Moon Cactus Dying | Facts On 3 Major Pest Problems And 8 Diseases |

Moon cactus dying is a common problem among many cactus gardeners. There are several reasons for this untimely death of the moon cactus.

In this article we are going to look into reasons, treatments and prevention methods of moon cactus dying.

Moon Cactus dying

Moon cactus pests


Mealybugs are tiny little creatures whom you would encounter commonly when growing moon cactus.

Mealy bugs could live longer  as well. These are tiny creatures, and you could spot them in gray or light brown in color.

If you have ever come across any white cottony substances, they could be mostly due to attacks of mealybugs.

They are so irritating as you could not even spot them at once to your naked eye. However it is important that you conduct daily inspections so that you could closely observe and identify  if there are any mealybug attacks.

Moreover, mealybugs could produce a sugary substance which could attract molds. It would be even worse since they could spread it to other plants as well.

Consequently, those cacti would be more prone towards fungal and bacterial invasions.

Mealybugs could create trouble for various parts of the cactus such as roots, stem, spines etc.

Their reproduction rate is also very high, and they tend to consume the juice these cacti generate. Chances are that the cactus could even  die if you do not treat them in advance.


It is important that you treat the mealybugs attacks well in advance as they could reproduce at a faster rate. 

To start off with, you could first isolate the cactus. After that, try using a pesticide spray to get rid of them completely.

Mealybugs have a cover which could act as a defensive cover from the pesticides. As such, best is to water them first and see whether  you could get rid of them physically.

Apart from that, you could consider using cotton buds dipped in alcohol to get rid of them as well.

When you use alcohol, they would help to dissolve the outer layer and could kill  them faster. When you finish doing that, you could spray pesticides as well.

Moreover, chances are that mealybugs could hide in the soil and damage roots as well. you could identify that if you spot any white fluff on the roots.

So, if you spot any, you could  wash the roots whilst using warm water. After that you could dip the roots in pesticide and repot the cactus.

When you plant them, ensure that the roots are dry. As a prevention method, you could use a systemic insecticide when they reach their growing season.

Mealybugs 1

Spider mites

Spider mites are yet another annoying creature which would make trouble for your cactus. Out of this, you would commonly spot red spider mites attacking the cactus.

They could also suck the juice of the plant. They would be red in color and small in size.

They could also stay alive in soil for so long and can reproduce rapidly. You could spot them forming tiny webs and that is a sign which they give out to indicate that they have invaded the cactus.

Further you could spot the cactus tend to take a dry look and turn brown. The mites absorb the juice from the cactus stem and due to that the color of the stem would change. 

They usually start invading the plant from the top and consume the fresh parts of the cactus. You could spot them as corking of the cactus.

As such best is to use a magnifying glass to observe them. Unfortunately, the brown parts of the bottom will remain there forever. Those red spider mites would be yellow, green or red in color.

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Spider mites are not fond of higher humidity areas and fresh air. So, you could  let the cactus gain fresh air all the time .

That will  avoid any potential invasion of the spider mites.  To start treating them, you could first of all, quarantine them. Use a magnifying glass and observe all the plants to identify them.

You need to adjust the treatment period depending on the season and on the severity of the infection as well.

For example, if you are treating them during summer, you need to do it for longer periods. You may use a pesticide to overcome the spider mites as well.

Avoid using insecticides . best is to use pesticides as they would be more productive to overcome the spider mites.

Spider mites 1

Fungus gnats

You could identify the fungus gnats as small black flies. On the other hand, their larvae would tend to look like little worms with blackheads.

Those blackheads would be around 4 mm long. Fungus larvae depend on organic matter in the soil and in cacti roots as well.

When the cactus is under the fungus attack, it would deteriorate the cactus’ healthy growth.


To treat this, the initial step you need to do is to cut down on watering  and let the cactus become dry.

You need to reduce  watering simply because they would love to stay in wet soil. If you think their attack is on a severe level, you could consider repotting them in a fresh soil mix which is well draining.

Avoid using manure or any other fertilizer which consists of high organic matter. Moreover, you could use sticky traps which could hang around your cactus.

In addition to that, you could try using an insecticide as well. Finally, be vigilant to not over water them also.

Fungus gnats 1

Moon cactus diseases

Moon cactus black spot 

You could spot the moon cactus forming black spots mainly due to extreme sunlight. Moon cactus are so responsive towards the light.

As such when you expose them to intense sunlight, they tend to form black spots.

Therefore , whenever you spot any black spots on the moon cactus, you need to immediately shift the plant somewhere where they get shade.

Moon cactus losing color 

Moon cactus would tend to lose their color due to bug attacks. It could be mainly nematode bugs and they are parasitic bugs.

They would make the moon cactus’ health deteriorate faster. Apart from that they would attribute the stem color to change as well. 

You could hardly spot these bugs and they would tend to stay in soil. Hence, you cannot identify them at once.

When your cactus is under these bugs attack,  your plant would lose the distinctive green color touch it has. 

To treat them, soak the roots in a jar filled with water.  Once you do that, you may see how those black dots leave the cactus.

Keep disinfecting the pot whilst applying boiled water and soap. Moreover, you could cut the damaged roots whilst using sterilized equipment such as shears or scissors. You may even repot them.

Moon cactus turning yellow 

Moon cactus would turn yellow due to nutrient deficiency. You could spot the yellowing of the cactus from the top part.

In addition to nutrient deficiency, your moon cactus would turn yellow due to viral and bacterial infections.

When you do not attend to the yellowing of the cactus at the beginning, it would cause rot and further deterioration of the plant. Fertilizing is the best solution which you could do to treat this.

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Moon cactus top rotting 

Moon cactus top rotting would first start from losing its colors and taking a wilted look of the cactus.

If you spot the scion is turning brown and look pale, you need to take that off.  Then it would be possible for the moon cactus to thrive without that part.

Further if you spot the moon cactus scion’s bottom part is discoloring, you need to immediately slice the part again and graft it in the rootstock. 

That would allow the cactus to thrive well.  On top of that keep in mind that moon cactus does not anyway live longer.

Moreover, when you water, make sure that you water them in a prayer instead of pouring water on the soil. Best is to spray water on them. 

Watering directly impacts the rotting of the plant. If you over water the cactus, excess water would not dry, and you could see how the lower scion rot, and this is what you could call top rotting. 

To further treat this, you could get rid of the rotted slices first and repot them whilst using a grafting method.

Moon Cactus dying

Moon cactus white spot 

White spots of moon cactus could be a result of scale attack. They usually depend on the cactus juice and usually tend to develop in colonies.

You could spot those in white coating. Those would look like mealybugs. They could also reproduce faster and tend to form white spots.

When the scales infect the moon cactus, you could see them leaving white spots and it would give a white fuzzy look for the whole plant.

It is important that you attend to this in advance unless they could reproduce faster and create more trouble. First you could quarantine the plant and start spraying water at a rapid rate.

Apart from that you could take them off whilst using tweezers also. Alternatively, you could use cotton buds and dip them in alcohol and apply them at infected places.

Keep doing this until you could eradicate them and to prevent them, you may use a systemic insecticide.

Moon cactus root rot 

Moon cactus are vulnerable for root rots and over watering is the main reason which could affect this condition. Further if you spot the lower part of the stem is soft, it is a sign of root rot.

To treat, you could trim the cuttings above the soft part of the cactus and repot them.

Once a moon cactus is suffering from root rot, it would lead the plant to die slowly. However, the most recommendable solution to treat this  would be repotting them in a fresh soil mix.

Make sure that you wash the roots first before you plant them again.

Mushy moon cactus

Over watering is what cause the cactus to turn mushy. You could mainly spot the rootstock of the cactus turning brown and becoming mushy.

To ascertain whether over watering has caused this, you could see whether the soil is wet and soggy even after you skip watering them for couple of days.

You could further check whether the roots are mushy and brown too. If they are so, you need to cut back on watering and check whether you have grown them in a well-draining soil mix.

Further make sure that you water them only after the soil medium is dry.

In addition to aforesaid, you could take cuttings and use them for the propagation process to make a new plant.

When you use the cuttings, ensure that they become callous first for a couple of days and then plant them. Within several weeks’ time, you could see how they form roots.

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You could have a fresh plant which is the same as the mother plant when you try this method.

Moon cactus stem turning brown 

If you spot your moon cactus stem turning brown, it is an indication of rotting.  If you take a healthy stem, it would be firm.

Further it will have a vivid green touch as well. Root rot is what causes the moon cactus to turn their stems  brown and root rot occurs due to over watering.

In addition to that, poor draining soil mix could also result in moon cactus turning brown.  If the roots have been destroyed on a greater level, it is very unlikely that you could save the cactus.

Apart from the aforesaid, bacterial infections and fungal infections could also result in moon cactus stems turning brown.

If the browning of the cactus has spread on a greater level , it is very unlikely that you could save the plant.

As such, what I would recommend is to dispose of the  cactus and try growing a fresh moon cactus.

To do that, you need to use a fresh soil mix and a clean pot, so that you will not come across such situations again.

moon cactus size 1 1

How to prevent moon cactus diseases and pests

I would urge you to use a mild balanced fertilizer particularly at the start of the growing season.

That would be beneficial to keep the cactus  healthy and to make it more  resistant towards pests and diseases.

Always keep the surrounding of the cactus  tidy and clean. If the surrounding area is unclean, those would be great breeding places for the invaders.

Do not leave the plant stranded in wet conditions for too long. Avoid over watering too.

You could use insecticides at the start of the growing season as that would also help them to distract the invaders from the cactus. Try using a natural pesticide as that would also help to get away from the pests.

Overwatered cactus

Avoid watering them for some days and let them dry.  watch out for mushy and soft parts of the cactus and remove  them.

Once the plant is dry, you could commence watering them and avoid over watering going forward.

How to save a dying cactus?

First and foremost, get rid of the rotting parts of the plant. Then check whether you need to change the pots which you have grown them in. 

If it is essential, you could use a sterilized pot and repot them. Make sure they get adequate sunlight.

You could ideally place the cactus in a bright sunny spot or alternatively shift to a sunny place during daytime for a few hours.

Be consistent in watering. If you spot your cacti seem to be dry and shriveled, you could commence watering them moderately.

When you water, always ensure that soil is dry. Ensure that you have grown them in a well-draining soil mix.

Further you could rinse off dirt and dust. You need to use an insecticide at the beginning of the growing season so that you could get away from any pest’s attack on the cactus. 


So here we are at the end of the article. You may now understand what are  the pests’ attacks and diseases that you will have to encounter when growing the Moon cactus and how to get rid of them.

They need a simple care treatment and a minor maintenance and they will grow healthily and reward you with  fabulous plants  in return.

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About author

I’m Dr. Chamika, As a hobby love talking about plants and showing you that taking care of indoor plants. My website is knowledge I’ve learned over the years and continue to learn about growing succulents. If you’re a succulent lover, then you have come to the correct place.