How to Remove Brown Spots on Cactus

If your cactus plants have brown spots you will want to learn about the common causes and effective ways to remedy the affected areas. In order to find out how to remove brown spots on a cactus, It’s a good idea to explore some of the most common problems that may cause brown areas to appear.

Cactus plants that are receiving too much sunlight, sitting in wet soil, or experiencing a lack of water can lead to a rotting cactus. Cold temperatures, pests, dry rot, and root rot can also cause trouble for your plants.

To encourage new growth and set up your new plant for success, follow these tips for how to get rid of brown spots on cacti.

How to Remove Brown Spots on Cactus

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Different Types of Brown Spots on Cactus

The cause of the brown spots can vary but you may be able to figure out the exact cause of cacti turning brown through the process of elimination. Since there are different types of brown spots that can form on your cactus, it’s best to figure out which type your cactus is experiencing.

You may notice the leaves turning yellow or brown, this can be due to the pot being too small, too much light, or even the wrong soil type, although watering issues are usually the culprit.

The location and type of brown spots can help you determine your approach to rid your cactus of brown spots.

How to Identify Root Rot On Cactus

One of the most common reasons for a healthy cactus to turn brown is root rot. This usually starts at the base of the plant but it will eventually take over the whole plant.

You can identify root rot by feeling the stems to see if they are soft, this can happen before they turn brown. If you notice your cactus turning yellow, this is most likely root rot, also known as stem rot. It will eventually turn brown and can actually kill your plant in as little as four days.

How to Identify Cactus Corking

Cactus corking is a normal part of an aging cactus, it can resemble tree bark and isn’t usually something to worry about. . It usually begins at the bottom of the plant and moves upward. It can grow on the stems and usually appears as skin splits along the central vein.

Corking exposes the plant tissues which can make it more susceptible to other issues but other than changing the plant’s appearance, this isn’t something to worry about.

How to Identify Sun Damage on Cactus

Sun damage can also cause brown spots on your cactus. This can happen anywhere on the cactus but in my experience, it usually happens on the top of the cactus first. Although this may be due to the placement of my plants since I keep them directly below the window.

A common misconception is that a cactus plant should be left in full sun and that it is impossible to give them too much light. Unfortunately, that is not true, just like with people, your plant can get sunburned from too much direct sunlight.

If your cactus lives in bright light, the brown spots can be a sign of sunburn. This can appear in the form of brown spots, black spots, or patches anywhere on your cactus.

How to Identify Mealybugs on Cactus

Although mealybugs are small red insects, you will be able to notice if this is a problem for your cactus by looking for fluffy white sticky mounds.

This can appear on the base, stems, or roots of your cacti plant.

How to Remove Brown Spots on Cactus

What Causes Brown Spots on a Cactus?

Temperature

In the colder months, even indoor plants can get frost damage. This is usually due to being inside of a window sill or up against it. While this may be the best place for your Christmas cacti to get some sun, it may not be the best temperature to leave your cactus in.

If your plant is touching a frosty window and is susceptible to poor air circulation it may be a good idea to move it away from the window during the Winter. If this is the best sunny spot for your cactus to live try your best to mitigate any issues with drafts that may be affecting the temperature of your cactus.

Watering Issues

Excess water can lead to a lot of problems for these prickly plants. If you find that they are constantly sitting in damp soil, you are probably overwatering your cactus.

During the growing season when we are most likely to experience warm temperatures, your plants may require more water than in the cold weather.

Wet weather will also mean you will not need to water your plants frequently due to the excess moisture in the air. During times of high humidity, it is nearly impossible for your plant to dry out.

Before adding more water, check for dry soil. If you have overwatered your plant it may be best to empty the pot completely and replace the moist soil with fresh soil.

Pests

Pests can be a problem for plants of all sizes, even a small plant can be impacted.

A common pest is mealybugs and if you spot these on your plant you need to immediately isolate it. This will prevent them from spreading to your other plants which can happen pretty fast.

Small white spots can mean you have spider mites or other scale insects. These critters usually are accompanied by tiny webbings.

Red spider mites are a common pest infestation that can also cause problems for nearby plants so be sure to isolate them as soon as you determine that this is the problem causing your cactus to turn brown.

flowering cactus

Fungal Disease

If your cactus is turning brown it could be due to fungal infections. You can determine if this is an issue for you by checking the surface of your plant for lesions. They can appear as light brown spots, yellow spots, and even black spots.

Plants with constant wet stems or pads are usually the most affected.

Powdery Mildew

Powdery mildew is a common problem for a cactus that has been sitting in excess moisture for a long period of time. You will be able to catch this early if you know what to look for. This mildew begins by forming white fuzzy patches on the leaves and is usually a quick fix.

I had good luck removing this from my Christmas cactus just by improving the airflow. I found that my pot did not have proper drainage and my home was very humid, this combination lead to me becoming very familiar with this common cacti ailment.

Luckily I caught it pretty quickly and was able to remedy the situation before it got any worse.

How to Remove Brown Spots on Cactus

Overfertilization

Overfertilization can also lead to brown spots on a cactus. It is recommended to use a 5-10-10 blend or 10-10-10 fertilizer diluted to 1/4th strength for a cactus, about once a year.

A general rule with many varieties of cacti is that it is best to under-fertilize rather than risk overdoing it.

Cactus plant care

How to Remove Brown Spots on Cactus

Once you have figured out what is causing the small brown spots to appear on your cactus plant you can determine what is the best way to handle the problem.

The good news is that there are many easy solutions to combat common problems that lead to a brown cactus.

How to Remove Brown Spots on Cactus Caused By Sun Damage

Immediately move your cactus to a location with partial shade to avoid brown patches from forming again. Indirect light may be the best thing for your indoor plants, give them a spot where they receive 5-6 hours of indirect sunlight each day.

How to Remove Brown Spots on Cactus Caused By Root Rot

To remedy root rot, remove the plant from the pot and put it into a new pot or just replace the soggy soil. You want to be sure to use well-draining soil to prevent it from happening again.

Cactus rot can become a recurring problem if you are using the wrong soil, if this is a repeated issue for you, try a sandier mix.

How to Remove Brown Spots on Cactus From Fungus

To treat fungus, you can apply a fungicide solution to the fungal lesions or infected areas. This will eliminate the spores and prevent them from spreading and doing any further damage to your cactus plant.

Use the fungicidal spray or solution to penetrate the plant tissue. It may be a good idea to use a sharp knife to remove any of the affected areas before treating the rest of the plant.

You can use a variety of different fungus solutions or neem oil to help combat the issue. Add to a spray bottle and apply to the plant according to manufacturer instructions.

How to Remove Brown Spots on Cactus From Pests

When you find bacterial infections or common pests on your cactus plant’s leaves, it’s best to isolate the plant. While the problem could be due to a variety of causes it is best to prevent the possibility of bacterial diseases spreading to your other plants.

It’s also a good idea to clean any tools you may have used on the dying cactus with insecticidal soap to prevent permanent damage to other plants.

To treat the cactus, spray the entire plant, including all of its leaves, with the insecticidal soap mixture.

You can use a cotton swab to cover the affected area to kill the pests if you don’t want to spray but it is recommended to use a pesticide spray rather than just rinsing the plant off.

You can remove mealybugs by using a cup of warm water with 2 drops of unscented dish soap. Get an old, soft toothbrush to scrub them off, and be careful not to press too hard causing damage to your plant during the mealybug removal process.

Repot Your Plants

Don’t use as much water in high-humidity conditions and be sure to add a drainage hole to your pot.

Using soil with a nice balance of organic matter and aggregate can also help to promote healthy draining in your pot.

Use soil with excellent drainage such as a potting mix that is specially formulated for cacti.

New growth is a good sign that your cactus is bouncing back.

How to Remove Brown Spots on Cactus

Should I Cut Off Brown Spots on a Cactus?

It is not necessary to cut off the brown spots although it can be done if you prefer. Just remember that if you cut the brown spots off, they may never grow back.

If you can figure out the problem causing the brown spots on your cactus you can fix the issue and save your beloved plant from further damage. 

If the brown spots on your cactus are a real bother, you could start a new cutting of your plant by using an uninfected healthy area but be sure to use a sterile knife for cutting the plant.

This is important because the spores can easily transfer from plant to plant on the tools you use. Dust the cutting with sulfur to kill any spores that may have made their way over to the healthy section.

How to Avoid Brown Spots On Cactus

Most of the issues that cause brown spots to form on a cactus plant are preventable. With the proper care and conditions, you can prevent brown spots from forming on your plants.

Always make sure to not overwater the soil. After watering your cactus, check the soil for absorption and drainage issues. If the plant is sitting in excess moisture for long periods of time, this can become a breeding ground for a variety of different problems for your plant.

Observe how your plant reacts to the amount of sunlight it is exposed to and keep an eye on the temperature.

Don’t go overboard with fertilizer, only do this about once a year.

Watch for changes in your cactus and adjust accordingly.

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The Hobby Wife

The Hobby Wife

Greenhouse and backyard gardener, devoted homemaker, and passionate recipe creator. My journey through life revolves around my unwavering love for food and travel. As a passionate cook, I blend my garden's bounty with culinary finesse and inspiration from my travels. From farm-to-table homestyle dishes to copycat recipes that offer something unique, my kitchen is a canvas where flavors harmonize and ingredients tell stories.

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