Why Does My Cactus Have White Stuff On It?

In a fast-paced modern world, succulents give busy homeowners the chance to raise houseplants for less. These low maintenance species require less care, less water and less precision than most other plant varieties. Whether cactus or bromeliad, a succulent is an attractive addition to a home that comes with minimal responsibility.

Yet, that doesn’t mean growing an indoor cactus won’t throw up a few surprises. like sudden white spots or web-like spots appearing on your cactus.

So why does your cactus have white stuff on it? The white stuff on your cactus is most likely a mealybug (cochineal insect) infestation. These little white bugs infest cacti plants to feed on the sap in their leaves. While they pose no risk to homes, they can decimate succulents causing stunted growth, deformed stems and yellowing leaves.

Mealybug on leaf figs. Plant insect infestation

If you’ve grown cacti before, you may already be familiar with their vulnerability to the mealybug (cochineal insect).

In this article, we explain why the mysterious white patches on your indoor cactus are most likely a mealybug infestation. We also discuss the best ways to eliminate mealybug infestations without causing harm to the plant.

Why Is There White Stuff On My Cactus Plant?

The frustrating thing about insect infestations is by the time you can see the problem, it’s probably quite advanced. It doesn’t mean your cactus can’t be saved. However, it almost certainly means the bugs have been there for much longer than you think.

Mealybugs are sneaky pests because they hide along the veins of leaves and at the leaf joints. It’s not uncommon for a person to go to bed with a healthy-looking houseplant and wake up to one covered in fuzzy white patches.

These white patches are often mistaken for mould growth because they have a slightly soft and almost wispy, cotton-like texture in some cases. In rare instances, the blemishes are caused by a fungus, but most are evidence of mealybug infestation. There is more chance of an indoor cactus being infested with mealybugs than fungus. However, you can perform a simple test to confirm this.

Using your finger or a gardening utensil, gently scrape a small amount of the white material from the cactus’s leaf or stem. Take care not to apply too much pressure and damage the plant. When squished, mealybugs produce bright red juice.

Here’s an interesting fact; cochineal insects are used in food production (yes, really) because this juice makes a very effective edible colourant. If you squish a white patch and see red, you’ve got a mealybug infestation that requires attention.

How Do Mealybug Infestations Affect Indoor Cacti?

The good news is your cactus plant can be saved. Though destructive, mealybugs are relatively slow workers compared to other pests like spider mites. If an infestation gets addressed quickly, the damage should be minimal.

If you ignore a mealybug infestation, the plant will eventually perish. Though this takes a long time and there’s plenty of opportunities to intervene. You’ll notice the plant develops yellow leaves, warped stems and irregularly shaped leaves.

The first step you need to take is quarantine. Put the affected cactus in a room away from other plants. Mealybugs aren’t picky and they will jump across to affect other species. After handling the plant, don’t forget to wash your hands and any gardening tools. Commonly, mealybugs are brought into a home on freshly grown fruits or vegetables, cuttings from outdoor plants and contaminated potting soil.

So, they’re surprisingly easy to bring home and cross-contamination between plants is possible. You don’t need to disinfect every surface and shut down the house; just be mindful of how you interact with a mealybug infested cactus.

How Long Does It Take for Mealybugs to Infest a Cactus?

The mealybug lifecycle lasts for a maximum of ten weeks. For the first week or two, the mealybug eggs develop into nymphs. For six to nine weeks after that, they mature into fully grown insects.

While their lifecycle is fairly short, it’s long enough to allow for multiple generations to exist at one time. It’s one of the reasons mealybug infestations seem to progress quite quickly.

As explained, it’s common to see nothing on an indoor cactus one day. Then, the next day, the plant is covered in fuzzy white patches. This happens because the individual insects are very small and tend to grow in hidden spots until an infestation is developed enough to spill out onto the plant’s leaves.

So, don’t feel bad if you didn’t notice it happening. The best thing you can do is take the right actions to eliminate the bugs.

What Are the Best Ways to Get Rid of Mealybugs?

Rubbing Alcohol

There are several ways to tackle mealybug infestations on cacti plants. One of the simplest is to dip a cotton swab in rubbing alcohol and gently touch it to any bugs you spot living on the stems and leaves.

It can be a time-consuming process, but it does kill the bugs immediately. For it to be effective though, the rubbing alcohol must directly touch individual bugs or clusters of bugs.

If you’ve got the patience to hunt down every mealybug you see on the cactus, this is an effective way to deal with the problem. You don’t have to apply treatment and wait.

The method works on contact. However, you must be thorough; check every visible area of the cactus. Look under leaves, around the leaf joints and at the base of the succulent. Remove the uppermost layer of soil around its stem and check for bugs there as well.

It’s less likely but it does happen, so make sure to check the very bottom of the plant pot for mealybugs. Check the sides also. Scrutinise all areas of the cactus plant and its container.

Repeat this process every day for a week making sure to kill any mealybug you spot with the rubbing alcohol. It may take a little while for the infestation to visibly subside. Be patient and keep tending to your plant.

Homemade Insecticide

A quicker method is to concoct a simple homemade insecticide. This is a pretty rough and tumble treatment. It will work, but it’s a harsh experience for your cactus plant. Dabbing mealybug clusters is tedious, but it is a gentle process compared with this method. It’s your choice though, so do what feels best for your succulent.

To create a mealybug killing solution, mix one teaspoon of mild liquid soap (such as Dr Bronner’s) with one litre of water. Like rubbing alcohol, this mixture should eliminate insects immediately.

What you can do here that you can’t do with alcohol is manually wash the cactus in a sink or shower. First, rub the plant with the homemade insecticide. Be as thorough as possible and check all of the places mentioned.

Then, when you’re convinced you’ve treated all affected areas, rinse the cactus plant with fresh cold water. Dry the cactus and return it to a clean, bug-free space. We recommend following up this treatment with two to three days of inspections. If you spot any stray mealybugs, use the rubbing alcohol method to dispatch them.

The rough rinse should deal with almost all of the pesky insects, but you will probably find some individual bugs hiding in seams and joints. This is why it’s important to follow up the rinse with daily inspections. Keep treating the plant until you’re confident all evidence of the mealybug infestation is gone.

Will the Mealybugs Ever Come Back to My Cactus?

Consider the fact much of a mealybug infestation is not easily visible. It means eliminating these insects takes time. You may need to repeat your chosen treatment several times over the course of weeks or even months. While mealybugs are easy to kill individually, their numbers mean they present a frustrating problem for homeowners.

Yes, the process can be tiresome. What you need to ask yourself is whether your succulent is worth the work. For most, it’s a small price to pay to save a cactus. If you’re not willing to treat the infestation properly, the best move is to get rid of the cactus as soon as possible. Wrap it tightly in plastic and throw it out so the mealybugs won’t pass to your other houseplants. Always check nearby plants for evidence of infestation.

Our advice is to keep an affected cactus in quarantine for three weeks. If there are no further signs of infestation after this time, it’s probably safe to bring the plant back to its original location and neighbours. Before you do this, it’s worth giving the spot a quick inspection to make sure there’s nothing in the area to cause a new problem.

What Can I Do to Beat Recurring Mealybug Infestations?

If infestations keep occurring, you haven’t dealt with a hidden source. Until you identify and eliminate this source, the problem will continue. There are a few actions you can take to increase your chances of success.

For instance, if infestations are reoccurring on the same cactus, try removing the top inch of soil from its pot. Replace with fresh soil. Again, remember to wash your hands afterwards.

Use a cotton swab dipped in rubbing alcohol to treat the inside rim of the plant pot and kill mealybugs hiding there. You should also relocate the affected plant.

Carry out the bug treatment as described but do not return the cactus to its original location. There may be something in the area helping the bugs to flourish. Commonly, eggs are dropped around a cactus’ location. As they’re so hard to see, they’re easy to miss.

The Final Word on Dealing with Mealybug Infestations

If you follow these steps and have patience with the process, it will eliminate all of the mealybugs on your cactus plant. Unfortunately, due to their varied sources, there’s no guaranteed way to prevent the insects from ever entering your home.

However, with a little vigilance and care, it’s possible to stop infestations as soon as you spot them.