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.
Powdery mildew is one of the most common and destructive fungal diseases affecting balsam plants. It appears as white or gray powdery spots on the leaves, stems and flowers of balsams. While not always fatal powdery mildew can significantly impact the health and appearance of these popular ornamental plants. Fortunately, with some persistence and the right treatment methods, you can eliminate powdery mildew and restore the beauty of your balsams.
What Causes Powdery Mildew on Balsams?
Powdery mildew on balsam plants is caused by various fungal species in the Erysiphaceae family. The most common culprits are Podosphaera xanthii and Erysiphe cichoracearum. These microscopic fungi thrive in warm, humid environments.
Spores are spread by wind, water, and insects. When conditions are right, the spores germinate and infect plants The fungi siphon nutrients from the plant cells and gradually cause yellowing, wilting, and defoliation. Powdery mildew thrives when temperatures are moderate, around 60-80°F, and humidity is high.
How to Identify Powdery Mildew on Balsam Plants
Pay close attention to your balsams to spot powdery mildew early before major damage occurs. Warning signs include:
- White or gray powdery spots appearing on leaves, especially the undersides
- Powdery coating spreading to stems, buds, and flowers
- Leaves turning yellow and withering
- Premature leaf drop
- Stunted growth
If allowed to progress, powdery mildew can kill young plants and cause unsightly damage to mature balsams. Routinely inspect under the leaves for the earliest signs of infection.
Effective Powdery Mildew Treatments for Balsams
While powdery mildew can be stubborn, there are several effective treatment options available. Consistent, thorough application is key to success.
Organic Fungicides
Organic fungicidal sprays can help control mild powdery mildew outbreaks on balsams. Good options include:
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Neem oil – Derived from the neem tree, this oil coats the plant and smothers fungal spores. Mix 1-2 tsp neem oil per gallon of water and spray every 1-2 weeks.
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Potassium bicarbonate – Also known as baking soda, it disrupts the growth of powdery mildew fungi. Mix 1-2 tbsp per gallon of water and apply weekly.
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Milk spray – The proteins in milk inhibit fungal enzymes. Mix 40% milk and 60% water and spray plants biweekly. Apply in the early morning for best results.
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Sulfur – Available as a dust or spray, sulfur is effective against powdery mildew. Follow label instructions carefully, as too much can burn plants.
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Bacillus subtilis – This beneficial bacterium fights fungal diseases. Look for commercial products containing this active ingredient.
Chemical Fungicides
For moderate or severe powdery mildew, chemical fungicides are stronger and longer-lasting options. They should provide relief within 7-14 days. These are most effective if applied preventatively before infection takes hold. Options include:
- Myclobutanil
- Propiconazole
- Triforine
- Chlorothalonil
Follow label directions carefully when using chemical fungicides. Avoid spraying right before rain or when pollinators are active.
Bicarbonate Sprays
Baking soda (sodium bicarbonate) solutions can help prevent powdery mildew on balsams when sprayed weekly as a foliar spray. Baking soda raises the pH on leaf surfaces, creating an unfavorable environment for fungal spores to germinate.
Mix 1 tablespoon baking soda and 1⁄2 teaspoon liquid soap or horticultural oil in 1 gallon of water. Spray liberally over all plant surfaces, especially the undersides of leaves. This weak solution will not harm balsams. Repeat applications after rainfall.
Maintain Proper Growing Conditions
Choose balsam varieties labeled as powdery mildew resistant when possible. Also focus on growing healthy, strong plants that can better resist infections.
- Grow balsams in full sun to reduce humidity around the plants
- Space plants out for ample airflow
- Avoid overhead watering and allow soil to dry between waterings
- Promptly remove and destroy severely infected plants and fallen leaves
- Clean up and dispose of all crop debris after harvest
Strong air circulation, proper sunlight, and low humidity make it much harder for powdery mildew to get established.
How to Successfully Prevent Powdery Mildew on Balsams
Prevention is always the best solution when it comes to plant diseases. Here are some key tips to help avoid powdery mildew on your balsams:
Select Resistant Varieties
Look for balsam cultivars described as PM, powdery mildew, or disease resistant when shopping for plants or seeds. These varieties have been bred to better withstand common pathogens. Plant breeders are continuously working to develop improved disease resistance in balsams and other ornamentals.
Avoid Overcrowding
Powdery mildews thrive when humidity and foliage moisture are high. Overcrowded gardens set the stage for fungal issues. Space balsam plants 1-2 feet apart and prune or thin plants to improve air circulation. Leave ample room between plants and avoid planting in dense shade.
Monitor Soil Moisture
Overwatering raises humidity levels around plants. Allow the soil to partially dry out between waterings. Use drip irrigation or soaker hoses rather than overhead sprinklers. Water early in the day so foliage dries quickly.
Scout for Early Symptoms
Inspect plants frequently and remove any leaves or stems at the first sign of white fungal growth. This helps limit the spread of spores. Be on alert during warm, humid conditions favorable for powdery mildews.
Apply Preventative Sprays
Use organic fungicides like neem oil, potassium bicarbonate, or Bacillus subtilis as a preventative spray even before disease appears. Treat plants every 1-2 weeks during periods of high disease risk. Fungicide sprays help shield plants against initial fungal infections.
Sterilize Tools and Garden Debris
The fungal spores that cause powdery mildew can linger on used garden tools and leftover plant debris. Disinfect shears and other tools between plants with rubbing alcohol. Remove and dispose of heavily diseased foliage. Eliminating spore sources helps break disease cycles in the garden.
How Long Does it Take to Get Rid of Powdery Mildew on Balsams?
With consistent treatment, you should see gradual improvements within 7-14 days. The powdery white coating will begin disappearing from leaves and stems during this time.
Continue to treat plants for at least 2-3 weeks after the last visible sign of infection. This helps destroy any lingering spores and ensures the disease is eliminated. Resistant spores can persist in plant buds and crevices, so persistence is key.
You may need to prune out badly infected tissue to help speed recovery. Always sterilize pruners between cuts with alcohol. Remove and destroy all clippings to prevent spreading spores. Avoid composting infected plant debris.
When to Seek Professional Help
For gardeners struggling with repeated or severe powdery mildew infections, seeking professional advice may be warranted. You can contact your local county extension office to have a sample diagnosed and get personalized control suggestions for your environment.
In some cases, resistant strains of the fungus may have developed, rendering organic treatments ineffective. A lawn care company can help determine if prescription-strength fungicides are needed to resolve the issue. This is more common in agricultural settings than home gardens.
Preventing powdery mildew from establishing itself in the first place is more effective than trying to eradicate severe infections once they’ve spread. So focus on cultural practices that create poor conditions for fungal growth on your balsams. With some persistence and care, you can enjoy healthy, vigorous plants free of unsightly white powdery coatings.
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
How to treat powdery mildew on bee balm plants?
What kills powdery mildew fast?
Can you save a plant from powdery mildew?
Should I prune bee balm with powdery mildew?
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.
What fungi cause powdery mildew?
According to researchers, there are around 900 fungi species that cause signs of powdery mildew. The most common is Erysiphe cichoracearum. However, all plant mildews result in the same symptoms—a grayish-white fuzz on plant leaf surfaces. Powdery mildew affects ornamental houseplants, greenhouse crops, and garden flowers.
Can powdery mildew be cured?
As for powdery mildew treatment, there’s actually no method for affected foliage, which sadly cannot be “cured.” However, you can prevent the spores from traveling to other leaves on the same plant or nearby plants by cutting out the affected leaves and spraying the others regularly with a fungicide.
Can powdery mildew spread to other plants?
Left unchecked, powdery mildew spores can spread to other plants [ 1 ]. The infection will weaken the plant as it spreads. The plant leaves may also curl up, twist, or dry out. This fungal disease can affect fruit trees, vegetable crops, and other plants in your garden. Here’s how to get rid of powdery mildew naturally: 1. Vinegar