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Brown Spots on Aloe vera Plant (Causes and Solutions)

It’s uncommon for Aloe vera plants to look unhealthy because this tough plant rarely gets in trouble. It can withstand drastic changes in the environment such as long periods of drought.

But as the old lyrics say, “Even the best fall down sometimes”, your aloe vera will also have that moment of weakness. 

One problem you’ll encounter on your aloe plants is the brown spots that appear on their leaves.

These spots will come in different sizes and shapes. The color will vary from light brown to dark ones depending on what causes the problem. 

Brown spots on aloe vera are possibly caused by diseases (aloe vera leaf spot, aloe rust), edema, excess light, pest infestation, fertilizer problem, poor air circulation, high humidity, and frost damage. Most of the time, the factors mentioned are related to each other. That’s why the problem may arise as a result of the combination of such causes.


Indoor potted aloe vera

Why Does My Aloe vera Plant Have Brown Spots?

Brown spots in aloe vera can be explained by various phenomena. Some are due to biological reasons while others are due to physical and chemical factors in the environment. 

To help you understand each cause, we will explain the mechanism working behind every factor so keep reading:

Aloe Vera Leaf Spot Diseases

Alternaria alternata is the pathogen responsible for the leaf spot disease in aloe vera. This organism destroys the tissues of the leaves which in turn results in discoloration. The disease also reduces the plant’s antimicrobial capacity. 

The leaf spots would initially appear as small dark brown spots on the surface of the leaves. 

These spots enlarge through time until they join together and form huge damage. The color of the infected part becomes dark brown to black. 

Quick Solutions: 

There is no definite treatment for these diseases. However, there are ways to manage them so they will not bring too much harm to the plant. 

  1. Isolate your aloe. You should isolate any diseased plant from other plants to prevent the disease from spreading. 
  2. Place in a dry, less humid location. A moist environment is a favorable condition for fungi to thrive. Thus, disease emergence is high when the humidity is high. 
  3. Remove the infected portions. Cutting off the parts where the disease is present will help reduce the probability of spreading the pathogens. 
  4. Do not water the foliage. Watering the foliage will cause the leaves to be constantly wet. This becomes favorable for pathogens to grow to make your aloe plant more susceptible to diseases.  

Aloe Rust

Aloe rust is a fungal disease caused by the pathogen Phakopsora pachyrhizi. An aloe that is infected by this fungus will show small, yellow spots on the leaf surface. Later, those small spots grow larger and become brown in color.

Quick Solutions:

To manage a diseased aloe vera, please refer to the quick solutions mentioned above. 

Edema

If you notice that the surface of the aloe vera leaves are producing blister-like structures, that is probably caused by edema. 

It is a condition where the cells inside the plants rupture as a result of water pressure. This pressure happens when the inflow of water in the plants is greater than its outflow. 

Edema normally happens when the soil is overly moist combined with high humidity and low temperatures. During these times, slower transpiration causes the plant to lose less moisture.

Quick Solutions:

Edema happens as a combination of unfavorable factors in the environment. While we cannot control the environment, there are ways to mitigate its negative effect. 

  1. Allow the soil to dry in between waterings. Again, aloe vera doesn’t need much water because it has enough supply in its leaves. Always check the soil moisture before watering again. 
  2. Space out your plants. This will help provide good air circulation. Plants that are grouped together are often surrounded by high humidity. 
  3. Increase exposure to sunlight. This helps hasten the release of moisture from the plant. 

Once the environmental conditions go back to normal, the plant will naturally recover from edema. So, there is no need to worry a bunch about this. 

Excess Light

Aloe vera likes receiving bright light. However, it doesn’t want direct exposure to strong intensities of light.

Sustained exposure to the sun, especially during summer, can easily scorch the leaves leaving them with brown spots.

In some cases, leaving your aloe vera under sunlight will cause the whole leaves to turn brown.

An artificial light source may also cause the same damage if it’s positioned very close to your aloe. 

Quick Solutions:

Here are effective ways to fix the brown spot problem caused by excessive light:

  1. If your aloe vera is located outside, bring it indoors. Clearly, prolonged exposure to direct sunlight is not helping the plant. 
  2. Choose a western or southern window. Place your aloe plant near that window but maintain enough distance so the leaves don’t touch the glass.
  3. Provide a sheer curtain to serve as shade when light intensity gets too strong. 
  4. If artificial light is provided, keep it at a distance of at least six feet away from your aloe vera plant. 
  5. Limit sunlight exposure to at most 6 hours. You can have your aloe taste the sunlight but make sure it doesn’t exceed the maximum hours allowed. And of course, do not do it everyday especially when it’s summertime.

Temperature Stress

Temperatures between 55-80°F (13-27°C) are ideal for aloe vera. It prefers a warmer environment to a colder one. Changing temperatures are normally tolerable if the condition doesn’t last that long.

If the temperature drops drastically, your aloe vera will experience stress due to prolonged coldness.

When the winter is closely approaching, the temperature specifically during the night gets really low. That is one probable reason why it is suddenly showing brown spots. 

Quick Solutions:

The normal temperature inside our homes is normally suited for the growth of aloe vera.

However, some adjustments must be done to avoid temperature stress among your plants. 

  1. Pull the curtains during the night. The temperature normally drops in the evening so make sure to use the curtains to protect your aloe from the cold radiating through the glass window. 
  2. Add extra light. Light emits heat which in turn adds warmth to your plant. During times of cold weather, make sure that there’s an extra source of light for your aloe. 
  3. Reduce watering. Plants would lose less water when the weather is cold. This is because evaporation happens at a slower rate. Save your aloe by not adding extra moisture. 
  4. Avoid cold drafts. Your air conditioner or cooler might be situated in close contact with your aloe plant. Remove your aloe plant from that location.

Pest Infestation

While it may not be a common occurrence, the reason for the brown spots you see on your aloe may be caused by pests.

Yes, they do attract unwanted organisms too such as mealybugs and aphids. These pests feast on the fleshy leaves of aloe vera by sucking on them leaving lesions afterward. 

The tiny lesions will turn brown after some time. If the aloe plant is heavily infected, more brown spots will be visible. 

Quick Solutions:

The pests of houseplants are generally easy to manage. Following are some easy solutions to try. 

  1. Spray them off with water. Use a little pressure to swipe off the pests on the surface of the leaves. Don’t forget to let the foliage dry before bringing it back indoors. 
  2. Wipe it off with alcohol. Using a cotton ball soaked with rubbing alcohol, wipe the infected portions. This will instantly kill the pests. 
  3. Apply horticultural oil. Diluted neem oils mixed with insecticidal soap will do the magic. It would be good to have a handy bottle of this solution to spray on plant parts affected by pests. 

Fertilizer Problem

Aloe vera is not a heavy feeder so it does not need much fertilizer. In fact, it will survive even without the consistent application of fertilizer.

Overfertilization is a possible danger that may cause brown spots on the leaves of your aloe. 

If you are heavily dependent on using inorganic fertilizers, there is a tendency that the soil will develop a crust on its surface because of the salt build-up.

These salts will draw away water from the roots making it difficult to transport the nutrients needed by the plants. 

As a result, your aloe will incur root injuries and leaf burns. In worst cases, the plant may even die a quick death. (source: University of Massachusetts Amherst)

Quick Solutions:

Overfertilization may sound terrifying when first heard, but there are definitely ways to save your aloe from this situation. 

  1. Leach off excess salts with water. Applying six inches of water will remove half of the fertilizer salts. You can do this successively within the day allowing enough interval for the water to drain.  
  2. Refrain from fertilizing your aloe. Sometimes, it would be better to not fertilize at all especially if your plant is visibly healthy. If ever fertilizing is needed, do it not more than once a month.

Poor Air Circulation

The lack of sufficient air circulation results in high humidity around the plants.

For tropical species, this is beneficial because they need a more humid environment in order to thrive. However, this condition is not good for succulents like aloe vera.

Poor air circulation would trap more moisture in the air. In turn, the aloe vera plant will find trouble releasing its own moisture in the air because it’s already saturated. 

Quick Solutions:

Poor air circulation is pretty much easy to handle. Here are the things that you could do:

  1. Provide ample space in between your plants. If your aloe vera is grouped with other plants especially tropical ones, then it’s time that you remove it from the batch. Place it somewhere a little isolated. 
  2. Open the windows. Let the fresh air come inside your homes. It will encourage good airflow. 
  3. Use an exhaust fan. If you’re struggling with getting fresh air because you don’t have good ventilation, then an exhaust fan would be of great help. Turn it on. 

Humidity

High humidity is not favorable to aloe vera. Remember that it’s a succulent plant that is more accustomed to a dry condition.

High humidity slows down the transpiration rate of the plant. It will make your aloe more prone to rotting. 

Apart from that, the moist environment will also encourage the growth of pathogens. The plant will then become more susceptible to diseases. 

Quick Solutions:

To prevent your aloe vera from suffering the downside of high humidity, here are some tricks you could apply. 

  1. Find a dry and warm location. The area where you place your aloe vera will mean a lot. To avoid high humidity, don’t place your aloe in kitchens or in the shower room. 
  2. Make sure it receives bright light. The presence of light helps the plant to lose more moisture. 

Improper Watering

One thing you have to always remember with Aloe vera is that this houseplant is packed with so much moisture inside its body.

It’s succulent with fleshy leaves meaning it can withstand long periods of drought. Constantly watering your aloe is not a good practice. 

Too much water is the primary cause of root rot in all plants including aloe vera. Damaged roots result in inefficient transport of water and nutrients to the leaves. Thus, it’s not surprising that the cells of those leaves eventually die.

Quick Solutions:

If you notice that your aloe vera is suffering from overwatering, here are some things you can do to save your plant. 

  1. Allow the soil to dry. Overwatered aloe plants would have wet and soggy soil. You have to ensure that the excess water in the soil will hastily evaporate by exposing it to the sun.
  2. Hold back watering for at least two weeks. The roots would need time to recover from the stress brought about by excessive irrigation. Don’t worry because your aloe won’t mind experiencing drought. 
  3. Repot if necessary. There are times when the damage of overwatering is severe and you need to transfer it to a new container.

Remember to cut down the damaged roots before planting them again using a well-draining potting mix.

Frost Damage

The stems of aloe vera are filled with water. This is where they store extra moisture to survive the long dry periods. However, this water will have the tendency to freeze during cold temperatures. 

The sudden freezing of the water inside the leaves will damage the tissues of the plant. That’s why you’ll see some portions turning brown. That means that those parts died out of the frost damage. 

Quick Solutions:

There’s no redemption when the plant gets damaged by the frost. The affected portions will surely die. But that doesn’t mean your whole plant will die as well. 

Here are some ways to save what remains of your aloe plant after the frost. 

  1. Cut the damaged portions. Those leaves that have turned brown due to the frosting should be removed. They’ll eventually rot anyway. 
  2. Relocate your aloe. Find a warmer place for your plant. Avoid locations where the temperature gets really low especially during the night. 
  3. Provide insulation. Cover your alive vera with cotton sheets or blankets to provide warmth around it. 
  4. Switch on the artificial light. When the temperature is cold during the day and there’s no enough light coming from the sun, use the room light to dissipate the coldness inside.  

How to Prevent Brown Spots on Aloe Plant? 

Knowing all the possible causes of brown spots in your aloe, for sure you now have enough understanding of what you should and should not do when tending for this plant.

Now, let’s dig into some of the most important ways to prevent these brown spots from recurring.

Choose the best planting material. 

Start with healthy plants. Pick the one that is vigorous in appearance. The leaves must have a vibrant green color without any sign of a blemish. 

Never ever pick a diseased aloe vera. It will just cause you more trouble in the future. 

Always provide bright light. 

Light will do so much to your aloe. Apart from helping your plant produce food, it also aids in hastening the transpiration rate, increasing the temperature, and making the surrounding environment dry. 

We know that aloe vera loves an arid place. Just make sure that the exposure to sunlight is indirect. We know that excess light is not that good. 

Water deeply but rarely. 

The Aloe plant does not need a regular drink. It gets thirsty very rarely but when it does, it needs quenching. Make sure to water the plant deeply so it will be able to replenish its water reservoir. 

When it comes to aloe vera, imagine yourself filling up a drum of water. Once the water is depleted, you fill it up to the brim. And then, you wait again until the drum is almost empty. 

Prepare for the cold weather. 

Aloe vera is very sensitive to cold. The leaves are tender and will easily get damaged by frosting. When the weather is changing, be ready to protect your aloe vera by relocating it, adding a supplementary light source, covering it with insulators, and the like. 

Opt for slow-release organic fertilizers. 

Overfertilization often happens when using readily available fertilizers such as inorganic ones. Since aloe vera is not a heavy feeder, it will survive even with less fertilization. What you can do is incorporate slow-release fertilizers into the soil. 

Slow-release fertilizers are organic sources of nutrients. Since they’re not readily available, it will take time for the nutrients to be released on the soil. That way, the danger of salt build-up is prevented. 

No misting and no overhead watering. 

Your aloe vera won’t appreciate that extra moisture. Reserve the misting to your tropical houseplants. Keep your aloe plant dry as much as possible. 

A highly humid environment is not friendly to your aloe. Keep it down so the plant will not rot and develop diseases. 

Bring it outside from time to time. 

It would be good to expose your aloe vera to an outside environment when the weather is good. Let it enjoy the sunlight (not more than 6 hours). Allow it to breathe in the fresh air. 

You can do this from May to September when the season is generally fair. After that, you have to bring your aloe plant inside the comforts of your home to avoid the cold temperature. 

Keep the pests away. 

Although aloe vera is rarely affected by pests, we cannot downplay the possibility of them being around.

Make it a habit to regularly inspect your aloe for any presence of mealybugs and aphids. It is better to spot and remove them while they are few and manageable. 

As much as possible, avoid using harmful chemicals such as pesticides or insecticides on your houseplant.

We do not want to risk our own health just to keep those pests away. You can manage them using those household remedies instead. 

Use a well-draining and disease-free potting mix

Aloe vera will do well in a potting mix intended for cactus and succulents. These mixes are well-draining and there’s an assurance that the water won’t get stuck in the pot.

Also, do not forget to choose the mix that has been previously sterilized. This is to ensure that no soil-borne disease will develop. Healthy soil is a prerequisite to a healthy plant. 

Care and maintenance of an aloe vera plant are very easy as compared with other houseplants.

If you ever encounter problems such as seeing brown spots on the leaves, investigate the possible causes. From there, you will surely find a way to find solutions to the problem. 

Always remember that your aloe vera is a tough plant. So, there is a high chance that it will survive the odds. Now, best of luck!