Is Your Cactus Prone To Diseases?

A cactus’ health depends on various factors, including water supply, exposure to sunlight, location, climatic conditions, etc. If any one of the specific requirements is not met, it can cause direct or indirect harm to the cactus. 

Different cacti tend to have different requirements in terms of these factors. For instance, cacti that grow in tropical rainforests require more water while desert cacti prefer longer periods of exposure to the sun and minimal, infrequent watering. If a tropical rainforest cactus is exposed to intense sunlight, a sunburn can be inevitable.

Knowing your plant is the first step towards protecting it. Cacti require very little care, but the right kind of care. Without it, they are undeniably more prone to a multitude of diseases.

In this article, we have classified the following diseases based on if they are biotic or abiotic.

Abiotic Problems That Affect A Cactus

Many of the issues that your cactus may go through are not caused by living organisms. It depends upon abiotic factors such as water, drainage, exposure to sunlight, rainfall, etc. 

Overwatering

The most common problem that most beginner cacti enthusiasts face is the amount of water they give to the cactus. Cacti hate excess moisture, and any more water than is needed has direct negative effects on the plant. 

If a cactus is overwatered, the water will naturally spend more time in the soil surrounding the roots of the cactus. This will lead to root damage, and the plants will slowly succumb to root rot. They will eventually lose their trademark green color and become mushy. 

Cacti require infrequent watering, with one watering per 10-15 days for the average cacti. 

Soil Drainage

The ideal soil for a cactus is fast-draining. If you are using poor draining soil, even with the right watering frequency, you are running the risk of root damage. 

Coupled with overwatering, this issue can lead to the imminent death of the plant. 

Exposure to Sunlight

Cacti love being under the sun, but even that has a limit. If you’re growing cacti that prefer being in the shade, exposure to intense sunlight can quickly lead to sunburns. You will be able to see yellowing in some areas of the cacti.

Sunburn usually attacks the areas that are not accustomed to sunlight first. The affected area turns yellow, discolors slowly, and then dies. 

Damage due to External Moisture

Misting is a great way to water succulents, but is a surefire way to inflict damage to your cactus. Any external moisture that comes in contact regularly with the stems or the leaves of the cactus will quickly make them decay. 

Knowing this, it’s important that you pick the best location for your cactus, keeping in mind the rain and humidity. If it’s potted, you can simply shift it indoors. If you’ve planted a cactus in the ground, an overhead cover is a good idea.  

Biotic Factors

The biotic factors causing diseases in your cactus can be further classified into microorganisms such as viruses and fungi, and pests and insects. There are a host of these organisms that can have life-threatening repercussions for your cactus. 

Cactus Dry Rot

Fungi like phyllosticta concava can have an adverse effect on your cactus if they infect it. This fungus will cause black spots to appear on your cactus, usually around or near the spines. Slowly, these spots grow up to a diameter of 2 inches.

Later on, you may also see callusing on the surface tissue of the plant, which is a sign that the infection has gone beyond repair. 

Since this infection is aggravated by soil moisture and can infect other plants as well, the best way forward is to remove the infected cactus and destroy it. Any other plants that were in the same soil should be repotted.

Cactus Stem Rot

Yellowing in a cactus is not only a symptom of sunburn but also a symptom of something far more serious. The fungi drechslera cactivorum can spell rapid damage to your young cactus, with its foremost symptom being yellow spots. These mostly begin at the base or the top of the plant.  

Slowly the rot spreads, turns pale yellow and then brown, forming small spore-like structures. Another potential symptom is disfiguration.

Drechslera cactivorum can do quick damage to your cactus seedling, taking less than one week to claim its life. In most cases, a stable dose of dicarboximide-based fungicide can help with damage control. 

Texas Root Rot

The fungus Phymatotrichopsis omnivora is notorious for affecting cotton plants adversely. It wreaks the same kind of havoc on cacti as well.

Once this infects a cactus, it will quickly spread on the root in higher temperatures. In most cases, you will be able to notice sudden wilting and discoloring of the cactus with no prior symptoms. If you uproot the plant, you will be able to see a brownish growth on the roots.  

Since there is no way to control the rot, isolating the infected plant is your best way forward. 

Just like fungi, viruses have also made their presence known as potential threats to cacti. 

Cactus Virus X

According to a study by the Institute of Plant Breeding, the recently discovered Cactus Virus X infects cacti by direct contact between the plants.

This virus usually starts showing symptoms during the flowering seasons, with the development of spots being a common symptom. The ensuing symptoms may vary from cactus to cactus and include disfiguration of spines, decay of body tissue, and even chlorosis. 

While its effects on the cactus’ physiology are still being debated, some of the studied effects include obstruction of the CAM (Crassulacean Acid Metabolism) photosynthesis and reddening of the whole stem. 

Researchers have prescribed good sanitation and decontamination practices while grafting and propagating cacti.  

Impatiens Necrotic Spot Virus

This virus is common amongst many plants, including flowering plants, tomatoes, and cacti alike. They spread through foreign entities, such as insects like thrips.

An infection leads to several issues in the cactus, like yellowing, necrosis, formation of lesions, etc. You will need to take the cactus to a plant clinic to get it diagnosed. 

The virus also spreads through vegetative propagation and is incurable, so isolation and destruction of infected cacti is the only way to protect other plants.

Diseases Caused By Pests

Red Spider Mite Infestation 

Red spider mites are tiny polyphagous pests that can infest various kinds of plants. They suck the sap out of cacti, thus emptying their cell content one by one. They make webs around the joints of the plant and lay eggs, reproducing rapidly. 

Rapid reproduction means that the plant weakens by the day. Due to their sap-sucking shenanigans, the plants are left with reddish-brown lesions that grow in size as these tiny mites grow in number. 

There are a lot of prescribed methods to get rid of this infestation, but timely action is required. Some of the most common methods are using rubbing alcohol or introducing their natural predators like phytoseiulus and even ladybugs. 

Cactus Scale 

Much like their mite counterparts, scale tend to suck on the sap of cactus, weakening the plant in cases of acute infestations. 

These small white pests are easier to spot compared to the red spider mites, but can still do quickfire damage to the cactus if not paid attention to.

The cactus starts getting brown corky spots that may easily be confused for corking. These insects can also expedite and exacerbate an existing corking process in a cactus.

Again, you can consult methods like biological control with the help of certain wasps and insects, and rubbing alcohol application. You can spray a mixture of water and rubbing alcohol (ratio of 1:1), with a few drops of dish soap added in, directly onto the cactus. Leave this on for 15 minutes or so, then rub the scale of the cactus.

Mealybugs

Unfortunately, pests (such as mealybugs) can make your cacti plants their home. Mealybugs feast on the sap in your cactus plant. This can ultimately lead to the plant’s death. Your plant’s vigor and vibrancy will suffer if mealybugs are present. Additionally, these pests secrete wax and sticky honeydew, which affects the quality and appearance of your plants.

If mealybugs are present near your plants, you need to take action as soon as possible. A larger population will feed on the cacti and inhibit growth. Most healthy plants can withstand a few of these bugs but not a larger infestation. Since cacti have a year round mild temperature, they are attractive to these pests.

If your cacti are indoors, mealybugs are attracted because they have no natural predators going after them. This is why you need to be the predator and check your plants for them. If you see them, take action to get rid of them. There are chemical options, but there are also some DIY options as well: 

• Dip a cotton swab in denatured alcohol and touch the bugs to instantly kill them. This is effective but must be repeated until all of the bugs are gone. 
• A fumigating smoke cone will cut down on the pest population. 
• Spray cactus with a solution made of 1 cup water with a few drops of dish soap mixed in. 

Mollusk Risk

Mollusks, like snails and slugs, are known to make a hearty breakfast out of plants. Cacti are also a delicacy they seem to enjoy.

If you grow a number of plants close together, the odds are there are a number of these small mollusks hanging around. At night, they venture out and attack the plants.

Your best bet at preventing that from happening is using a snail repellent like copper or other chemicals. Some of the repellants render these mollusks paralyzed and during the day, they tend to dry out and die.

Wrapping Up

Cacti are generally self-dependent, but cannot effectively tackle diseases without your help. In this article, we have discussed some of the most common problems and diseases along with their primary symptoms.

When it comes to these amazing desert plants, most diseases are incurable after a certain point of infection. Thus prevention and quick action is your best strategy for protecting your cacti.

Now that you are well equipped with some knowledge, you can quickly identify and diagnose some of these problems and work to remove them before they become lethal. Not only that, but you can also take preventive measures to ensure your cacti stay at their best.