Fungus Black Spots on Succulent Leaves: 6 Causes and Treatment

Discovering fungus black spots on succulent leaves can be a real downer, especially since they affect the most beautiful parts of these plants.

 Those juicy leaves are what make succulents great, but fungus spots can be a real buzzkill
Those juicy leaves are what make succulents great, but fungus spots can be a real buzzkill

It’s one of the most common challenges when caring for succulents, and the spots can manifest in various shades like brown, grayish, or yellow.

In this post, I’ll walk you through everything I’ve learned about dealing with fungus black spots on succulent leaves and share my approach to treating them.

1. Sooty Mold

Culprit 1: Spooty Mold, mainly caused by pests such as scales and aphids. Easily treatable with alcohol rubbing
Culprit 1: Spooty Mold, mainly caused by pests such as scales and aphids. Easily treatable with alcohol rubbing

Black smudges? Not dirt, but sooty mold, a fungal opportunist thriving on a feast laid by mealybugs, aphids, and scale.

These sap-sucking insects leave behind a sugary treasure trove called honeydew – a delectable buffet for the mold, but bad news for your succulent.

While sooty mold doesn’t directly harm your plant, it’s a shadow cast by the real culprits.

It blocks vital sunlight, stunting growth and weakening your succulent’s defenses.

At least, sooty mold is not a dead sentence to your succulent.

Treatment 

To address Sooty Mold, focus on eliminating the pests.

Start by wielding the power of insecticidal soap – a soapy bath that sends shivers down the spines of those sweet-toothed pests.

Once banished, gently wipe away the sooty mold with water or a mild soap solution, restoring your succulent’s vibrant skin.

Neem oil spray or rubbing with alcohol can also swiftly discard the pests for you.

2. Grey Mold 

Culprit 2 - Gray Mold: often manifests in high humidity areas with poor air circulation
Culprit 2 – Gray Mold: often manifests in high humidity areas with poor air circulation

Grey Mold is also known as Botrytis Cinerea. Its early signs involves tiny, circular spots of grayish-brown appearing on leaves and stems.

These seemingly harmless marks are the first whispers of trouble, soon erupting into a chilling sight: a fuzzy, gray mold that blankets healthy tissue.

This tenacious fungus thrives in environments with poor air circulation and high humidity.

It readily exploits wounds, decaying leaves, or even dead insects as its launchpad for invasion.

Once it starts manifesting, Grey Mold throws a million tiny confetti parties, flinging invisible spores everywhere!

These little party favors are sneaky seeds, waiting to sprout on any unsuspecting plant they bump into.

Think of them like dandelion fluff, but way creepier and for plants, not wishes.

Treatment

Relocate your succulent to a location with improved air circulation and apply a diluted dish soap solution to the affected areas
Relocate your succulent to a location with improved air circulation and apply a diluted dish soap solution to the affected areas
  • A homemade fungicide with Dishwashing Soap suffices. But you’ll need to ensure that the soap does not contain greasers or bleach.
  • Enhance air circulation for indoor plants by employing a compact clip-on fan.
  • Cut affected areas to prevent further spread.
  • Avoid top watering to minimize moisture and inhibit fungal growth.

Remember, prevention is the best cure! Grey Mold’s millions of airborne spores seek cracks and dampness, turning vibrant greens to fuzzy grays.

Pamper your succulents with sunshine and air, and they’ll shrug off those moldy advances.

3. Fusarium Wilt 

Culprit 3 - Fusarium Wilt appears with black spots on the leaves that will dry out and turn yellow
Culprit 3 – Fusarium Wilt appears with black spots on the leaves that will dry out and turn yellow

Fusarium wilt, a soil-borne fungus, isn’t a picky eater. It feasts on a variety of plants, leaving trails of wilted leaves, yellowing foliage, and stunted growth in its wake.

But for our fleshy-leaved succulents, it weaves a particularly sinister story.

Picture this: your once plump and perky succulent begins to deflate like a punctured balloon.

The leaves, proud jewels of green, seem to melt from within, marred by sinister black scars that spread like ink blotches.

Unlike other plants where leaves fall, the succulent battles the wilt internally, trapped in its own withering shell.

Why the panic? Because against this fungal fiend, we’re weaponless.

Fusarium wilt has no known cure, and it clings stubbornly to the soil, a persistent plague with an infectious glint in its eye.

It’s a relentless predator, draining your succulent’s life and eyeing your entire garden as its next feast.

While Fusarium Wilt has no cure for succulents, removing the infected plant at first sign can protect others
While Fusarium Wilt has no cure for succulents, removing the infected plant at first sign can protect others

Symptoms

  • Wilting leaves: They droop and wrinkle, looking like deflated balloons.
  • Black discoloration: Dark spots or streaks appear on leaves and stems.
  • Yellowing: Green fades to yellow along with the wilting and blackening.
  • Stunted growth: Your succulent stops growing or grows much slower than usual.

No Treatment

Don’t just throw your ailing succulent away. You have more tasks ahead to truly protect your garden against Fusarium Wilt.

Dig out the infected succulent, severing its connection to the soil, and banish it with fire or scalding water – leave no trace for the fungus to resurrect its villainous plot.

Remember, speed is your ally. This silent stalker travels fast, and delaying action could doom your entire garden.

Additionally, sanitize your tools and the affected soil. Don’t reuse them to prevent the spread of the fungus.

4. Anthracnose

Culprit 4 - Anthracnose: it is also highly contagious but curable if you act fast
Culprit 4 – Anthracnose: it is also highly contagious but curable if you act fast

At first, you might notice subtle pale circles on the plant’s skin, hinting at a potential problem.

These small spots grow into sunken areas, showing that the fungus is taking over.

As the infection gets worse, lively plant parts dry up, turning into brittle remains, reminding us of life lost.

Anthracnose uses tricky tactics, making leaves look yellow or wilted, pretending to be common issues to hide its harmful plans.

When attacking succulents, it makes the leaves feeble and easy to fall off even with the slightest touch.

Symptoms

Anthracnose infection typically manifests as circular, pale, sunken, or brownish spots, resulting in the desiccation of plant tissues and the adoption of a rigid, bark-like texture.

Isolate your succulent and treat it with either benzopyrazole or mancozeb spray according to the package instructions
Isolate your succulent and treat it with either benzopyrazole or mancozeb spray according to the package instructions

Treatment (Make it Urgent!)

  • Quarantine: Separate the infected succulent from others and place it in airy location without direct sunlight.
  • Spray: with benzopyrazole or mancozeb every 2-3 days for two weeks or more. Don’t forget to follow package instructions closely.
  • Keep the rest of your succulents in well-ventilated locations.
  • Pay close attention to other succulents you are having in the meantime as well. Some may have already been infected too.

5. Rust Spots

Culprit 5 - Rust Spots: True to their name, the spots resemble rust on metal
Culprit 5 – Rust Spots: True to their name, the spots resemble rust on metal

If circular spots on your succulent appear orange, yellow, or reddish resembling rust, suspect the presence of Rust Fungi.

While not fatal, affected plants may exhibit stunted growth, discoloration, and weakness.

If heavily impacted for consecutive years, untreated cases can lead to plant death. Excessive rust spots can also hinder photosynthesis.

Treatment

  • Quarantine: Isolate affected plants to prevent windborne spread.
  • Wash with Water: Take the infected succulents out of their original planter, cleanse the leaves, stems, and roots with clean water, and trim any excessive hair roots using scissors. 
  • Boil or Burn: the affected succulent’s soil and removed parts.
  • Spray: Apply mancozeb twice a week for 2-3 weeks. You can also opt for copper spray or sulfur powder to tackle the fungi.
  • Replanting: Once the wound has healed, replant the succulent in new soil.
Isolate and treat the plant with copper spray or sulfur powder
Isolate and treat the plant with copper spray or sulfur powder

6. Phytophthora 

Phytophthora, a root rot disease, induces large black, wilted spots on succulent leaves.

To confirm the disease, inspect the root systems for brown and dead tips. Affected succulents eventually yellow and succumb to the infection.

No Treatment

Unfortunately, Phytophthora is a lethal disease with no known cure.

The best course of action is to eliminate it from the garden.

Remove debris and old, potentially contaminated medium, sanitize the area, and clean tools thoroughly.

Culprit 6 - Phytophthora: Also a fatal strike to your succulent and contagious
Culprit 6 – Phytophthora: Also a fatal strike to your succulent and contagious

Symptoms

  1. Wet Spots: It begins with wet spots on leaves, stems, fruits, or the base of the plant. These spots might get bigger, especially if it’s humid or rainy.
  2. Changing Colors: As the problem gets worse, the spots turn brown, grey, or black. This is different from the usual green of the plant.
  3. Rotting Parts: In later stages, the affected parts become soft and start to rot.
  4. Plant Decline: In serious cases, the plant starts to look sick. Leaves fall off, stems droop, and parts of the plant give in to the disease.

How to Know It’s Phytophthora:

  1. Spots type: On leaves, you might see spots near the veins or edges. Sometimes, these spots have rings, which is a sign of the disease.
  2. Stem Issues: Stems may have long, sunken spots, sometimes going all around, stopping the plant’s important life flow.
  3. Succulent leaves become mushy and lackluster, and their usual lively look is gone forever.
  4. Crown Quietness: Crown rot is often difficult to see but can lead to wilting, stunted growth, and eventually plant death.
Again, sanitize your garden thoroughly and apply prevention methods to stop it from creep up again
Again, sanitize your garden thoroughly and apply prevention methods to stop it from creep up again

Prevention

It’s unfortunate that you might have to part ways with your cherished succulent at this stage.

However, you can take steps from here on to keep the disease from sneaking back into your plants.

  • Avoid planting in low-lying or poorly drained areas. Opt for mounded, raised beds or container gardens to enhance drainage.
  • Replace susceptible crops with plants like peppers.
  • Opt for slow drip irrigation over overhead watering to minimize surface runoff.

Final Thoughts

Good Luck taking care of your succulents!
Good Luck taking care of your succulents!

When tackling the removal of highly infectious fungi, exercise utmost caution.

Thoroughly sanitize your tools and affected areas, and ensure proper disposal of the soil or affected parts.

Avoid casually tossing them on the ground; instead, promptly place them in tightly sealed bags or immediately treat with alcohol or boiling water.

As you navigate these challenges, remember: each action you take contributes to the resilience and vibrancy of your succulent haven.

Despite the setbacks, your garden’s future can indeed be bright, lush, and flourishing.

May your succulents thrive, bringing joy and beauty to your space for years to come!