Home Improvement Expert Danny Lipford

How to Control Powdery Mildew in Your Yard

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powdery mildew on camellia

Powdery mildew happens to even the most carefully tended plants – seemingly out of nowhere, prized ornamental plants and lawns get a fuzzy gray coating that reminds you of that container you pulled out of the back of the fridge. Powdery mildew isn’t immediately fatal, but it can cause considerable stress to your plants. Fortunately, you can control it in a few easy steps, and here’s how.

About Powdery Mildew

The term “powdery mildew” actually refers to an entire group of fungi, each one attacking different types of plants. It usually starts with a few round white or grayish spots that you can rub off with your finger. They spread and join until the entire top leaf surface is covered, then it moves on to the underneath, stems, flowers, and fruit.

As powdery mildew takes over, photosynthesis becomes very difficult for the plant. This can cause growth of the plant to slow and distort, leaves to fall, and flowers and fruits to fail to form properly.

Powdery mildew can affect any plant, but lilacs, roses, fruit trees, vegetables, begonias, and lawns are particularly susceptible. Since the fungi are species specific, powdery mildew on your fruit trees won’t spread to camellias or other plants.

Conditions Favorable for Powdery Mildew Growth

Powdery mildew thrives in dry weather with high relative humidity. Unlike other fungi, it doesn’t like rain or extreme heat, and it tends to slow when temperatures soar over 90° F. Powdery mildew needs a dry leaf surface, moderate temperature, and high humidity to form. These conditions are often caused by:

  • Seasonal weather: A summer that combines drought with high humidity is an invitation to powdery mildew.
  • Crowded plants: Densely packed plants, overgrown shrubs, or plants under trees, are more susceptible to powdery mildew due to poor air circulation and cool, humid conditions.
  • Overfeeding: Lush, succulent growth caused by over fertilizing is particularly susceptible to powdery mildew.

How to Treat Powdery Mildew

Powdery mildew may seem to spring up faster than you can control it, but the good news is that it’s easy to treat and not immediately fatal. Take these steps to treat powdery mildew on your plants:

  • Prune: Cut off affected growth, prune the plant to open it up to more air circulation, and trim back tree limbs that might be shading too densely.
  • Disinfect: Clean pruning tools in a bleach/water solution to kill any remaining spores.
  • Neem oil

  • Clean Up: Pick up all fallen leaves and pruning debris and put either in the trash or in a hot compost pile.
  • Stop Fertilizing: Reduce nitrogen fertilizer in order to slow down succulent growth.
  • Spray with Water: If plants are in the sun, try washing the patches off the leaves with a spray of water. Avoid extra water in shady or damp areas.
  • Spray with Fungicide: If all else fails, spray plants with an eradicating fungicide. Check the label to make sure it’s rated both for powdery mildew and for your plant type. Natural treatments include neem oil, copper, and potassium bicarbonate. Use chemical fungicides only as a last resort.

How to Prevent Powdery Mildew

Of course, the best way to treat any plant disease is to avoid it in the first place! Try these steps to keep powdery mildew from taking over your yard:

  • Choose Resistant Plants: Some varieties of plants are more resistant than others – check the plant labels before you buy.
  • Focus on Air Flow: When planning your garden, make sure that all areas have adequate air circulation and that plants are adequately spaced. Thin or prune plants and trees as necessary to prevent stagnant, humid corners.
  • Grow in Sun: Whenever possible, orient your planting beds so they get at least a few hours of sun each day.
  • Use Preventative: If powdery mildew is a problem in your yard, spray your plants with preventative fungicides to keep it at bay. Natural preventatives include sulfur and baking soda. For an easy homemade preventative spray, mix a spoonful of baking soda and a spoonful of either dish soap or horticultural oil (such as neem oil) into a gallon of water. Don’t overuse the spray – you don’t want to the baking soda to build up in your soil.
  • Spray Regularly: Apply preventative sprays every couple of weeks.
  • Vary Plantings: Since the fungus is species specific, reduce infection of your annual plants by rotating the varieties of plants each year.
  • Water Wisely: Water in the morning to allow plants to dry. Use soaker hoses and drip irrigation, rather than overhead sprinklers, to reduce humidity around your plants.
  • Don’t Overfeed: To keep growth in check, use balanced organic fertilizers and compost, rather than high-nitrogen chemical fertilizers.


Please Leave a Comment

3 Comments on “How to Control Powdery Mildew in Your Yard”

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  1. AUDREY CLIFT Says:
    July 17th, 2012 at 7:14 pm

    THE INFORMATION IS USEFUL ON FUNGUS INFECTIONS, AND I AM CURIOUS IF THIS IS SPREAD BY (SHOE CONTACT) WALKING THROUGH AREAS INTO AREAS WHICH AREN’T CURRENTLY AFFECTED?

    THANK YOU SO MUCH!!

  2. Arlene Says:
    February 20th, 2014 at 2:42 pm

    Since I just discovered the powerdy mildew on the underside of my camelias is it too late to save the plants? The underside is almost covered. Should I prune all the branches off to promote new growth. I saw a remedy using
    2-3 Tablespoons of apple cider vinegar, is that good? Can I use this as a preventative on healthy plants? If so, how often?

  3. Vinny Says:
    October 8th, 2014 at 11:14 pm

    Here’s something to think about. I bought a used lawn tractor. It had a bad break so this year I fixed it. To do this, the mowing deck needed to be removed. While it was off, it was a good time to sharpen the blades and clean the underside. It was loaded with dead grass and much had a powdery white dust all over it. I got really dirty cleaning it and know I breathed in some dust. Its 2 1/2 wks later and I just spent 3 days in the hospital, VERY sick. Diagnosis: Fungal pneumonia. Possible? You tell me. I only offer this as an act of kindness to everyone. Yes it was my fault, but learn from my mistake. Oh, and companies that do lawn service do pick up fungus at one house and transfer it to the next. Thanks, Vinny
    I’m open for opinions, that’s how we learn.

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