African violet white leaves

African Violet Fungal Control: What Causes Powdery Mildew On African Violets

White powder on African violet leaves is an indication that your plant has been infested by a nasty fungal disease. Although powdery mildew on African violets isn’t usually deadly, it can definitely impact the overall health and appearance of leaves and stems, stunt plant growth and reduce blooming substantially. If left untreated, leaves may dry and turn yellow or brown. Wondering what to do about African violets with powdery mildew? Looking for tips on African violet fungal control? Read on.

Causes of Powdery Mildew on African Violets

Powdery mildew thrives where conditions are warm and humid and air circulation is poor. Temperature fluctuations and low light can also contribute to fungal disease. Treating African violets with powdery mildew means taking precautions to avoid these conditions.

African Violet Fungal Control

If your African violets have powdery mildew fungus, you must first isolate affected plants to prevent the spread of disease. Remove dead plant parts too.

Reduce humidity. Avoid overcrowding and provide adequate space around plants. Use a fan to circulate the air, especially when the air is damp or temperatures are high. Keep plants where temperatures are as consistent as possible. Ideally, temperatures shouldn’t vary more than 10 degrees.

Sulfur dust is sometimes effective, but usually doesn’t help much unless it’s applied before the mildew appears.

Water African violets carefully and avoid wetting the leaves. Remove blooms as soon as they fade.

If powdery mildew on African violets doesn’t improve, try spraying the plants lightly with a mixture of 1 teaspoon of baking soda in 1 quart of water. You can also spray the air around the plant with Lysol or another household disinfectant, but be careful not to get too much spray on the leaves.

You may need to dispose of badly affected plants that show no sign of improvement.

What is powdery mildew?

  • Powdery mildew is a fungus which grows superficially on a plants surface.
  • In case of African violet plants, this can be on the leaves, stems, buds or blooms.
  • Patches of powdery mildew can enlarge and in some cases cover a leaf both front and back and entire blooms.

Why do you have to remove powdery mildew from African Violet plants?

  • To maintain a healthy plant it is important to remove powdery mildew as soon as possible.
  • Powdery mildew is responsible for slowing the growth of the African Violet plants.
  • It can also cause the leaves to yellow, become dry and brown.
  • In extreme cases if powdery mildew is not controlled it can cause plant growth dormancy and make the plant appear extremely unsightly!!

Where can powdery mildew on African Violet plants be found?

  • Powdery mildew can be found on the outer surface of leaves, stems, buds and blooms.
  • Young new growth of leaves and blooms may be particularly susceptible.

What does powdery mildew on African Violet plants look like?

  • Powdery mildew looks like patches of white or powdery growth.
  • On leaves and blooms they can look like powdered sugar dusted on them or like white spots or a white substance sitting on them.

Why do African Violet plants develop powdery mildew?

  • In the case of African Violets, powdery mildew can develop due to high humidity (hot and humid conditions).
  • Overcrowding of plants in a tray can cause powdery mildew due to poor air circulation.
  • This can also lead to neighboring plants being infected too.
  • Condensation on leaves due to temperature fluctuations between day and night can also cause powdery mildew (cold and wet conditions).

How to remove powdery mildew from African Violet plants?

  • First remove all infected leaves, buds and blooms.
  • Also remove all the remaining healthy buds/bloom stalks too. Second, water the plants well.
  • For plants with a light coating of mildew or first signs of mildew, use a Q-tip dipped in 50% diluted solution of rubbing alcohol with water to gently wipe the mildew away.
  • Or you can also lightly spray the plant with a 50% solution of rubbing alcohol.
  • Make sure to treat the leaves underneath surfaces too.
  • Other treatments methods include (always use tepid water):
    1. One tbsp baking soda, half tsp liquid soap and One gallon of water.
    2. One: nine parts organic milk mixed with water.
    3. One capful of Lysol mixed with 500ml of water.
  • Remember not to spray very close up on the plant, spray in the air from a distance so the solution gently falls onto the plant.
  • If the natural methods are not effective, spray diluted organic neem oil or a commercial fungicide over the plant foliage.
  • Please follow exact directions on the container.

How to prevent African Violets from developing powdery mildew?

  • Ensure basic routine care of African Violets to prevent development of powdery mildew.
  • Routine grooming of the African Violet plant, i.e. removing dead, dried, yellow leaves and dried blooms can ensure that it maintains good growth.
  • For more information on routine grooming African Violets, you can visit my blog post, “How To Groom African Violet Plants?“.
  • Make sure the plant stands and surrounding areas are clean..i.e. the plant tray, tray lids, pots, tools and watering cans/containers are all clean and disinfected twice a year with a diluted bleach solution (1:9 bleach: water ratio).
  • Space plants out evenly to ensure good air circulation, do not over-crowd.
  • Purchase only disease free plants, inspect them well before purchasing.
  • During hot summers use a fan to promote air circulation.

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Powdery Mildew On African Violets – Knowledgebase Question

According to the African Violet Society of America, powdery mildew can be treated with several fungicides; you might want to refer to their trouble shooting chart for the specifics:
Also, be sure to read and follow the label instructions carefully. Air circulation and good sanitation are also very important in an effort to control mildew.
Most of the plants we grow are hybrids. However, in the wild, the plants would not be subjected to the stresses of a greenhouse and would be in a more ideal environment.
In a closed terrarium, where it is still and very humid, they do not seem to suffer disproportionately from fungal infections as long as the plants are healthy from the beginning. In the wild, if they grow beneath larger plants, rain might not hit them on a routine basis. In my experience with these as houseplants, a certain amount of tepid water on the leaves does not harm them as long as they are not in direct sunlight and as long as there is good air circulation to dry them off quickly.

My African Violet Leaves Turned White. What Can I Do?

There are a few factors that could be coming into play. The plants may be getting too much light, so you might want to first try moving the plants to the sides of your light table where the light is not as intense as in the center. If the light fixtures are adjustable, you can also try moving the lights farther away from the plants. Yellow or white foliage can also be caused by overly compacted soil or by room temperatures that are too high. If it’s the former, repot the plant in the same size pot, removing as much of the old soil as possible without damaging the root ball. Replace it with fresh soil.

If you have a tiered light setup or a light cart, moving the plants to the bottom level often helps, because temperatures are cooler. The other possible problem is that the plant may be getting insufficient nitrogen. In this case, try a fertilizer rich in nitrogen (that’s the first number listed in the three-digit analysis label on fertilizers). Usually, a well-balanced fertilizer for African violets is sufficient. Avoid purchasing fertilizers that contain urea, which hinders the violet’s ability to absorb nutrients and water. You may also know that cold water on African violet foliage can discolor it. Usually the affected area turns beige and corky rather than white. Water the plant from the base or use room-temperature water.

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