Do you wonder why your plant has a white streak? This fungal disease causes low quality and quantity flowers and fruit in gardens, and infects a wide range of plants.
That white chalky stuff on your plants is not talcum powder or flour. It is powdery mildew, a fungus that spreads easily.
POWDERY MILDEW – What is it?
Plants of all kinds are affected by powdery mildew, a fungal disease. powdery mildew can affect a wide range of plants, depending on what species they belong to. There are many plants in a garden that are commonly affected, including cucurbits (squash, pumpkins, cucumbers, melons), nightshades (tomatoes, eggplant, peppers), and legumes.
Once the fungus has taken over a plant, a layer of mildew made up of many spores appears on its leaves. Powdery mildew is a fungal infection carried by the wind that slows down the growth of plants and, if severe enough, affects fruit yield and quality.
Powdery Mildew on Houseplants
A fungal disease, powdery mildew occurs on houseplants. The disease appears initially as powdery white fungus on the leaves of plants. As it spreads, plants can be infected with the fluffy white fungus throughout the entire plant. Over time this will cause them to succumb and die. It is extremely contagious, and if not controlled, it can spread to the rest of the whole plant.
Powdery mildew may affect plants outside, however, it occurs more frequently indoors due to conditions. Indoor powdery mildew needs temperatures around 70 degrees F. (21 C.). It occurs when there are poor airflow and low light, and it thrives in drier conditions than outdoor powdery mildew.
The fluffy stuff on the plant parts comes from the mycelium, which is formed from the fungal spores. Powdery mildew spreads by spores that break off on trees or plants. Mildew control in the home is important due to its contagious, aggressive nature.
How does powdery mildew spread?
You may find powdery mildew spores drifting through your garden with the wind or in old vegetative matter or weeds nearby if you have had powdery mildew before.
Powdery mildew is generally found in warm, dry climates where the relative humidity is high (60-80°F / 15-27°C) for the growth to occur. It doesn’t spread as far in cooler, rainy areas, and it is also slowed down by temperatures over 90°F (32°C). Shade-loving plants are more likely to be affected than those in direct sun, too.
Identification
How to identify Powdery Mildew Damage
- Plants infected with powdery mildew seem to be coated with flour.
- The powdery mildew usually appears on leaves, stems, and sometimes fruit as white, circular spots.
- Powdery mildew usually covers the upper surfaces of the leaves, though it may also appear on the undersides.
- The leaves of young plants are most vulnerable to damage. The leaves turn yellow and appear to dry out.
- Leaves may be twisted, broken, or disfigured when exposed to the fungus.
- As powdery mildew spreads, it will cover most leaves or areas affected by powdery mildew.
- This disease usually appears late in the growing season, especially when it affects the leaves, buds, and growing tips.
PREVENTION AND CONTROL
POWDERY MILDEW: How to Prevent it
Preventive measures are the most effective method of control of powdery mildew, as with all pests and diseases.
- Pick plants that resist powdery mildew for your garden. There have been many mildew-resistant cucurbit varieties developed from leading seed suppliers, so you don’t have to go to the grocery store to buy them anymore.
- Sunnier areas are best, as powdery mildew is more likely to develop in shady spots.
- Increase air circulation around your plants by selectively pruning areas that are overcrowded; this will help to reduce relative humidity.
- By sprinkling water from above, spores are washed off leaves. However, keep in mind that wet foliage can often aggravate other diseases, so there’s little benefit to relying on it as a preventative measure.
What is the best way to control powdery mildew?
- Protect (preventative) fungicides can be sprayed on infected plants. Sulfur, lime-sulfur, neem oil, and potassium bicarbonate are effective ingredients in treating powdery mildew. It is most effective to take them before you get sick or when you first notice the signs of an infection.
- Spray your plants with a bicarbonate solution instead of chemical fungicides if you don’t want to use chemical fungicides:
- A one-teaspoon solution of baking soda with a quart of water and spray the solution onto plants thoroughly. Properly applied, the solution will only kill the fungi it comes in contact with.
- Consequently, you must focus on preventing disease spreading on other plants once the plants are heavily infected so that you can get rid of the disease. Throw away all of the diseased foliage, stems, and fruit or burn them to destroy them. Don’t compost any infected plant, as the disease will persist in the compost and will spread via the wind.
Is Powdery Mildew a Problem?
Do not mist plants. Prevent the foliage from getting wet when watering. The white substance rubs off easily with your fingers or a cloth. Air circulation can be improved by placing plants farther apart, or using a small fan.
One plant that displays symptoms of infection should be isolated to prevent the spread of fungus. Pinch off the affected areas and discard them. Plants commonly affected are:
Begonia
African violet
Kalanchoe
Ivy
Jade
All specimens of powdery mildew on houseplants should be treated with chemical control if cultivar control fails. Water the plants well from underneath the foliage, then spray on 1 tablespoon (5 mL.) baking soda, 1/2 teaspoon (3 mL.) liquid soap, and 1 gallon (4 L.) of water for powdery mildew treatment indoors.
It will also help if you mix in 1 tablespoon of horticultural oil to ensure the mixture adheres to the fungus. To control powdery mildew indoors, use this powdered mildew control in spray form on the foliage. An organic method that works well is a milk spray. Make sure the milk is organic and free of hormones. One part organic milk plus nine parts water should be sprayed onto all surfaces of the plant once per week. To prevent mold, keep the foliage ventilated while the spray dries.
Fungicides for Powdery Mildew on Houseplants
To stop the spread of powdery mildew in your house when all else fails, use a household fungicide. If you receive any preparation, you will be exposed to some level of toxicity, so read the label carefully and use as directed. Any fungicidal spray should be sprayed outside to prevent drift of the particles into your home.
You can also use neem oil as a fungicide on house plants to prevent powdery mildew.
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