Ultimate Guide: How To Fight Cactus Diseases And Pests

Fighting Cactus diseases and pests is one of the challenges faced by gardeners who grow cacti and succulent plants. This comprehensive guide – The Ultimate Guide – features detailed information on identifying and treating plant diseases and common pests that cause problems.
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Cacti are unique plants known for their drought and diseases resistance. However, this doesn’t mean these hardy succulents are immune to pests and diseases. While some cacti pests and diseases are a result of human neglect, others are natural and inevitable. As with all plants, cacti are vulnerable to insects and diseases. This is especially true if you live in a region with high humidity or have often watered houseplants. We look at the most common cactus diseases and pests and provide some natural and artificial remedies to get rid of them and keep your cactus healthy.

So how do you deal with cactus pests and diseases? For most cactus diseases like powdery mildew, mealybugs, and scale insects, simple houseplants remedies like neem oil, insecticidal soap and a good strong jet of water will do. For pests like red spider mites and aphids, insecticidal soap works well as a pesticide. For diseases like brown rot, take away the infected plant parts and sanitize your cacti with a mixture of hydrogen peroxide diluted in water. More serious problems like brown spot fungus or bacterial infections like bacterial spots will need to take more drastic measures like cutting off the diseased parts of the cactus plant.

Are you worried about cactus pests and diseases? This article should help you identify and treat common cactus diseases, pests and infestations.

Common Factors That Lead To Cactus Pests And Diseases

These causes can be classified into two main groups:

  1. Human neglect
  2. Natural factors

Human Neglect

Humans are often to blame for cactus pests and diseases. Some of the common human activities that lead to this include:

Overwatering This is by far the most common cause of cactus disease. Cacti are desert plants, so they are very vulnerable to overwatering. Since their roots don’t store water like other plants, this often leads to root rot and fungal infections that can be fatal for your plant.

Underwatering – On the other hand, cacti are also vulnerable to underwatering. Cactus may be desert plants, but they still need water. If you suddenly stop watering your cactus, it will start dying slowly from the roots upwards.

Overwatering and underwatering are two of the most common causes of pests and diseases in cacti.

Using non-organic fertilizers – These can be another common cause of cacti diseases and pests. Fertilizer that contains heavy metals like copper or zinc is especially harmful to all plants (including cacti). Using inorganic fertilizers can eventually damage your cactus and make it more susceptible to diseases.

Overfeeding – This happens when you give your cacti too much water or fertilizer. This is often the result of overwatering, which leads to root rot and fungal infections that damage your plant’s roots

Physical injury – Cacti are prone to physical injuries because they have no protective bark or leaves. A bump can lead to infection, making them more vulnerable to pests and diseases

Natural factors

These include weather changes, soil composition, humidity levels in the air etc. Some of these natural factors are:

Temperature – Temperature fluctuations often cause stress to cacti because they originate from different geographical locations. An example is when you move your desert cactus indoors during winter seasons where temperature can drop below freezing point.

Humidity – This is another natural factor that affects cacti differently depending on the type of cactus you have. Humid climates can help certain types of cactus grow faster, while most desert plants prefer a dry environment instead to prevent fungal infections and other pests and diseases

Soil composition – The composition of the soil also affects cacti. For example, a lot of sand can hinder their ability to absorb water and nutrients from the ground. The mix of sand and other materials in your cactus soil should be carefully considered before planting.

Improper soil composition often leads to pests and diseases in cacti.

Cactus Diseases

Cactus Rot


Cactus rot comes in two common forms; root rot and stem rot. Root rot comes about when you overwater your cactus or do not allow it to dry out between waterings. Most of the time, the rot will begin in the root system and spread upwards towards the rest of the plant. This is why it’s really important that you let your cactus completely dry out before watering again. Stem rot, on the other hand, can either be a result of  bacteria or fungi. If it’s bacterial, you will notice a dark liquid ooze from the stem of your cactus. This isn’t good and needs quick treatment before you lose the entire plant. Fungal rot can also cause stems to swell up and become mushy like rotten fruit, but more often than not, it will appear as if the stem is bruising.

Root rot is typically a result of overwatering a cactus.


Symptoms of fungal rot include dark, sunken spots on the stem, which will turn into mushy areas. If it is bacterial, there may be a black liquid oozing from any part of your cactus; this should not be ignored and needs treatment right away before you lose the entire plant.


Cure the cactus disease by immediately removing any affected parts of your plant and treating it with fungicide or hydrogen peroxide. If fungal spores cause rot, you can also treat it with commercial anti-fungal sprays available at most garden stores. Mist your plants frequently to keep humidity up around them. This will help take care of both fungal and bacterial rot.

Cactus Rot Prevention

Make sure to keep the soil around your plants moist but not wet and misty them frequently – this will help prevent bacteria from forming on the plant. Always make sure there is plenty of ventilation in any enclosed place you may have a potted cactus in. It doesn’t matter whether that is in a greenhouse or inside your home.

Yellowing of a cactus


The yellowing of a cactus is a result of improper watering and fertilizing and allowing dust to build up on the plant. Some of the most common causes include over-watering, insufficient sunlight, incorrect soil for your cactus, and too much fertilizer (especially nitrogen).

If you keep giving water to the cactus that does not need it, the roots can rot. This leads to root-bound plants and eventually yellowing leaves as well.

If your cactus is turning yellow, you may have been watering and fertilizing the plant incorrectly.


Yellow or white spots on your plant will be a sign of over-fertilizing. Other symptoms you should look for include shriveled-up leaves. This means too little water is available to the plant, resulting from too much sun exposure.


Cactus that require more water should immediately have their soil watered thoroughly until it begins seeping out from the bottom. They will also need a good amount of sunlight, so try moving them closer to a window. If your cactus is looking dry and not thriving, it may be time to give them some more fertilizer or water with plant food specifically made for cacti.

Cure yellowing of a cactus by giving the roots plenty of room to breathe. Ensure they get enough sunlight and ventilation so that their leaves can absorb enough water; and by feeding them with a cactus fertilizer.

Sunburnt Cactus


Cacti exposed to direct sunlight can be at risk of getting sunburnt. This is especially true if they are in a location where there is very little shade.

Cacti may get sunburnt when exposed to excess direct sunlight.


If you look at your cactus and notice that it’s losing its green color, this could result from sun damage to the leaves. The same goes for any brown spots appearing on its skin. Withered leaves may also accompany these.


Move your cactus to a location with more shade and mist the plant frequently. This may help keep it hydrated. If you want to give them some water rich in nutrients, try using cactus fertilizer on the soil surrounding the roots of your sunburnt cacti.

Frost damaged cactus


If your cactus has been exposed to frost, it could kill the plant. Other causes of damage include extremely hot conditions or severe drought. Frost damage is often found on the cactus flowers, stems, or leaves; white coloration can easily identify.

If your cactus is exposed to extremely cold temperature, it may gradually die.


If your plant has been exposed to freezing conditions or extreme temperatures that are either too hot or cold, you may see dry spots appearing in various areas of its body. The same goes for brown or yellow spots or patches.


You can help protect your cactus from frost damage by overwatering them during the winter months. This will prevent any potential freezing conditions that might happen when water freezes in cracks on their skin. It would help if you also tried to give plants with flowers some extra space between other plants, as frost can damage the cacti flowers.

Where possible, you should immediately move them to a location with warmer temperatures and try giving them some more sunlight. This will help speed up the healing process by encouraging new growth after frost exposure.

Cactus Pests

Red spider mites

Red spider mites are common pests that affect cacti. They are small parasites that can cause significant damage to your plant by weakening its tissues, which will eventually lead to yellowing leaves or shriveled growths.

How to Identify

If you notice brown speckled spots on the surface of a cactus or spider webs near these areas, it is a sign of red spider mites. Be aware that these parasites can reproduce quickly, so they must treat your plant as soon as you notice the aforementioned symptoms.

How it Affects Cacti

These pests suck out fluids from your plant’s tissues, which is how they cause damage and weaken its growth. Since their webbing can also trap dust and dirt, these parasites may prevent a cactus from receiving the water it needs.


Spray your plant with an insecticide spray that is specifically made for red spider mites so you can kill off any existing infestations on your cacti. You should then monitor the plant for a few weeks to ensure that all pest eggs have been destroyed.

Fungus gnats

A fungus gnat is one of the most common pests that affect cacti. This is because the pest loves moist conditions and decaying matter. These small flies will reproduce quickly in damp environments, so any rotting material or dead leaves on your cacti may attract them.

How to Identify

Look for small black insects that resemble mosquitoes hovering around the base of a plant (or in its soil). These are fungus gnats, and they will lay their eggs close to decaying matter, so they have enough food when they hatch. If you notice many tiny larvae crawling around the cactus, then this is also a sign of fungus gnats.

How it Affects Cacti

These parasites can cause damage to your plant by feeding on its roots or stems. They may even feed on any eggs that are present on its surface. Since fungus gnats reproduce quickly in moist conditions, these pests could spread to other plants if the infestation remains uncontrolled.


You can prevent fungus gnats from causing damage to your cacti’s roots and stems by allowing them proper drainage, so they don’t stay moist for too long. It would help if you avoided overwatering, as this could result in fungus gnats hatching and causing damage to your plant.

Snails & Slugs

Slugs and snails will feed on cacti leaves, leaving behind holes that look similar to those made by beetles or caterpillars. If you spot any snail/slug trails across the surface of a cactus, there is a chance that these pests are eating from it.

Snails may feed on cacti leaves and make the plant even more vulnerable to other parasites.

How to Identify

These parasites will leave tell-tale mucus trails on the surface of your plant, as well as damage that looks similar to those left behind by beetles or caterpillars chewing away at leaves and stems.

How it Affects Cacti

The holes created by slugs/snails can leave your plant vulnerable to other parasites, so they should be dealt with immediately if you spot them on a cactus. You will also need to keep an eye out for any eggs present in the soil surrounding your plants, so their population does not spread.


To prevent slugs and snails from causing damage to your cacti leaves, try trapping them in beer traps or secure copper bands around the base of a plant (or any other containers). While this will not kill these parasites off completely, it should help reduce their population if you notice them hatching on your cacti.

Root mealybugs

These pests are usually only found near the base of a cactus, where they feed off its roots and stems (which can cause serious damage to their health). You may spot white cotton-like patches growing around this region if root mealybugs have taken hold of your plant.

How to Identify

When you notice white cotton-like patches growing on the roots of a cactus, root mealybugs are likely to be present. These parasites also have whitish/yellow bodies covered by waxy filaments (which can be confusing if you’re not sure what they look like).

How it Affects Cacti

Root mealybugs feed on the roots and stems of a plant, which can cause serious damage to its health. You may also notice stunted growth or wilting leaves if their population becomes large enough.


To get rid of root mealybugs, you should remove the affected soil from around a cactus and replace it with new, fresh soil. If the infestation is small, you can also try mixing up some sugary water (using sugar or honey) that will attract mealybugs away from your plant.


These pests are usually found chewing on cacti leaves, where they will leave behind tell-tale holes in the plant’s surface. If you notice these parasites crawling on a cactus, they have likely been eating from its leaves and stems.

How to Identify

Beetles are usually brown or black, with hard outer shells protecting their bodies. They also have hard chewing mouthparts that are perfect for pruning cactus leaves and stems.

How it Affects Cacti

Beetles cause damage to a plant by feeding on its leaves and stems. This can lead to stunted growth if left untreated. You may also notice leaf loss or wilting in the case of, particularly bad infestations.


You can kill off beetles by placing sticky traps around a cactus (or removing them manually if they are in reach). You could also try mixing up some sugary water that will attract these pests away from your plant. However, it is important to remove any dead leaves or stems where the beetles have been feeding from, as this is where they tend to lay their eggs.


You will likely find these parasites on the stem of a cactus, where they attach themselves and feed off its sap.

How to Identify

Due to their small size, scales can be difficult to spot on a cactus. You will notice that they have tiny brownish spots covering the surface of their bodies, which may appear white if you look closely enough.

How it Affects Cacti

Scales feed off the sap in a plant’s stem and leaves, causing them to become stunted in appearance. If left untreated, this can result in cactus death (with their sap-sucking mouths making it impossible for new shoots to grow).


You should remove any dead leaves or stems around your plant if you notice scales feeding on them. You could also try mixing up some sugary water that will attract these parasites away from your plant. However, the most effective way to get rid of scales is by applying a sticky substance (like petroleum jelly) on top of the stem so they can no longer feed off its sap.


Cactus are beautiful plants that help add some ambiance to your home. However, this can only be possible if you do your part to help keep them from the effects of pests and diseases. In case you are in doubt about some signs and symptoms, always consult a professional arborist. With constant monitoring and proper care, you should be able to maintain a healthy cactus garden.

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