Powdery mildew is a common fungus that affects a wide variety of plants. It is easily identified and appears as light grey or white powdery spots usually found on infected leaves, but can also be found underneath, or on stems, flowers, fruit or vegetables. The spots spread and will eventually cover most of the leaves on the plant, with new plant growth being most susceptible.
Powdery mildew thrives in warm, dry climates; however, it also needs fairly high humidity — like the warm days and cool nights in late spring to early summer. Not enough sunlight and poor air circulation also contribute to conditions that encourage powdery mildew.
Although rarely fatal, if left unchecked it can eventually cause serious harm to your plants by robbing it of water and nutrients. Most infections cause minor damage such as leaves turning yellow or becoming withered or distorted, but plants can also become weak, bloom less, and grow slower.
Although most products on the market are targeted more toward the prevention of powdery mildew, there are many home remedies to treat an existing infection. Spray mixtures will only kill what they come in contact with, so be sure to coat all affected areas thoroughly. It may take multiple applications for complete treatment. Apply once a week for three to four weeks, then wait to see results. Reapply as needed.
Autumn sage is a beautiful perennial plant known for its vibrant flowers that come in shades of red, pink purple and white. While these plants add splashes of color to the garden, they are unfortunately prone to powdery mildew, a common fungal disease. Powdery mildew presents as white or gray powdery spots on the leaves, stems, and flowers. If left unchecked, it can weaken the plant and inhibit growth. Fortunately, there are several effective methods to get rid of powdery mildew on autumn sage.
What Causes Powdery Mildew on Autumn Sage
Powdery mildew thrives in warm, humid conditions with poor air circulation The fungal spores are easily spread by wind to surrounding plants Autumn sage is especially susceptible when planted in dense groups with limited sun exposure and airflow. Excess moisture from overhead watering or frequent rainfall also encourages powdery mildew growth. As the disease progresses, the powdery coating spreads and the leaves can yellow, wither, and drop prematurely. It’s important to take action at the first sign of infection to prevent major damage.
Cultural Control Methods
Powdery mildew can be prevented and managed through proper cultural practices:
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Improve air circulation – Powdery mildew thrives in stagnant air. Prune autumn sage plants to open up the foliage. Space plants at least 2-3 feet apart to allow for better airflow.
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Water at the base of plants – Watering from overhead wets the leaves, creating the perfect moist environment for the fungal spores to grow. Always water at the soil level.
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Thin dense growth – Remove some of the oldest and innermost branches that don’t receive much sunlight and air movement. This helps reduce humidity levels around the plants.
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Avoid excessive nitrogen fertilizers – High nitrogen causes rapid, lush growth that is more susceptible to powdery mildew. Use a balanced fertilizer instead.
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Clean up debris – Remove and destroy any infected plant material. Don’t compost diseased leaves as the spores can overwinter. Keep the garden free of weeds.
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Grow resistant varieties – Some autumn sage cultivars have better resistance, like ‘Scarlet’ and ‘Wilder’s Red’.
Chemical Treatment Options
For moderate or severe infestations, you may need to turn to chemical controls. Some effective options include:
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Fungicidal sprays – Look for fungicides containing myclobutanil, propiconazole, or neem oil and follow label instructions. Spray thoroughly on the tops and bottoms of leaves every 7-14 days until the powdery mildew clears
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Baking soda spray – Mix 1 tablespoon baking soda + 1/2 teaspoon liquid soap + 1 gallon water. The soap helps the baking soda stick to the foliage. Reapply every 7-10 days as needed. The alkaline solution disrupts powdery mildew’s growth.
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Milk sprays – The proteins in milk have anti-fungal properties. Mix 1 part milk to 9 parts water and spray plants every 7-10 days to control mild mildew. Use only as a preventative, not for advanced infections.
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Sulfur dust – Sulfur restores the leaf pH balance to combat fungi. Apply according to label instructions. Use caution in high temperatures over 85°F.
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Hydrogen peroxide spray – Mix 1 tablespoon 3% hydrogen peroxide + 1 quart water. Spray the plant’s leaves and stems thoroughly and allow to dry in full sun. Repeat every 7-14 days. The peroxide oxidizes the plant surface to kill fungal spores on contact.
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Potassium bicarbonate spray – Mix 1-2 teaspoons potassium bicarbonate + 1 gallon water. Spray leaves liberally and repeat every 7-10 days. This adjusts the leaf pH to deter fungal growth.
Always test fungicides on a small area first to ensure the plant tolerates the treatment without damage. Remove any severely infected leaves before spraying chemical controls. Combine these treatments with proper cultural care for the best results in combatting powdery mildew. With prompt action at the first signs of infection, you can keep your autumn sage healthy and maintain its seasonal display of colorful blooms.
HOW DOES POWDERY MILDEW SPREAD?
Mildew spores are spread by the wind in warm, dry weather, but don’t spread well when conditions are rainy and cool. Powdery mildew strains are specialized to certain groups of plants and generally don’t spread to other plant families. Spores can survive over winter in leaf piles and on plants, so it’s important to discard and not compost any plant debris dropped from infected plants to prevent spreading or allow it to resurface the following spring.
Essentially, there aren’t any plants that are completely immune to some form of powdery mildew, including vegetables, roses, trees and shrubs.
There are some plants that are more susceptible to powdery mildew than others, such as:
- Begonias
- Sunflowers
- Chrysanthemums
- Dahlias
- Roses
- Zinnias
- Melons
- Zucchini
- Squash
- Lettuce
- Cucumbers
- Potatoes
- Parsley
- Pumpkins
- Grapes
- Peppers
- Tomatoes
If you have recurring problems with powdery mildew, look for varieties that are noted to have improved disease resistance — this should be noted on the plant tag.
How to treat powdery mildew on roses? Remove and discard any affected leaves, as well as any that have dropped to the ground, and treat the rest of the plant preventatively. If you see powdery mildew on buds, clip and discard them as well. Thoroughly clean and disinfect any cutting tools that were used in the process. Apply one of the treatments above, such as a fungicide, baking soda, potassium bicarbonate or milk mixture once a week for 3 to 4 weeks and wait to see the results. Prevent further outbreaks with regular applications every couple of weeks or follow directions on product labels. Ultimately, results will be much better if the infection is caught at the first signs and treated quickly.
Try these roses that boast increased resistance to powdery mildew:
What is the best treatment for powdery mildew on squash? The milk mixture mentioned above seems to have better results that the other methods. Again, the science behind why it works is still being discovered, but it does appear to not only prevent a powdery mildew infection, but also boost the plant’s immunity.
Prevent & Treat Powdery Mildew and 4 Home Remedies that Work!!
FAQ
What kills powdery mildew fast?
Can I save my plant from powdery mildew?
Is Dawn dish soap good for powdery mildew?
How do you remediate powdery mildew?
How do I prevent powdery mildew on garden sage?
Prevention of disease is always the best first step. Ensure that sage is planted in a full sun situation with good soil drainage and excellent air circulation. In the case of powdery mildew on garden sage, good air circulation must be continually monitored.
Does Sage have powdery mildew?
In the case of powdery mildew on garden sage, good air circulation must be continually monitored. Poor pruning habits can lead to dense foliage which is a problem: instead of taking the tips of many the branches for culinary use, take a few branches entirely.
How do you prevent powdery mildew?
The best way to take care of powdery mildew is by prevention. Be sure to start with healthy plants. One powdery mildew homemade prevention tactic is to simply prune back any dead plant material during the normal pruning time. Do not plant things too close together in order to allow ample air circulation around the plants.
How do you get rid of powdery mildew on trees?
Avoid over-fertilizing plants and keep all suckers trimmed off of trees, since an overabundance of new soft growth makes them especially vulnerable to disease. A fresh mulch applied around plants in the spring may help to keep powdery mildew in soil from reaching the plants’ leaves.