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8 Causes of Brown Spots on African Violet Leaves (With Fixes)

African violets are eye-catching houseplants with lush, velvety green foliage and drop-dead gorgeous blooms.

As pleasant as African violets are, they are prone to various problems that mar their beauty with brown spots. What could go wrong?

Brown spots on African violet leaves are commonly caused by diseases such as fungal leaf spots, bacterial blight, powdery mildew, ringspot, or rust. Isolate your plant and remove any affected foliage before beginning treatment. Also, insects, too much fertilizer, and watering issues can cause leaf scorch and low humidity. 

[1] African Violet Leaf Scorch

Exposure to hot, excessively bright sunlight is the primary cause of leaf scorch on African violet leaves. Common enablers or facilitators include:

  • Heat drafts
  • Extremely low humidity
  • Fertilizer burn
  • Soil compaction
  • Bacterial leaf scorch
  • Severe nutrient deficiency
  • Chemical or softened water injury
  • Poor potting medium
  • Your plant’s roots may have become overly crowded, and there isn’t enough room for root growth. It’s also easy for the soil to dry out, which leads to scorched and dried-out leaves.
Leaf Scorch due to Direct Sun Exposure
Leaf Scorch due to Direct Sun Exposure

Symptoms

If your African violet leaves are dry and crunchy with brown spots, you may have leaf scorch. It looks like a plant that has been over-exposed to the sun. In addition, leaves may turn yellow.

While various causes can lead to brown spots on the leaves, leaf scorch is a symptom of excessive sunlight exposure.

In addition, you may notice that the plant’s tips and edges have dried out and turned a drab brown hue. Finally, it’s not unusual for the leaves to be stunted in growth.

Treatment and Prevention of African Violet Leaf Scorch 

  • The scorched parts of the foliage will never turn green again. If it is due to bacterial leaf scorch, I recommend removing the severely scorched leaves and properly discarding them; if it is expected to be bacterial leaf scorch, I recommend coating wounds from cuts with cinnamon or shellac.
  • Relocate your African violet from a sunny location to a location with plenty of bright but indirect sunlight.
  • After a few days, your plant will recover if you give it plenty of water.
  • Apply some mulching material to the growing medium’s surface to keep moisture.
  • To combat leaf scorch, feed your African violet a diluted water-soluble fertilizer.

[2] Rusts on African Violet Leaves

A fungus causes rust on African violet leaves, which can be identified by the circular or oval bumps that appear on the plant’s leaves.

A fingertip is needed to get the spores out of the spots filled with spores. It usually thrives in moist environments with poor air circulation.

However, a combination of high humidity levels and wet leaves during watering can encourage the growth of rust.

Symptoms

Infected African violets typically display spore masses that can range in color from red to purple to brown to brownish-yellow to orange.

Leaves with these spots have a rusty appearance. They can appear as tiny, raised dots or specks on your African violet’s stems or foliage.

This condition will worsen and turn into pustule-like bumps if left untreated.

Eventually, the brown pustules will burst open, releasing the fungus spores that will be carried by water or wind to other leaves and turn brown.

It is only a matter of time before they infect healthy foliage and turn all of its leaves into brown spots.

Rust doesn’t usually kill your African violet, but it can hurt its health and growth.

You may notice a slow decline in development, the appearance of smaller leaves, and the death of stems.

In addition, leaves that have been severely damaged may turn yellow, dry out, and drop off too soon.

Treatment and Prevention of Rusts on African Violet Leaves

It’s best to avoid dealing with rust fungi entirely by following these simple precautions: 

  • Overwatering your African violet will encourage the growth of rust fungus, which thrives in moist environments.
  • Ascertain that new plants are disease-free and healthy. More importantly, select African violet cultivars resistant to rust and other diseases.
  • Overhead irrigation should be avoided. To avoid water splashing on the leaves, use drip irrigation or a soaker hose.
  • Water your African violet early in the morning to allow the leaves to dry completely.
  • As fungus spores overwinter in fallen plant debris, remove and discard it.
  • Ensure your African violet has plenty of air circulation both inside and outside the foliage. This helps to dry out the leaves. Consider spacing out your plants or using a fan to improve air circulation.

If your African already has some rust, here are some treatment options you have:

  • Remove and destroy affected foliage at first sight of rusty brown color. Make sure to disinfect the cutting tools after each cut with bleach solution.
  • Collect and destroy any fallen plant matter. Don’t compost them.
  • Treat your African violet with a houseplant-friendly fungicide like sulfur dust, Neem oil (Amazon link), or a copper/sulfur-based fungicide.

[3] Powdery Mildew

The Oidium fungus often causes powdery mildew in African violets. 

The white, powdery patches are typically densely packed with fungal spores and strands, which can appear as brown streaks or specks. 

The spores are typically carried or blown by the wind to other blooms and foliage on the same or different African violet plant.

Powdery mildew on African violet thrives under certain conditions, including:

  • Too much wetness on blossoms or leaves
  • High levels of humidity
  • Low light conditions combined with cool nights and warm days
  • Poor air circulation around the plant itself or between the foliage.

Symptoms

Powdery mildew can appear as a fine white or gray substance anywhere on the plant above the soil level.

In severe cases, your African violet stems, leaves, and flowers may become bleached or yellowed, and new growth may be stunted.

This is because mildew depletes nutrients and inhibits photosynthesis, resulting in browning or yellowing of leaf tissue.

Flowers, buds, foliage, and affected stems may wilt, turn brown, and die. The fungal infection usually affects African violets submerged, malnourished, or under-fertilized.

Treatment and Prevention of Powdery Mildew on African Violets

  • Get rid of severely infected parts that harbor the fungal spores. Wipe down the plant with a soapy solution to remove the powder.
  • Apply fungicide following the manufacturer’s instructions. You can use an organic option like Neem oil or try chemical fungicides. Apply every 7-10 days until the powdery mildew has been eliminated
  • Maintain good gardening hygiene, discarding any fallen plant matter.
  • Position your plant in a brightly-lit spot away from direct sunlight or overly damp conditions to facilitate hitch-free recovery
  • Isolate an affected plant from other houseplants until it is fully recovered

[4] African Violet Bacterial Leaf Blight

The bacterium Erwinia chrysanthemi causes bacterial leaf blight in African violets. Water, humans, or pests like spider mites can spread the bacteria.

Stomata (leaf pores) can allow bacteria to enter, but their preferred method of entry is through wounds on the foliage.

The pathogens thrive in warm, humid conditions, especially when there is a lack of air movement.

Excess moisture on blossoms, buds, or leaves can aid in the spread of bacterial blight infections. The disease can kill your African violet if it isn’t treated in time.

Symptoms

Soft, water-soaked lesions on the foliage of African violets are the most common sign of bacterial blight on that plant.

Depending on the amount of ooze and decay present, they can be a dark reddish-brown to black color.

Additionally, they impact the plant’s crown stems and roots, as well. You’ll find greasy or sticky threads inside the affected foliage if you cut it open.

Other symptoms of bacterial blight include:

  • Stunted plant growth
  • Foliage develops holes in areas where bacterial blight did the damage.
  • Paling of leaves; some may appear grayish, yellow, or brown.
  • The leaf grows brown spots, especially on the undersides.

Treatment and Prevention of Bacterial Blight on African Violets

A full-blown bacterial blight infection is almost always incurable and irreversible. Therefore, the best policy is to avoid problems in the first place.

  • Use a sterilized growing medium and a disinfected pot when potting or repotting your African violets.
  • Always wash and disinfect your hands before handling plants.
  • Avoid watering your plant from above or splashing the leaves. I strongly advise you to use a self-watering pot.
  • Avoid using too much fertilizer.
  • Avoid abrupt and extreme temperature changes.

For treatment, take the following steps:

  1. To begin, isolate your infected violet.
  2. Using a pair of sharp, sterilized pruning scissors, remove all infected and dead leaves.
  3. After each cut, disinfect the cutting instrument with a bleach solution of nine parts water to one part bleach.

[5] African Violet Foliar Nematode

It’s caused by tiny worm-like microorganisms that feed on the tissue inside your African violet.

These nematodes feed on the cells and lay eggs inside the foliage, resulting in browning leaves. Because these organisms are too small to be seen with the naked eye, you’re unlikely to see them.

African violet pathogens usually enter the leaves through the pores or wounds left by pest damage, cuts, or other damage. Foliar nematodes are almost always fatal to your plant if they are not treated promptly.

Symptoms

There are no apparent symptoms of foliar nematode infection in the early stages. However, your African violet is already infected when you realize what’s happening.

The most obvious sign is the appearance of sparkly brown spots on the undersides of leaf blades. Between the leaf veins, they often have a reddish ring.

Foliage undersides become speckled with tiny, hollow tan dots. As they grow, they lose their luster and become brittle. African violet foliar nematode symptoms include:

Other common symptoms of foliar nematode on African violet are:

  • Stems may become swollen.
  • Wilting leaves take a translucent brown appearance and feel soft to the touch.
  • Leaves may become pale, dull yellow, or grayish.
  • Foliage may develop yellow spots.
  • Brown, shiny spots on the foliage
  • Stunted plant growth

Treatment and Prevention of Foliar Nematode

Once the Foliar Nematode has infected your plant, it cannot be treated. So you’ll have to go to extremes to avoid it:

  • Disinfect the containers and use a sterilized growing medium when repotting your plant.
  • Before handling your African violet, thoroughly clean your hands.
  • When watering your plant, avoid splashing the leaves.
  • Isolate sick and new plants until you are sure they are disease-free.

[6] Ring Spot

Ringspot, also known as water spots, is caused by a sudden drop in leaf temperature.

It significantly reduces photosynthesis and causes irreversible damage to the palisade cells of the leaves. Irrigation from above with cold water is the most common cause.

The same thing can happen if you splash cold water on the foliage.

Light brown ring spots can form if the leaf temperature drops from 95°F (35°C) to 77°F (25°C) suddenly.

The rings may merge to form odd-looking brown spots on the leaves.

There is no way to undo the permanent ring spots caused by temperature differences, regardless of how long they are exposed.

The ringing spots are more tolerable in some African violet cultivars than others.

Symptoms

The distinguishing symptoms are the development of white to brown ring spots, arcs, streaks, or lines on the leaves. In addition, there is a chance that they will merge to form odd-shaped patches.

Treatment and Prevention of Ring Spot

When it comes to sudden temperature changes, African violets are extremely sensitive. Ring spots, on the other hand, cannot be removed.

Therefore, to encourage your plant to produce new leaves free of ring spots, you should correct the situation and implement proper cultural controls. To do so here is how:

  • Use room temperature water when watering your African violet
  • Irrigate your African violet from below
  • Avoid splashing cold water on the foliage.
  • Grow cultivars that are less sensitive to temperature drops

[7] Pest Infestation

Brown spots on your African violet leaves could result from a pest infestation.

They can be caused by direct tissue damage or by secondary infections caused by opportunistic pathogens.

Mealybugs: African violets are susceptible to a few mealybug species. The citrus mealybug and the Comstock mealybug are two examples.

They have a spongy body and are about a quarter of an inch long. They appear to be cottony because of a waxy white coating.

Symptoms

Keep an eye out for a cottony-like substance in the crevices and on the stems and leaves of the plant.

Sugary excrement excreted by the bees attracts ants and causes black sooty mold to grow. Then, they distort, stunt, and yellow the leaves as they eat the foliage.

Prevention and Control of Mealybugs

  • Inspect new houseplants for pests. Don’t forget to look for mealybug eggs at the bottom of the container.
  • Light infestations can be removed with rubbing alcohol-soaked cotton swabs. Repeat the treatment until the mealybugs are gone.
  • Consider using non-toxic insecticides such as pyrethrins, insecticidal soap, or Neem oil for mild to moderate infestations.
  • Neem oil and insecticidal soap should be adequate for severe mealybug infestations.
  • To control mealybug eggs and larvae, apply imidacloprid-containing insecticide granules to the soil (check the latest Amazon price here).

Cyclamen Mites

These bugs are not actual insects but rather spider relatives. However, they are the most common and serious pests of African violets.

They’re so small that you won’t be able to see them with your own eyes.

Low light, highly humid conditions (humidity levels of around 80-90%), and cool temperatures of around 60°F (15°C) are ideal for mites.

Symptoms

Cyclamen mites prefer to feed on the tender new growth in the crown’s center.

Hairy leaves that appear gray and stunted central leaves are among the most common symptoms.

Heavy infestations of flower and leaf bugs frequently result in the death of these insects. Sometimes, flower buds don’t open.

Prevention and Control of Cyclamen Mites

  • Space out your plants to prevent the spread of Cyclamen mites
  • Heavily infested African violets should be destroyed.
  • For plants that can be rescued, use a miticide spray labeled for African violets.
  • Consider using mite control spray (Check the latest price on Amazon here). 

[8] Fertilizer Overdose

Excess fertilizer salts in the soil may be blamed if your African violet has brown leaf tips and edges. 

A high salt concentration in the medium damages the roots and can also cause leaf “burn,” which appears as brown spots on the leaves.

Where the container’s rim meets the foliage, brown lesions may appear. The same is true for stems, which have brown streaks where they rest on the container.

Prevention and Control of Fertilizer Overdose

  • Remove any crusty scabs of fertilizer salts on the growing medium’s surface.
  • Deeply water your plant to flush out the excess fertilizer salts. Allow the liquid to percolate through the soil for about fifteen minutes. Repeat until all excess salts have been removed.
  • Repot your African violet in a fresh batch of well-drained potting mix labeled for the plant.

African violet leaves can develop brown spots due to natural aging and adverse environmental conditions such as low humidity.

This article will show you how to deal with specific problems and put the fixes into action.