How to Treat Black Spots on Aloe vera Plant (Causes and Prevention)


Black Spots on Indoor potted  Aloe vera Plant

For many years, people considered growing an aloe vera plant not mainly for its tropical design but also because of its medicinal capabilities.

While there are claims that this plant is capable of healing treatment, still it’s not immune to having various complications. The most common incident is your Aloe Vera having visible black spots on its leaf.

The best way to treat those black spots in your aloe vera is to know first what causes the infection. The typical process that you can consider right away is to regulate its water intake, provide adequate indirect sunlight, and proper termination of pathogens.

What Are the Black Spots on My Aloe Vera plant?

The black spots on your Aloe Vera usually referred to as Leaf Spot, are caused by a pathogen known as the Alternaria alternata.

This pathogen destroys your plant’s’ antimicrobial defense, which results in visible spots in your plant’s leaves. (Source: Science Direct)

Why Does My Aloe Vera Have Black Spots?

There are many possible reasons why your Aloe Vera is suddenly showing black spots on its leaves even though they’re healthy and growing days before. 

To give the proper treatment for your plant, you need to make sure first that you’re knowledgeable on what kind of cause you’re dealing with.

Sometimes, applying the wrong cure might put your Aloe Vera in a more complicated situation. 

With that, you may want to continue reading to know what are these causes that you need to watch out for.

Excess Light/Scorching

Though your Aloe Vera enjoys a sunnier environment, still excessive lighting can produce damage to its system. 

This scenario mostly happens when you relocate your plant from a place with a medium-light or shaded environment going to an area with direct sun exposure.

Another probable situation is when you’re using an artificial light located near your aloe plant.

The common symptoms are the appearance of brown to black spots in their leaves followed by blanching and wilting.

Treatments:

  1. Relocate your indoor aloe in a shaded area of your house just enough to receive indirect hits of sunlight. Significantly, limit your plant’s exposure from 4 to 6 hours a day to avoid sunburn.
  1. Ideally, a western facing window with a sheer curtain is the right spot for your plant to thrive.
  1. If you’re using artificial light, make sure to maintain a two-meter distance between the light and your plant.

Low Humidity

Most of the succulent, including your aloe, prefer a low humid environment, but despite that, too much exposure in a low humid area may produce unwanted spots on its leaves. 

Because there’s a lack of humidity, your plant is forced to pull water from its system, and without enough water, photosynthesis will be compromised.

Aside from the spots, your aloe might also suffer growth deterioration, which causes its leaves to wilt and eventually fall.

Treatments:

  1. Transfer your plant to a well humid location. But you need to bear in mind that too much humidity could invite pathogens to infest your aloe, making it more prone to diseases.
  1. Gently spray some water in its leaves to receive the proper moisture that it needs.
  1. You can use a humidifier to increase the humiding surrounding your aloe vera.

Watering Problems

It’s essential to know your plant’s natural environment since not all types of plants require the same amount of water.

Your aloe vera commonly grows in areas with a tropical climate, thus making it tolerant to drought. 

Your plant does not require too much water from time to time since it has an adequate water supply to stand high-temperature areas. 

Too much watering of your aloe can cause severe damage to its root system, making it incapable of transporting enough water and nutrients to the cells of those leaves.

As a result of water and nutrient inefficiency, black spots might suddenly appear.

Treatments:

  1. Proper watering is the best practice to save your aloe if you suspect that it suffers from overwatering. While there are many suggestions on when to water your plant, the best way is by touching if the soil is dry only then that you will irrigate your plant.
  1. If you found out that it’s soaked in a high volume of water, you need to halt watering for at least 15 days. In that way, you are allowing its roots to recover from stress.
  1. Allow a proper drainage system in your aloe by ensuring that it has enough holes underneath or by elevating it from the ground.
  1. If the damage caused by overwatering is severe, consider repotting your plant. If possible, use a new pot and a well-draining soil mixture to avoid bringing the pathogens lurking in your old pot. Also, don’t forget to remove infected roots and leaves.

Low Temperature

A low-temperature environment can create a hefty amount of moisture on your aloe’s soil, creating a higher chance of pathogen infestation on its root system.

Typically, your aloe loves to grow in an environment having a temperature level between 60-75 °F (16-24°C).

There are also cases wherein your plant might experience frost damage, especially during the winter seasons. Because of the low-temperature level, the stored moisture on your aloe leaves tends to freeze, causing damage to your plant’s tissue.

Treatments:

  1. Give your aloe the necessary insulation, especially during the cold season. Preferably, you can use blankets or cover to provide heat, negating the cold season’s impact.
  1. If in case your insolation is not enough, transfer your plant to a well-heated area. You can also use an artificial lighting system to aid its sunlight needs. Just remember to place the light 2 meters away from the plant.
  1. Remove the damaged leaves since they will rot in a couple of days and might infect the other remaining healthy leaves.
  1. Stop or lessen watering your aloe during cold seasons since they have enough moisture to survive for an extended period.

Fungal Diseases

The occurrence of fungal diseases is the major problem of your aloe vera, especially during winter. 

Fungi are commonly attracted to a moist environment. Therefore, undrained pot, wet soil mixture, and humid areas are the culprits’ usual habitat.

Check the table below to have a detailed list of possible fungal diseases and better understand how you can confirm these unwanted guests’ presence from your aloe vera. (Source: Plant Village)

DiseaseReasonsSymptoms


Aloe Rust
This disease is caused by Phakopsora Pachyrhizi, a fungus that travels through the wind. It destroys the outer leaf structure and produces spores, which destroy the leaves of your aloe. It usually thrives if there is excessive water or moisture on the leaves. Common symptoms are the occurrence of yellow spots on the leaf surface, which eventually turns black, orange spore masses underside the leaves, and the dropping of your plant.


Anthracnose
This disease’s main culprit is the Colletotrichum gloeosporioides, a common fungus that usually attacks ripe fruits. They enjoy warm and wet weather and can quickly propagate through water splash.Initially, in its early days, you will see a dark green oval on the leaves. Over time, the center of the lesions become brown until it forms a dark circular spot.


Basal Stem Rot
This infection is caused by mycotoxins produced on the soil of your plant by a group of fungi known as Fusarium. The emergence of these fungi happens in cold conditions.The early signs start with reddish-brown rotting on the base of your plant. The rotting will eventually move upward to the stem until it forms some dark spots on the leaves.


Leaf Spot Disease
This disease is the most common reason for the black spots in your aloe plant. It is caused by Alternaria alternata, a fungus capable of destroying your plant’s tissue and antimicrobial defenses. Alternaria will thrive in a place where moisture is abundant.The symptom starts with tiny dark brown spots, which enlarges through time until it fully decays the leaf of your aloe.

How to Treat Fungal Diseases

Aloe Rust

  • If you suspect that your aloe is suffering from Aloe Rust, immediately remove all excess water you can see on the pot dish.
  • Relocate your plant in a bright or high-temperature room to aid the soil with its draining process.
  • Stop watering your plant for a week or until the soil dries.
  • Provide proper spacing in between your plants to give appropriate ventilation.

Anthracnose

  • Remove infected parts to avoid spreading of the pathogens. Do not use those parts for compost purposes, instead immediately dispose of them in your garbage area.
  • Isolate your aloe and all other plants that have been infected with pathogens.
  • Apply liquid copper spray once a week, preferably during the morning.
  • You can also try to use Neem oil spray to make your treatment more organic. Use this once a week until the visible signs of Anthracnose are gone.

Basal Stem Rot

  • Apparently, this is a more severe case to handle if you are new in gardening since you need to check your plant’s roots. 
  • In checking, make sure to gently detach your aloe from the ground and inspect the roots. If you see mushy roots, then most probably your plant is suffering from this ailment.
  • Remove all the infected roots and dispose of them immediately. If there are still healthy roots left, then your aloe might probably survive, otherwise, dispose of the whole plant.
  • Wash the remaining healthy roots with clean water, then cut off all infected leaves and stems.
  • Now you need to consider repotting your aloe to avoid further damage. Effectively, do not use the same pot and soil mixture since there’s a high chance that it’s already contaminated.
  • You can spray fungicide on the roots of your aloe before planting it in its new home.

Leaf Spot Disease

  • When you find out that your aloe is suffering from a leaf spot, immediately isolate your aloe from other plants.
  • Place it in a low-humid environment to prevent a continuous build-up of moisture.
  • Carefully cut off the infected leaves to prevent the spreading of fungi to the remaining healthy parts.
  • Apply fungicide to your plant to make sure that you eliminated most of the invaders.
  • Stop watering your plant for a week or until the soil dries up. As much as possible, do not water the infected leaves of your aloe to stop the fungal propagation.
  • Lastly, clean up your area, don’t leave any infected parts in your garden. This might sound repetitive, but never use those infected parts for compost purposes.

Bacterial Diseases

Another vital factor that you need to check as well as a bacterial infestation. Though bacterias are less complicated and can easily be treated than fungi, we still can’t just shrug it off.

Without proper treatment, your aloe might be in real danger, even with its antimicrobial properties.

The most usual bacterial disease your aloe can get is Bacterial Soft Rot caused by Pectobacterium chrysanthemi, which penetrates your plant’s defensive enzyme, resulting in a structure breakdown.

Though it commonly targets root crops and vegetables, your aloe is still not vulnerable to its fatal invasion once your environment permits its existence.

The common visible signs are damp, dark spots in your aloe leaves, which enlarge and sink after a couple of days.

Your plant’s leaves might also be experiencing some wilting and dropping, specifically on the lower portion, not to mention the strong odor you can smell easily.

Treatments:

  1. As of today, there is no proven solution for Bacterial Soft Spot, especially if your aloe already received severe damage to its tissues. 
  1. If all the leaves are infected, immediately dispose of your plant to avoid spreading the bacteria.
  1. If there are still healthy leaves intact in your plant, you can try propagating it by cutting off some healthy leaves and placing them in water over time to grow roots. Some gardeners refrain from doing this for the simple reason that there’s a high chance that it will produce shriveled, unhealthy leaves.
  1. What you can try to do is use aloe pups or aloe offsprings in propagating your plant. In doing this, make sure that the pups are already big enough to be reproduced. Ideally, it should be one fourth to one fifth the size of its parent plant.
  1. Using a clean knife, cut off the pup away from its parent plant. Check if there’s a visible rooting system beneath the pup.
  1. Plant it in a small pot with a well-draining soil mixture. After seven days, you can start watering your young aloe every week.

Insect Infestation

If you think that your aloe plant is safe from insect attacks indoors, you better think again because most of the time.

This pest is the main culprit of why your aloe is having those black spots on its leaves.

Terminating different insects from your aloe needs different approaches. Therefore, you must have the proper knowledge in dealing with them. To help you know more about those pests, check on the table below.

InsectsAppearanceCausesSymptoms



Mealybugs
Oval-shaped with an unarmored wax-covered body. It does not have wings and often appears as a cottony substance on the leaves.This insect sucks sap from your plant’s phloem and excreting honeydew that reduces the quality of your plant structure.It will start from a small discoloration on your aloe’s leaves then turn into a dark brown spot, thus becoming darker if not treated.


Aloe Vera Aphid


Commonly appears in a pear-shaped light green color with antennas.
These pests infest on the base or the damaged end of your leaves. Like Mealybugs, they also discharge honeydew resulting in the development of molds.
Aside from dark spots due to lack of nutrients, your aloe also shows growth deterioration.


Aloe Mites

This microscopic creature has a worm-like appearance with two pairs of legs.
These mites love feeding with your plant’s chlorophyll, thus hindering the process of photosynthesis. They also inject cancerous chemicals that affect the growth of your aloe.A small yellowing of your plant’s leaves turns darker from time to time until it becomes a total dark spot.

How to Treat Insect Infestation

Mealybugs

  • If you encounter a mealybug invasion in your aloe plant, consider spraying a mixture of alcohol and dish soap. Just combine 3 to 5 drops of dish soap into a cup of alcohol.
  • Directly spray it on every part of your plant, not just on the visible areas where mealybugs reside, to assure total extermination. Do this once a week until the infestation stops.
  • You can also apply neem oil for an organic fungicide approach.
  • If the infestation is severe, use insecticidal soaps and sprays to save your aloe vera plant.
  • If the infestation persists, you need to dispose of your plant to avoid the mealybugs’ spread.

Aloe Vera Aphid

  • As much as possible, don’t use chemical products since aphids have lots of natural predators, including ladybugs and mantis, thus preventing massive infestation.
  • Gently rub the leaves using cotton soaked in alcohol.
  • Use insecticidal soaps once a week until the infestation stops.

Aloe Mites

  • Aloe mite is also one of the favorite foods of ladybugs and beetles, naturally, they will dispose of these pests.
  • If you suspect that mites are infesting your aloe, spray a mixture of alcohol and water directly into the leaves.
  • You may first isolate your aloe from the rest of your plants to avoid transferring mites.

Fertilizer Problems

Though it offers the necessary help for your aloe’s growth, this could lead to your plant’s vital situation when misused.

There are certain nutrients that your aloe needs, and you need to be aware of those before coming up with a solution for using fertilizer.

In case you want to serve your plant some extra nutrients, you can check the graph below for reference.

NutrientsProblemsSymptomsCorrections
PhosphorusA low level of soil pH affects the production of phosphorus.Leaves turned darker with reddish-purple spots.Add phosphate or greensand to your soil.

Magnesium
Insufficiency in Magnesium when soil pH is lowLeaf discoloration, especially on the lower part.Apply a mixture of 1 tbsp Epsom salt and 1 liter of water and use it as a soil drench.
NitrogenToo much water dilutes the presence of Nitrogen.Yellowing of leaves and minimal dark spotsAdd ammonium nitrate to the soil. Another option is using animal manure.
CalciumCalcium is most abundant in sandy soil and water thus, the problem occurs in excessive calcium limiting other nutrients.Distorted or irregular shape of leaves and sudden appearance of dark or brown spots.Stop using calcium and gypsum-based fertilizer and limit from watering your plant.

(Source: University of Arizona)

How to Prevent Black spots on Aloe vera Plant

Though it looks complicated because of the factors mentioned above, there are still ways to prevent your aloe from having those dark spots on its leaves.

  1. Make sure that your houseplants are clean to avoid possible pathogen infestation.
  1. Remember that your aloe loves to have enough sunlight, so make sure to provide it accordingly.
  1. Do not overwater your aloe. Always check the soil before watering to avoid unnecessary build-up of moisture. 
  1. Ensure proper drainage to avoid waterlogging. If possible, add enough holes on your pot to aid the draining process.
  1. Be knowledgeable in buying fertilizer, inspect first the needs of your plant before purchasing.

Final Words

Soothing sunburns, adding vitamins to your hair, and treating acne are some of the benefits of your aloe, the reason why most people love this plant in their home garden.

Though it’s easy to maintain, you still need to be responsible for sustaining its proper needs.

Otherwise, it will suffer from various causes, including the infestation of insects and pathogens that may lead to the sudden appearance of dark spots or, worst, to your plant’s demise.

If you found that your aloe has dark spots on its leaves, refer to the causes first before applying any remedy. Your plant doesn’t need too many fertilizers, so as much as possible, limit the usage of those.

As serious as it may seem, this kind of scenario could easily be prevented through proper knowledge and awareness in taking care of your plant.

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

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