How to Stop Powdery Mildew on Plants, According to a Gardening Pro: Learn About Causes and Solutions

Whether you’re a novice or avid gardener, discovering your greenery is dealing with a disease is never a pleasant surprise. One frequent problem that often pops up during the warmer months: powdery mildew. Since the disease can quickly ruin a gardening season, we asked an expert how to stop it, plant mildew causes and how you can prevent its onset so your plants continue to thrive.

The main causes of powdery mildew on plants

This disease is caused by a group of fungal pathogens, and usually shows up on plant leaves looking like a white powdery substance. Unfortunately, environmental elements can play a part in its formation.

“The main factors that contribute to its development include high humidity, poor air circulation, and shaded areas,” says Tony O’Neill , author of Simplify Vegetable Gardening . “The spores thrive in warm, dry conditions but require high humidity to germinate.”

Another common cause: Overcrowded plants. If there isn’t enough airflow between greenery, it can make the mildew more likely to form and spread between plants.

Finally, a damp environment can be a breeding ground for the fungus. Regular waterings or rainstorms can contribute to this, even if you’re not overwatering.

Why is powdery mildew on plants bad?

Though in some cases powdery mildew is a primarily cosmetic disease, it still has the potential to impact the health of your garden greenery. “It can significantly weaken plants, reducing their photosynthetic ability and overall vigor,” explains O’Neill. “It often results in stunted growth, distorted leaves, and reduced yields in fruits and flowers.”

This means that if powdery mildew shows up early in the garden season, you may not get to enjoy the colorful blooms you were hoping for. Vegetable gardeners may also find that their harvest is shortened or smaller than usual.

How to Prevent Flowering Plants From Fading in Color and Easy Ways to Boost Bloom Vibrancy

For that reason, it’s best to tackle the problem as soon as possible. “It's important to monitor your garden regularly for early signs of powdery mildew,” he says. “Early detection and prompt action can prevent severe infestations."

How to stop powdery mildew on plants

When you notice powdery mildew popping up on your plants, there are multiple steps you should take for proper care. First, remove any leaves that have the substance. “Prune and dispose of any infected leaves or plant parts to reduce the spread of the fungus,” he suggests. This can also help improve air circulation. (Note: If plants are too crowded, you may have to thin those out, as well).

Next, apply a fungicide treatment that’s specifically labeled for powdery mildew. Organic options include sulfur, neem oil and potassium bicarbonate. Just follow the application instructions on the product bottle for the best results.

Can’t find any fungicide spray near you? A pantry staple will help! “A mixture of baking soda and water (1 tablespoon baking soda in 1 gallon of water) can also help control the fungus when applied regularly,” adds O’Neill. (Click through for more uses for baking soda ).

See how one gardener uses a similar treatment of two tablespoons of baking soda in a gallon of water in the video below:

Finally, make sure to water plants at the base rather than overhead. This will help keep the foliage dry and prevent powdery mildew from re-forming.

How to prevent powdery mildew on plants

Worried about the fungal disease becoming a problem in your garden? Preventative measures can be taken to sidestep powdery mildew altogether.

One way to do so: Select resistant varieties. Some plants, like cucumbers, squash, grapes, roses and phlox are particularly susceptible to it. But many species have cropped up over the years that were grown purposely because they won’t fall victim to it. Check to see if the seed packet or plant label says it is “powdery mildew resistant.”

Seed Swap: The Free (and Fun!) Way to Get a Jump Start on Your Garden Right Now

When sowing seeds outdoors or adding seedlings or plants to your garden, be sure they all are adequately spaced. Again, the key here is promoting good air circulation! Removing debris and fallen leaves can make a difference too.

You’ll also want to be mindful of any fertilizers. While they can be helpful in providing your plants with nutrients, the wrong one can increase the odds of powdery mildew later making an appearance. “Avoid over-fertilizing with nitrogen, which can promote lush, susceptible growth,” cautions O’Neill. If your plant becomes too lush, you may have to transplant it to an area with more room or prune some of the branches.

A particularly crucial factor when it comes to powdery mildew prevention: Sunlight! “ Plant in areas with adequate sunlight to reduce humidity levels around the plants,” adds O’Neill. Without adequate sunlight, soil in your garden bed won’t be able to fully dry out between waterings. (Need plants that don't need a lot of sunlight? Find out which are right for you ).

By taking all these steps, you can ensure your garden stays green, healthy and thriving all season long!

For more gardening tips, keep reading!

6 Low Maintenance Plants That Will Thrive in Your Yard, According to Plant Pros

How to Grow Squash Vertically in Different Garden Sizes and Environments, According to Gardening Pros

Gardening Pros Share How to Easily Fill a Raised Garden Bed for Less