What Are the White Spots on My Cactus?

Not everyone has a green thumb. Most people start with a small potted plant to see how long it can survive under their care.

In today’s fast-paced world, the best way to find out whether you are a plant person or not is to get succulents. They tend to be pretty low maintenance, and they will adjust right into your busy work hours.

Some of the top benefits of succulents include:

  • Their colors brighten your home
  • They purify the air
  • They improve humidity in the home
  • They improve your focus
  • They enhance memory
  • They increase pain tolerance

If you don’t have any room in your schedule for another responsibility, you will love succulents.

The question that now remains is what type of succulent should you get? Well, we have got one in mind.

It’s the star of cowboy movies, the one plant that survives the desert. It’s edible, prickly on the outside, and meaty on the inside.

We are talking about the resilient cactus.

Cactus is hassle-free. It does not require much care, food, and water compared to other houseplants.

However, they do have a couple of issues that become prominent slowly.

These issues don’t occur because of neglect on your part; it’s simply how the plant behaves when exposed to the environment.

If you see white spots on your cactus, take action immediately. There are various reasons behind this, and if you don’t find a solution soon, they can cause deformed foliage, yellowing, and stunted growth.

The Causes Behind a White Cactus

The most common cause of white spots on cactus plants is a Mealybugs infestation. Next, you need to eliminate fungus, a possible cause for these spots.

Fungal growth can cover the plant with a powdery mold. It forms as a result of the necrotic spot virus.

Even though a cactus does not require any support to grow, it does need the occasional sun and water.

Now that you know the basics of having a cactus, let’s take an in-depth look at the causes of white spots on it:

High Sun Exposure

Cactus loves the sun. Hence, it can survive in the desert.

One would assume then that a little sunlight won’t hurt it. It doesn’t, but when this sunlight falls on it directly, it starts to look a little crispy and white.

This sunburn is caused by UV radiation, destroying the living cells on the outside.

As a result, the cactus becomes dehydrated, and the water evaporates from its spines, needles, and leaves.

Treating Sunburn

If you have placed your cactus on the windowsill, we suggest you change its location.

Move it to a shaded location and make a habit of spraying it with water every day until it regains its color, and the skin no longer looks dull.

You can then reduce the application of water to twice a week to keep it cool. Refrain from applying fertilizers because it will increase the severity of sunburn.

Cold Temperatures

Cactus cannot withstand cold temperatures. If the temperature in your area drops below 50F, your cactus will turn white.

The change will start with ice crystals forming on the skin, which will cause it to become squishy.

This condition is temporary, and the plant recovers in sunlight. However, if the temperature is too high and the exposure too long, your cactus will die.

Treating Frost Damage

Bring your cactus indoors and keep it somewhere warm. That’s the best you can do to revive it. Give the cactus plenty of water to nurse it back to health.

Prune the cactus’s dead branches and place the cactus on your windowsill when the sun shines bright outside.

Recovery from frost damage is slow because it affects the cactus from the inside. Give it a few weeks, and your cactus will be all prickly again.

There are a few precautions you can take to protect your cactus from frost damage:

  • Place your plant indoors as soon as the temperature drops too low and too fast
  • Make sure the soil does not go dry (Check the pot from underneath and inspect for any drainage holes. If you see a crack, transfer your cactus to another pot)
  • Cover the exposed roots of your cactus with mulch or insulating material, such as straw bales or leaves
  • As the day becomes colder, cover your cactus with burlap to prevent it from drying out


Yes, there’s something such as overfeeding your cactus. When your plant is given too much fertilizer, it starts to turn yellow because it is getting too many nutrients.

As a result, the level of chlorophyll drops, which causes the branches to die. Sometimes, too much fertilizer shows the same signs as sunburn.

This happens because the fertilizer stops the plant from absorbing sunlight for photosynthesis.

Treating Overfeeding

First of all, you should give your cactus fertilizer once a year. Prune your cactus regularly. If you want your cactus to grow tall, refrain from trimming it from the top.

Instead of using fertilizer, use a cactus soil mix to keep the plant from becoming yellow.

Not Enough or Too Much Water

Yes, you can over-water or under-water your cactus. As we said earlier, succulents don’t require much water. The effects of both actions are different.

  • Overwatering: The cactus will start to wilt due to too much moisture. The white spots will appear next, leaving a slimy coating on the skin.
  • Underwatering: The cactus will start to wilt and make the spines turn white.

After a while, the cactus will start drooping and look yellow, eventually drying out.

Treating Underwatering and Overwatering

If you have overwatered your cactus, the most obvious solution is to place it out in the sun to dry out. Make sure the plant is not under direct sunlight; otherwise, the plant will become crispy.

When the cactus is underwatered, you must re-water the roots until the water flows freely. Wait for a while and let the excess water drain. Water the cactus again and repeat until the cactus looks healthy.


A cactus plant placed indoors is vulnerable to insects such as scales and Mealybugs. The white spots you see on your cactus are not constantly molding.

They can also be a shield created by the pests to hide them. Scales are insects covered in white fuzz that feed on the cactus sap. As a result, the plant develops white or yellow spots.

Mealybugs, on the other hand, Mealybugs are 0.5 cm long and feed on the cactus skin. They have a growth cycle that lasts for ten weeks.

The eggs develop into nymphs in 2 weeks. After the sixth week, the nymphs mature and turn into adult bugs; this is why Mealybugs spread so fast. As they feed, they multiply and cause more havoc.

Treating White Spots Caused by Pests

It usually happens that you spot the damage too late. Start by placing the cactus in quarantine. Make sure your cactus is not placed beside other potted plants.

Mealybugs like to eat so they will feed on any plant. As a precaution, spray all your other plants with a diluted Neem oil and water solution.

You can do two things to kill the Mealybugs: repot your cactus or use tweezers to remove them. These methods might or might not work. If you don’t see any positive results, here’s what you can do:

Use Isopropyl Alcohol

  • Soak a cotton ball in alcohol and gently dab it on the white spots. It will take time to cover all the spots, but the solution will destroy the insects immediately.
  • Mealybugs like to hide deep in the crevices of the cactus. So, inspect the plant’s base, leaf joints, and undersides.
  • If you spot white spots on the roots, use lukewarm water to wash them and apply some pesticide. Once the roots have dried, repot the cactus.

Apply isopropyl alcohol on your cactus for at least one week. Do not skip a day in between because this will cause the Mealybugs to multiply.

Test the alcohol on a small part of the cactus leaf in a small amount to prevent burn.


The area where fungus grows usually turns soft. This happens when your plant is placed in wet or humid conditions.

While white spots don’t harm your plant much, they cause yellowing and stunted growth.

The powdery mildew deforms the leaves and causes the plant to decay from the inside. Depending on the cactus species, the spots’ color might differ.

Treating White Spots Caused by Fungus

Remove the areas of the plant that are infected. Make a solution with 3 parts water and 1 part milk. Pour it into a spray bottle and apply it to the moldy leaves.

Use this solution for three days straight and then repeat after 14 days.

Final Thoughts

White spots on cacti are quite common and usually occur due to neglect. The cactus plant does not need much water, sunlight, or food.

However, you still need to pay a little attention to its care to ensure it does not turn yellow or rot.