How Do I Get Rid Of Brown Spots On My Cactus?

Are you seeing any spots of brown on your cactus recently? It’s likely because of an issue that many suffer from with cacti and the results could be alarming. Cactus is renowned for its durability, however it is susceptible to attack at times.

Brown spots that appear on cactus are result of changes in the physiology processes. They can be caused by changes in the environment (light and humidity, temperature frost, as well as inadequate circulation of air) or poor management (overwatering and over fertilization) as well as biotic causes (pests and fungal diseases, etc.).).

To comprehend the reason why brown spots appear on your cactus, you need to understand the mechanism that is that causes them.

This article can help you overcome the issues which will reduce the possibility of your cactus developing brown spots.

How to Identify Cactus Brown Spots?

Brown spots can appear different depending on the cause and how long they’ve been there, and the extent of the damage was.

They vary in size, brown shade, and even their texture. They can dry out and appear like lesions, whereas others develop blisters.

Why Does My Cactus Have a Brown Spot?

Excess Sun Exposure

To maintain their vibrant colors, cacti require lots in bright sunlight. Light is also essential to produce photosynthesis, which creates food and helps with physiological functions.

In the future, exposure to the sun could cause burning and brown spots on your Cactus.

The sun’s excessive exposure triggers the defense mechanism of the cactus. It releases anthocyanin, which is a pigment that triggers it’s color to change from blue to violet. This color change is a sign of stress.

When exposing your cactus plant in direct light, be sure that you acclimatize it. This process should be done slowly.

1. Move Your Plant Indoors

Take your plants inside if outside. The cactus in your garden is having trouble taking on the extra light. The extreme light exposure can be reduced by moving it inside your home.

2. Provide Additional Shade

If the intensity of light inside is excessive it can result in scorching. To decrease the intensity, you’ll have to give the plant additional shade.

It is possible to do this with curtains or even larger plants to block out some light.

Improper Watering

The underwatering and the overwatering are both instances of watering that is not properly.

Cacti can tolerate drought conditions and water shortage isn’t an issue. It is important to be cautious not to overuse water.

Factors like the quality of the potting mix, temperature of the watering frequency, as well as humidity can all impact water usage.

It’s possible to drown your cactus if not vigilant. This can cause root rot to take place.

The brown, mushy spots that appear on the root are an obvious indication of root decay.

These spots are caused by the decaying plant’s parts that are beginning to degrade.

The reason for this is that root structures have suffered damage and they are not capable of transferring nutrients and water.

cactus next to laptop

Check How Moist the Soil Is

It is possible to tell if the soil is waterlogged by dipping your finger about an 1 inch beneath the soil surface. Make sure you’re using a high drainage capacity soil suitable for Cactus.

Soggy soil indicates that it’s received excessive amounts of water. The soil that is and dry on the skin is perfect for succulents and cacti.

Pest Infestation Causing Spots on Cactus

While I don’t see any insects infecting our cacti it’s not impossible to rule out an possibility of them being responsible in the dark spots that appear on our plants.

Pests usually infect cacti through sucking on plant tissue. In the process, the surface of the cactus is damaged by tiny wounds which eventually become brown.

Scales with armor ( Diaspididae) that consume plant fluids using straw-like mouthparts. They are an example of one of these insects.

Because they’re so tiny, they are difficult to spot. Therefore, you might not be aware of them until the plant starts to reveal signs of the damage they’ve caused.

Mites can also pose a risk. If they are allowed to grow, they can cause harm in the plants, making affected areas yellow or reddish-brown. (Source: University of California)

Inspect the Cacti for Any Presence of Pests

Since these creatures are small enough to not be seen with an untrained eye it is important to take the time to inspect your cacti for any stray insects.

Every now and then you may want to employ this technique to prevent the spread of diseases. Examine all the plants in your home to determine whether the pests haven’t found an appearance elsewhere.

Temperature Stress Can Damage the Cells

Extremely low and high temperatures can cause stress to your Cactus. Rapid temperature fluctuations are not advised for cacti as they can cause shock to the plant.

The optimal temperature is between 45 and 85 degF (7-29 degC). The tissues of your cacti can get damaged due to extremes in temperature.

The result is usually quick. This is why you’ll be able to spot the signs of damage, like brown spots within the shortest amount of time.

1. Relocate the Cacti Pots

Be cautious when your cacti plant is located near a window because the glass could cause the plants in your pot to heat up or overcool themselves.

Moving to a location where temperatures are more stable will help reduce the effects of stress caused by temperature.

2. Provide Insulation When Cold

The insulation of your cactus is essential to protect it from damage. The evening temperatures tend to be cooler, however when winter months are upon us the temperatures can drop even lower.

A little warmth can help it cope with dealing with the abrupt decrease in temperature.

Fungal Disease

Other pathogens and fungi can trigger disease on your Cactus. It is extremely difficult to eliminate an infection after it has gotten hold of your cactus.

Cactus are permanently damaged by the fungus Colletotrichum (Gleosporium) species. the most frequent fungus that causes Cactus anthracnose.

The infected area initially appears to be damp and lighter brown. In time the spots will spread over all of the plant. Cacti plants that are infected by fungal diseases have an increased chance of dying.

1. Discard Infected Portions

To stop the spread of the disease, it’s recommended to cut immediately the affected areas and then eliminate the affected areas.

There could be instances when you have to eliminate all the plants. Anthracnose can be difficult to manage.

2. Apply Fungicide

Chemical control is a fast solution to the fungal issue. Fungicides are either curative or preventive in the natural.

The use of preventive fungicides is recommended prior to planting, while curative fungicides are recommended when symptoms begin to appear.

3. Avoid Humid Conditions

The pathogens, like fungi thrive in humid environments. There is a higher chance of developing fungal illnesses when the humidity levels are high.

Cactus is not a fan of humid conditions, so it is essential to keep the climate under control.

Rust Spots on Cactus

Rust is among the conditions that can manifest in cacti, specifically the pear of the cactus. Puccinia Opuntiae is a kind of fungus, is the one to be blamed for.

According the FAO, “produces yellow-orange pustules on the surface of cladodes or fruits” of the Cactus. (Source)

As the rust spot dry it will leave a gap. The site of infection will grow until the plant is completely affected. In the event of a delay, it could cause the loss of the entire plant.

1. Remove and Bury the Infected Clalode

This is the best way to deal with Cactus rust disease. When you begin to notice symptoms it is imperative to eliminate the affected areas as quickly as you can to stop the disease from spreading.

2. Isolate the Infected Plant

Plant diseases are spread like wildfire. Other plants are also at risk of getting infected if you’re not vigilant. The isolation of the plant can aid in the fight against disease.

3. Apply Preventive Fungicide on Other Cacti

If there are other types of cacti that aren’t been affected, it’s best to be sure to spray the cacti with a fungicide.

It’s good news since the market already has organic and non-organic alternatives.

Be cautious when using fungicides, and follow the instructions in the label that accompany the.

Fertilizer Overdose Can Burn the Cactus

Cacti aren’t large feeders, which means they don’t require fertilized constantly. If you’ve fed the plant too much it’s likely to see dark spots appearing on stems, which is a sign of damage. In addition, too much fertilizer can cause the cacti’s tissue to be burned.

Salts may also build up in soils due to over-fertilizing. The salts can alter soil’s pH and decrease its number of beneficial microorganisms.

Roots may also be damaged and stop functioning properly. The cactus may turn brown due to this.

1. Leach Or Rinse Off Excess Fertilizer

It is possible to quickly remove the fertilizer that is too much by leaching it out with water. Pour the water thoroughly into the pot until it is drenched. Then wait for a couple of hours before repeating the process time.

2. If Necessary, Repot in Fresh Potting Soil

To prevent overfertilization it’s sometimes essential to repotte the Cactus to avoid overfertilization.

If the leaching doesn’t work then you’ll need to prepare soil for planting the plant. Before placing it into the soil examine the roots for any indications of damage, and then trim them , if needed.

Inadequate Air Circulation

Air circulation issues are an issue that is common in an indoor space that is enclosed. Insufficient airflow can prolong the dampness particularly if you’ve recently given your plants a watering. We know that an environment that is damp invites pathogens to flourish.

1. Open the Windows and Doors

It is possible to increase the circulation of air by closing the doors and windows for a short period of time. This will not only benefit the health of your plant, but it can benefit you as well. In allowing fresh air in from the outside, you’re forcing your air to move inside.

Let your cacti breathe fresh air outdoors. Set it in an open space with ample light. It will assist in the removal of the excess moisture that is accumulating on your Cacti.

2. Make use of the Exhaust Fan

Exhaust fans remove the smells, fumes and moisture from the interior of your house and exchanging them with the outside.

It helps in the improvement of air circulation within the space. Fresh air is now able to be introduced into the room once the trapped air is pushed out.

High Humidity Triggers Fungal Growth

Cactus grows best in dry, arid environments like deserts. If the humidity in the atmosphere is very high, Cacti can be susceptible to decay.

Overwatering and high humidity can cause a variety of deaths. The growth of pathogens is also increased. Unfavorable conditions can affect the overall health and wellbeing of your Cacti.

What to Do?

Beware of areas that are humid in your house, like bathrooms and kitchens, since they are the areas that are most humid.

It is possible to cut back on watering in the case of an environment that is very humid. Due to the moisture content in the atmosphere, transpiration will definitely be slow.

If you sprinkle water on the soil, the cacti will struggle to absorb it, which results in an overwatering.

Frost Damage

Cacti aren’t frost-resistant. In winter they are especially susceptible to damage caused by cold temperatures.

Due to their high moisture content inside They are prone to freezing even at very low temperatures. There will appear as brown spots on various areas of the plant when it melts.

1. Relocate the Cacti During the Night

The temperature at night is lower than the daytime temperature.

The chill of the night will definitely impact the plant , especially if it’s situated near a glass window. If this is the case, you’ll have to move the plant to a more comfortable place.

2. Protect the Cactus Plant by Keeping It Warm

Covering cacti with cotton sheet is a good alternative when temperatures are colder. This will prevent plants from getting frozen, by creating an environment that is warm surrounding it. The thickness of the insulation be is contingent on how cold the outside temperature is and therefore, make sure that it’s sufficiently thick.

3. Get the area warm by putting on a light

Cacti can benefit from the additional warmth that is provided by artificial lighting. In winter, you can group your plants and place a 100-watt light over them. Be sure that there is enough space for the lamp and don’t allow it to get in contact with the cover of your sheet.

How to Prevent Brown Spots on Cactus?

Begin with Cacti that are disease-free

Make sure you choose an obedient and healthy cacti when you purchase. Check for the presence of brown spots, and if you spot any, do not buy it. Beginning with healthy plants can help you save a lot of effort.

Use Clean and Good Quality Potting Soil

The type of potting mix that you choose to use is crucial to the growth of your Cactus plant.

If you’re not sure what to use for your mix, use the cacti mixes readily available at garden centers. It’s essential that the mix is cleaned (pathogen-free) and well-drained.

Find the Best Location

It must be well-lit, less humid, and more comfortable. These conditions are perfect for cacti to flourish.

There are instances when conditions dramatically change, so you need to use some tricks, such as using exhaust fans or artificial light sources and so on.

Regulate Water and Fertilizer

Cacti will not require a lot of either input. It is better to provide the nutrients in controlled amounts rather instead of overdoing it. In excess, it can cause harm to the overall health and well-being of your Cactus.

Use Fungicide as Preventive Measure

Apply fungicides on the soil to stop the development of fungal organisms. This can reduce the possibility of developing fungal illnesses.

It is possible to use baking soda to create a natural chemical fungicide, or you can purchase the commercially accessible organic as well as organic fungicides.

Check and Remove Pests Regularly

Check your cacti on a regular basis and look for foreign species. If you are quick to identify these, you can stop the spread of further harm.

There are numerous ways to manage pests, including chemical, mechanical physical, and chemical techniques.


How Do I Get Rid Of Black Spots on My Cactus?

Cactus with black spots occur as a result of stress caused by abiotic or biological causes.

There are a variety of reasons for your cactus to have black spots. The first thing you need to determine is the root reason. The treatment options for black spots differ based on the cause.

The abiotic causes like excess light, excessive watering and over-fertilizing, high humidity and cold temperatures can be controlled by using simple methods. If the issue is due to pathogens, it can be more difficult.

Can You Revive A Brown Cactus?

It is contingent on the degree of the browning. When the bulk of the body is already brown, you may as better just let it be. It’s difficult to attempt to save a lost cause.

If the browning is not too severe it is still possible to keep the plant. Examine how the cacti react to the treatments you’ve used. If the browning is lessened then you’re on the right path.

What Does An Overwatered Cactus Look Like?

A cactus that has been overwatered will have brown parts that feel soft when touched.

Roots are dented, and its base is typically weak and rotten. If you attempt to remove it from the soil, the root will easily separate away from roots.

Brown spots appearing on the cactus is a sign of the presence of an internal issue. This is a warning sign to be aware of. If you didn’t, you’d be far behind to see the harm.

Final Words

To keep your cacti healthy, preventive is the best option. Be aware of the fundamental requirements for growth and adhere to it as long as you can. Make sure you are aware of any the environmental conditions and adjust when necessary.



Went from a bad gardener to a half-decent one over 10+ years. Super happy to share my tips and tricks with you :)