Aloe Veras are easy to grow and can endure dry conditions. Although they are known for their healing properties, Aloes are not resistant to some conditions. They will encounter problems like black spots if neglected. But why do they have black spots? Let’s find out.
The black spots on the Aloe Vera leaves are signs of fungal and bacterial infections like soft rot, leaf spot diseases, or basal stem rot. Besides these, the leaves will also have black spots due to overwatering, scorching sun, and sap-sucking bugs like mealybugs and aphids.
This guide has everything you want to know about Aloe vera developing black spots. I will share the reasons and simple ways of dealing with it. So, let’s get into it without further delay.
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Why is my Aloe Vera plant getting black spots?
There can be various reasons behind black spots on leaves.
Let’s have a look at the probable reasons and discuss them in detail:
Exposure to the scorching sunlight
Aloe Vera grows best in a sunny environment.
But, they too will get scorched if exposed to the direct scorching sun, especially during the summers.
This happens when you suddenly shift the plant growing under a partially shaded area to a place with direct sun exposure without acclimatizing.
Or, you are shifting an indoor plant outdoors to a sunny spot.
Another situation when a black spot occurs is when you keep artificial lights too close to the indoor plants.
It works the same way as scorching sun.
What is the treatment?
If you want to shift your plant outdoors for sufficient sunlight, you should acclimatize.
This also applies to those outdoors Aloes growing under partially shady or medium-light areas.
- First, shift the indoor Aloes under a partially shady area outside for some days.
- Let them have 4-5 hours of light per day.
- After that, keep them under the direct sun for only 3-4 hours and slowly increase the timing. Morning would be best.
- You can also relocate the indoor Aloe Veras to a south or west-facing window with transparent curtains. The curtains will filter the light and save the plant from sunburn.
- For shifting an outside aloe from medium sunlight to full sun, let it stay under the sun for only 2-3 hours for the first few days and bring it back to its place.
- Slowly increase the timing.
- It would be great if the plant receives the direct morning sun and shade during the mid-day and afternoon.
- Fix transparent shading nets or clothes to protect the plant from the scorching sun.
- If you are using artificial lights for indoor plants, keep a distance of at least 2 meters between them both. They should neither be too close nor too far.
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Aloes require very less water compared to many other plants.
Aloes thrive in a dry and warm environment with low moisture levels.
Moreover, they store water and have enough to withstand high temperatures and dry weather.
But excessive water can make the Aloes rot.
Once the excess water reaches the roots, it will suffocate them and cut off the water and nutrient transportation to other parts.
Over time, the roots will become mushy and begin to rot.
Root rot is a disease caused due to prolonged overwatering.
It will make your leaves develop black spots over the leaves and stems.
Lack of water and nutrients also causes the sudden appearance of black spots.
Poor drainage in the soil or container is also responsible.
You should give a check on that too.
How to improve watering habits?
To save your plant from having such black spots, you must improve your watering habits.
It is the best way to fix the problem and prevent it from further appearing.
There are many rituals to follow.
- If you are a beginner, the best way to water the Aloes is to check the soil’s moisture level before watering.
- Your Aloe Vera plant is ready to take water if the soil’s top 2-3 inches is dry.
- Once you excel in this, you can follow the routine as per Aloe’s needs. Generally, Aloes should be watered once in 2-3 weeks. This frequency will change depending on the season, climate, plant size, maturity, soil, etc.
- Even if you follow a routine, never stop checking the moisture level.
- Watering issues will also occur if the soil or pot promotes poor drainage. Use cactus or succulent potting mix. To make the soil mix yourself, add porous ingredients like coarse sand, perlite, pumice, gravel, stones, etc., to improve drainage.
- A planter with drainage holes is mandatory. Additionally, choose a wide pot and not a big or deep one. The size should be 1/3rd bigger than the plant. Terracotta can wick away moisture and keep the plant dry.
Since Aloes are adapted to grow in a warm temperature, they cannot tolerate cold.
A cold temperature can decrease the rate of evaporation, which develops a heavy amount of moisture in the Aloe Vera soil.
High moisture levels for prolonged periods in such a condition can attract pathogens and give rise to pest and fungus infestation.
The Aloes should stay within a temperature ranging between 55°F-75°F.
Exposure to extreme cold weather can also give the plant frost and freeze damage.
These damages can injure the plant cells and tissues, which are nearly impossible to cure.
How to maintain the correct temperature?
Your Aloe Vera should get insulation during cold weather.
- If your area receives such cold, grow them in containers to shift them indoors.
- If your plant is in the ground, cover them with frost cloths. You can also add some pebbles to the soil bed. This will trap the warmth in the soil and prevent the cold from reaching the roots.
- If the given insulation is insufficient, bring the Aloes indoors. Use artificial lights inside if the plant doesn’t get enough sunlight. Keep the light 2 meters away from the plant.
- Letting have sunlight for at least 3-5 hours also keeps Aloes warm. Place them near a sunny window. The south or west-facing window would be best as it gives maximum sunlight during winters.
- Scale back watering. The growing medium should stay almost dry in winters. Watering them once a month will be enough for hydration.
- Remove the spotted leaves that seem unable to recover. It prevents spreading.
Aloes love dry and warm conditions and hate damp and cold weather.
That’s why Aloes don’t struggle in low humidity.
But, there is a limit.
Extremely low humidity can develop annoying spots.
Extremely dry air can make the plant lose moisture faster.
An extreme lack of humidity will pull out the moisture powerfully from the plant and the soil.
Without enough moisture, the plant won’t be able to perform proper photosynthesis.
Besides having those unwanted black spots, the plant will undergo dehydration, wilting, and dry and crispy leaves.
How to increase the humidity?
- Shift your plant to a humid area. But the level should remain within 40-50% only and not more. Excessive high humidity can cause mold.
- You can spray some water on the leaves to let them have the moisture they need. But don’t spray too much water. Check if the water has dried.
- You can use a humidifier for indoor Aloes to increase the humidity.
- Other ways to increase humidity are keeping pebble trays under the container or water trays around the plant. But these might increase humidity greatly if continued for extended periods. But, still, you can try for a short time.
It occurs more with the outdoor Aloe Veras than the indoors.
But, that doesn’t mean your indoor plant is safe from these critters.
Mealybugs, aphids, aloe mites, and several other bugs can leave black spots in Aloes.
These sap-sucking bugs pierce the leaf and suck all the sap.
These pierced areas dry out and darken, due to which your leaves have dark spots in places.
- Mealybugs are tiny, white bugs with waxy bodies.
- They suck the xylem sap of the plant and secrete honeydew.
- This sticky honeydew can destroy the plant structure and develop sooty mold.
- The leaves will have small pale spots which, later on, will darken.
- Aphids have pear-shaped heads with light green bodies.
- They live underneath the leaves. They, too, feed the same way as mealybugs and excrete honeydew.
- Aloe mite infestation cannot be seen unless the plant is affected. They feed on chlorophyll and create an obstacle to smooth photosynthesis. Your leaves will have small yellow spots, darkening over time and turning black.
- In worse conditions, the plant will develop multiple galls, a cancerous growth, and reviving would be impossible.
How to remove bugs?
- Dab rubbing alcohol in the infested area. The waxy body is the shield that the alcohol can weaken. Once the shield weakens, the bugs will fall and die.
- You can even spray it. Mix 3-5 drops of dish soap with one cup of alcohol in a spray bottle and spray. Use it once a week until the problem solves.
- Spray Neem oil. It is safe, organic, and effective. It also helps prevent fungus attacks. But don’t expose your plant to the sun while spraying neem oil. It can burn the leaves.
- If the infestation is severe, use insecticidal soaps and other chemical insecticides and pesticides to kill them.
- In this case, you don’t have to use any chemical products. There are many natural predators like ladybugs and mantis. Release them to the soil bed. They will feed on them and make your plant completely bug-free.
- You can dab rubbing alcohol on the infested area.
- Insecticidal soaps like Safer soap and Castile soap will also help. Use them once a week until the problem resolves.
- First, isolate the plant to avoid spreading.
- Ladybugs and beetles can help. They love to feed on them.
- Use a mixture of alcohol to the place where you suspect the infestation.
- But, remember, this will only help if the infestation is caught at the initial stage. If the mites get into the plant, it will be impossible to save it.
- If your plant has got galls, dispose of those particular areas. If there are maximum galls, you need to throw the plant.
Aloes will get this problem mostly in winter or extremely hot and humid climates.
The plant generally suffers fungal diseases if it has high moisture content.
Maintaining good drainage, correct watering habits, and low humidity levels are essential.
Below are some diseases, the reasons for their appearance, and their symptoms:
Leaf spot disease
Black spots in the Aloe Vera leaves occur mostly due to this disease.
The fungus names Alternaria Alternate destroys the tissues, cells, and antimicrobial defense system of the plant.
This fungus loves to stay in prolonged moist areas.
- The leaves will first have small, dark brown spots
- Over time, the spots will grow big and turn black.
- The spots will continue to grow bigger until the leaves decay.
This disease is caused by the fungus named Colletotrichum gloeosporioides.
It enjoys warm and wet conditions and gets spread faster with water splash.
- Dark green oval-shaped spot on the leaves at first
- The middle of the lesions becomes brown over time and changes to a dark round spot.
It is caused by a fungus named Phakopsora pachyrhizi.
This fungus travels in the wind, gets transferred by the wind, and enjoys moist conditions.
The fungus feeds on the outer leaves and also produces spores that can end the life of your Aloe Vera plant.
- Yellow spots in the beginning, which later on turn black
- Orange spore masses on the underside of the leaves
- Plant dropping leaves
Basal stem rot
The disease is caused by mycotoxins produced by the fungus Fusarium.
The fungus comes out to attack mostly during the cold winter months.
- Initial signs are reddish-brown rotting at the base.
- Dark spots on the stems signify rotting in the stem.
How can I treat fungal diseases?
Leaf spot diseases
- The first and foremost step is to quarantine the plant to prevent spreading.
- Shift the plant to a location with low humidity. This will stop the constant development of moisture and keep the soil dry.
- Remove the infected leaves to prevent spreading.
- Apply some fungicide to the infected and cut part to ensure the complete removal of the trespassers.
- Don’t water the plant for some days and wait for the soil to dry out completely.
- When you start watering the plant, avoid splashing in on the leaves, especially the infected ones.
- Keep the surroundings neat and clean. Always dispose of the infected leaves in the dustbin and not near your garden. Never use these leaves in compost.
- First, isolate the plant and remove the infected leaves. It will avoid the spreading of pathogens.
- Always discard them in a dustbin.
- Spray some liquid copper once a week in the infected areas. Do this in the morning.
- Spray some Neem oil. It is safe and effective in getting rid of these types of fungi. Apply this once a week until the signs of Anthracnose diminishes. While spraying neem oil, don’t expose the plant to direct sun as it can burn the leaves.
- First of all, pause watering and let the soil dry out.
- If your plant is in the container, remove the excess water from the saucer.
- Shift your plant to a bright location with dry surroundings to let the soil dry faster.
- Avoid watering for 1-2 weeks or until the soil has dried out.
- Maintain adequate space between each plant for proper air circulation. It supports fast drying of the soil and prevents the disease from spreading.
Basal stem rot
Since the rot is in the stem, it is more severe than the other issues. It will be difficult to handle, especially if you are new to gardening.
But don’t worry, as I have shared the steps below.
Following the correctly can help revive your plant.
- You have to check the roots. Before that, don’t forget to isolate the plant.
- Clean the roots to have a clear watch on the roots. Mushy roots and stems are common symptoms.
- Cut off the infected roots and throw them quickly. There are chances of survival if your plant has some healthy roots.
- Remove the infected leaves and stems as well to avoid spreading.
- Now, repot to save the plant.
- Don’t use the same pot and soil since they are infected. Take a new container and make a new soil mix.
- Spray some fungicide to the roots before planting to avoid further fungus development.
- Don’t water them too much or expose them to the direct sun.
- Wait for a week to water them.
- Let them have indirect sunlight until they show signs of recovery.
- Slowly expose them to the direct sun by acclimatization.
Another disease that causes black spots is a bacterial disease.
Though the problem is less complicated than fungi, never ignore them.
That can damage the plant severely even with antimicrobial defenses.
The disease is Bacterial Soft Rot caused by the bacteria Pectobacterium chrysanthemi.
It enters the plant’s defensive enzyme and destroys the structure.
Though it occurs mostly in the root crops and vegetables, your Aloe is not safe from its lethal invasion if conditions are favorable.
The common symptoms are damp and dark spots in the leaves.
Over time, the spots will grow bigger and worsen.
The leaves will wilt and drop off, especially the lower leaves.
The soil also releases a strong rotting smell.
How to treat the disease?
- There is usually no proven treatment for Bacterial Soft Rot, especially if the plant is severely damaged. If most of the leaves are affected, throw them away.
- If there are few healthy leaves left, propagate. However, most people ignore it because the leaves shrivel.
- Find the pups to propagate. They should be healthy and big enough, at least 1/4th the size of the mother plant.
- Remove the pups and plant them in well-drained soil. Start watering after a week, and don’t expose the plant to the direct sun until they are well-established.
There are various reasons behind Aloe Vera leaves having black spots. Whenever you see the marks on your Aloe Vera, compare the reasons I have mentioned to check which particular problem your plant is facing.
After that, fix the issue quickly. Never delay in such things. The more you detain in treating the problem, the more your plant will deteriorate.
Give them enough sunlight and water only when the soil is dry. Ensure good drainage, maintain low humidity, protect the Aloes from cold and keep the surroundings clean to avoid pathogen infestation.