutions:
Apple Cider Vinegar (ACV)
Mix 2-3 tablespoons per gallon of water.
Do a leaf test first to ensure the solution is diluted enough and doesn’t cause leaf burn. Once everything checks out, spray the tops and bottoms of leaves every few days or as needed.
Milk Solution
Mix a 40% milk/60% water solution and spray all leaves every 7-10 days.
Baking Soda Solution
mix 1 teaspoon of baking soda per quart of water in a spray bottle. Use as a preventative and treatment for early outbreaks. Spray every 7 days.
If the plant becomes overwhelmed, consider removing the entire plant to prevent spreading throughout your garden. Diseased plants are more susceptible to pests and other diseases.
How to identify powdery mildew