White Powder On Cactus? How To Remove Mealybugs in 6 Simple Ways

Have you noticed some white powdery substance hiding on the crevices of your cactus stems? Did your cactus experience growth deformation and discoloration? Inspect your plant right away as it may be infested with mealybugs!

Mealybugs are white, fuzzy insects, 2-3mm long with filaments around their body. A mealybug infestation looks like a cottony mass often found on the discreet part of the plant. This insect can be quite harmful if left unchecked, but they can be removed in 6 different ways:

  1. Alcohol application,
  2. Blast off with water,
  3. Drench with soap solution,
  4. Submerge in a neem oil solution,
  5. Use of beneficial insects, and
  6. Use mild contact insecticides.

Mealybugs are inconspicuous unless you purposely inspect your cactus. If you are keen on the signs of infestations, you can rule them out.

I will be sharing with you the practical ways I used to eliminate mealybugs over the years. But first, let’s get to know what mealybugs are.

Steps To Rule Out Mealybugs – Infographic

How to Identify Mealybugs on Cacti? The 2 Signs

The mealybug problem on cacti appears like elliptical white bumps with fibrils or large clusters of white substance. It is essential to identify the infestation to avoid confusion with cacti areoles.

The photo shows the difference between a mealybug and a cactus areole to avoid confusion.

1- Small elliptical white bumps with fibrils. The early infestation starts with one or more adult female mealybugs settling to feed on the folds and crannies of the cactus. You can identify mealybugs from the filaments around the edge of their bodies.

2- Large clumps of foamy white mass with yellow spots- When the female adults start to settle and feed, they excrete a sticky liquid called honeydew. Soon after, they will form a white sac where they lay their yellow eggs to hatch, and colonies begin to develop.

6 Simple Ways To Rule Out Mealybugs Like A Pro

Mealybugs are so good at hiding that the insects can hardly be seen if a grower doesn’t look closely at the cactus. Often mealybugs are identified only when it is too late, and the plant is totally infested.

So, how can you eliminate mealybugs? Let me take you to the processes I did with my cacti to tackle mealybugs infestation.

1- Alcohol Application

Alcohol is an impressive weapon against mealybugs. The chemical composition of alcohol destroys the wax covering of the mealybugs and kills them.

Since mealybugs are soft-bodied, the application of alcohol will significantly affect their activity. A 50-70% alcohol solution can penetrate their waxy coating upon contact and knock them dead. You can dab a q-tip on an individual bug or spray generously on the dense cluster break them off.

Alcohol is proven safe for cactus as long as the application is made away from direct sunlight. You may have to re-apply quite a several times to ensure all mealybugs are killed. Using this method alone on severe and heavy infestation is not recommended.

NOTE: Infected cactus with closely packed spines will not significantly benefit from this remedy. It would be difficult to reach the inside part with a q-tip due to the dense spines. The water blasting method is the best approach in this case.

2- Blast Off With Water

Blasting off a heavily infested cactus with a slightly pressured water spray will whack off adult and young mealybugs alike, or even eggs.

With a pressurized water spray, blast mealybug colonies and egg sac hiding on undersides. It will dislodge off the cactus-sucking mealybugs, including their eggs. Remember to do this away from other plants, as mealybugs can be transported due to the pressure.

Tip: It is best to uproot your cactus when doing a water blast approach to eliminate insects hiding beneath the roots. Blast the root system removing all the soil, and wash your cactus thoroughly. Let the plant dry first before reporting to a new pot and fresh medium. Sturdy cactus infested with mealybugs favors this approach.

3- Drench With Soap Solution

Oil-based insecticidal soap mixed with a portion of water is another helpful way to break down mealybug’s fuzzy covering. This method is not only proven safe but eco-friendly as it is less destructive to beneficial insects.

An effective soap solution again mealybugs is obtained by mixing:

  1. 2tsp organic insecticidal soap in
  2. a gallon of water.

Spray the solution directly and generously drench the mealybugs to make contact and weaken their waxy coat.

You may pour soap solutions on the potting medium to kill mealybugs hiding on the root. Insecticidal soap has no residual effect, so it does not have a lasting impact on the bugs.

Re-application after a couple of days would be best. Always test for phytotoxicity before application, as some cacti are sensitive to chemicals. I usually spray at dusk to avoid sun damage.

An insecticidal soap with a high percentage of potassium salt fatty acid like the one below from Amazon is an excellent mealybug buster.

4- Submerge In Neem Oil Solution

Azadirachtin is the active component of neem oil that acts as a natural insecticide, and so it is very effective against mealybugs. The residual effect of neem oil will last for a week, so it has a much longer impact on mealybugs.

Make a neem oil solution according to the recommended mix ratio found on the product label. Usually, the proportion is an ounce of concentrated neem oil to a gallon of water. You may either spray directly to the infestation or submerge the whole pot in a tub of neem solution for 1 minute.

Plunging the whole plant will allow the solution to penetrate through the roots and contact every single mealybug present. After a few seconds, dead brown mealybugs will begin rising above the neem solution.

As a rule of thumb, perform any treatment during sundown to avoid burning and for the solution to have the chance to dry out overnight before beneficial insects become active in the morning. You may re-apply after a week or every 3 weeks for prevention.

Below is excellent neem oil.

5- Use Beneficial Insects

Beneficial insects can help oust mealybugs in an outdoor or sunroom setup. Invite ladybugs, lacewings, and parasitic wasps to swarm in the garden to help deal with the infestation.

If you are growing cactus outdoors, they will benefit from the presence of beneficial insects that feed on mealybugs. These predators can help lower the population of mealybugs. Inviting these insects to work in your garden will save you from spending money on insecticides.

However, this biological control method is not viable for indoor arrangements unless you want ladybugs inside your home.

6- Use Mild Contact Insecticide Solution

Spraying contact insecticides can cause paralysis in mealybugs. These insecticides are used in an advanced stage of infestations.

Many broad-spectrum insecticides effectively kill mealybugs, but I only recommend using them in extreme situations. Gardeners should minimize their use if possible or in mild concentrations only due to potential adverse impacts on pollinators and other beneficial insects.

I only use contact chemicals (containing Permethrin) if the mealybugs are getting out of hand, like when more than 50% of the plant is heavily infested, which happens rarely. Bear in mind that none of these insecticides can eliminate mealybugs totally, and you will need to treat them again if needed.

In most situations, enhancing proper gardening practice and biological control will help suppress the spread of mealybugs.

What Damage Do Mealybugs Cause On The Cactus?

Fewer infestations of mealybugs cannot harm a cactus. But as they multiply and form colonies, they can cause harmful damage that is lethal to the cactus, such as deformation, stunted growth, root rot, and discoloration.

A large group of mealybugs feeding on the sap of the cactus can reduce plant vigor. As they feed on the cactus, they inject toxic saliva into its stems, causing deformation and stunted growth.

They also excrete honeydews while they continue feeding. Honeydews are the breeding site of sooty molds that covers the stem of the cactus. The black sooty molds prevent the sunlight from getting into the plant stem, making the cactus impossible to perform photosynthesis. Therefore, discoloration or chlorosis is likely to occur.

Mealybugs that feed on the roots of the cactus leave honeydew, which develops into mold over time. Heavy infestation means more honeydew and an increased mold population. Eventually, the roots will rot, and the cactus will die.

Early infestation may not cause a significant problem on the cactus. However, mealybugs’ ability to reproduce exponentially fast indicates that heavy infestation will happen in no time.

What Are Mealybugs?

Mealybugs are tropical insects from the family of Pseudococcidae that feed on many plants in the greenhouse, outdoor gardens, and indoor settings. They form in clusters or colonies, piercing through the plant’s stems and roots and sucking on their juices.

Magnified view of an early infestation where mealybugs begin to settle on a cactus pad

These destructive insects are called mealybugs due to the ashy substance that envelopes their body. Unlike armored scales, they have a fluffy waxy coating that serves as their defense mechanism towards potential predators, harsh pesticides, and elements.

Mealybugs excrete sticky honeydew as the by-product of feeding. Honeydews coat infested parts and are an excellent breeding ground for fungi such as black sooty molds. They can be unsightly and harmful in large quantities, and attract ants into the cactus.

Appearance

Mealybugs are grayish-pink and soft-bodied crawlers that measure around 2-3 millimeters long. These insects are somewhat elongated, with distinctly segmented bodies covered with white waxy materials.

Adult female mealybugs usually have filaments around their body edges which appear like tiny legs. Some species have waxy fibrils projecting from their rear end that is generally used to distinguish between other species.

They like the spots in between the cactus ribs or at the base of the spines. When they form clusters, they appear to be cottony bumps which is why mealybugs are confused as wooly areoles of the cactus and often disregarded.

Lifecycle

Some mealybugs lay hundreds of tiny yellow eggs in a cottony sac, while other species bear live offspring. Depending on temperatures and species, mealybugs may have three to six generations.

After mating, the female mealybug lays almost 600 eggs inside a dense, cottony substance called ovisac or egg sac. At higher temperatures, egg-laying will be fewer. Tiny nymph crawlers are hatched and begin to creep out from the egg sac within 7 days.

This is crazy! Female mealybugs can reproduce without mating. This means that only one female can create a colony of mealybugs by cloning herself!

According to the University of Wisconsin, female mealybugs die after 5-10 days of laying eggs or offspring. Within two to three months, another generation of adult mealybugs is ready to begin the cycle until they form a colony. Female adults are oval and can move around slowly.

Male mealybugs are smaller than females and have a pair of wings that look like gnats.

The female nymph mealybug does not lose their legs as they mature and remain mobile throughout their lives. They appear flat, yellow to orange, and do not produce wax until they settle and begin feeding.

Identification

Mealybug species are distinguished by the presence of fuzzy filaments surrounding their body margins. There are species with short fibrils on the sides but longer on the rear. Some have uniform filaments around, while others have none.

In the United States, there are around 275 mealybug species known to exist. Here are the three major species that attack cacti and other succulent plants.

SPECIESDESCRIPTION
Long-tailed Mealybugs  ‘Pseudococcus longispinus’– Mature females have white anal filaments, 2 are longer than their body, and the other 2 are shorter.- They don’t lay egg masses but instead give birth to live nymphs. 
Citrus mealybug
‘Planococcus citri’
– This species has a uniform, short, slightly curved filament around its body, and sometimes a dark stripe lining is visible down its back.
– Females lay hundreds of eggs in a thick, fluffy mass egg sac. 
Root mealybugs‘Rhizoecus pritchardi’– They do not have apparent filament around their body. 
– Live on the soil and mainly feed on the roots.- Lays egg in a nest-like setup.

How To Avoid Mealybugs From Spreading?

No matter how good and expert a gardener is, plants are still susceptible to pests and insects. However, wise management and practice in the garden can help avoid mealybugs from staying and spreading out.

I have been dealing with mealybugs for several years, and I must say, they are inevitable. One moment they’re gone, and the next time you know they’re on your plants again.

Here are the practical ways to avoid the spread of mealybugs:

  • Always isolate newly purchased plants. Quarantine and observe your new plants for several weeks before mixing them with other existing plants.
  • Wash and repot new plants. I strongly encourage this practice, although it may seem tiresome and requires a lot of work (well, that’s gardening in the first place). It is better to do it at once than repeatedly treat your cactus due to infestation. Well, that’s more exhausting.
  • Be vigilant and inspect plants frequently. Regular plant monitoring is a wise move to intercept the presence of mealybugs earlier while they are still manageable before they begin infesting neighboring plants. I do this while watering, so it does not take extra time. You will also notice any unusual harmful changes in the condition of your cactus and act on it sooner.
  • Maintain cleanliness around the area. Mealybugs are attracted to the moist surface. Keep your plant racks dry and clean to avoid pests and unwanted insects from breeding. Throw away rotting materials as they make an ideal habitat for pests.
  • Isolate right away infested cactus. If you discover an infestation, separate the diseased plant and apply appropriate treatment as soon as possible. Examine other nearby plants for a possible invasion.
  • Avoid overwatering and overfeeding your cactus. These parasites enjoy the mushy, overwatered stems of the cactus, and they love feeding on plants with high nitrogen content.

How Do Mealybugs Get Onto Cactus? 5 Reasons

Newbie gardeners often wonder why their cactus get infested with mealybugs. They don’t notice their cactus is invaded with bugs until the damage is apparent and far advanced.

The 6 Reasons why mealybugs get on cacti are:

1- Birds, insects, and predators are possible carriers of mealybugs.

2- Mealybugs on the infested plant (perhaps newly acquired) can crawl on nearby plants.

3- Using old potting soil and dirty pots that may have been infested with mealybugs.

4- Keeping your plant moist for a longer period invites mealybugs.

5- Winds can transport the tiny nymphs to another plant.

Mealybugs are prevalent in moist and humid settings. They are favored by warm climates and attracted to the plant’s soft tissues.

Cacti are mealybug’s favorite because of their succulent stems and soft tissues. The soft tissues provide easy access for mealybugs to suck on the sap of their stems. Overwatered and overfertilized cacti have a higher chance of getting mealybugs.

Takeaways

  • Mealybugs can be removed by applying alcohol solution and blasting off with water. A heavily infested plant can be drenched with soap solution or mild systemic insecticide to kill mealybugs instantly. However, inviting beneficial insects to deal with mealybugs is the safest and economical method.
  • While a small infestation cannot affect the plant’s health, the extensive invasion of mealybugs can cause a cactus to deform, discolor, stunted growth, and root rot.
  • Frequent monitoring of your plant is one way to prevent the spread of mealybugs in your collection.

Sources

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