Cacti - common diseases and pests

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Cacti - common diseases and pests: diseases

Cacti are inherently robust against diseases and pests. If they get sick or become infected, the cause is often a mistake in the care. For this reason, damage can usually be well prevented if some points are considered.
Tiny small or large in size - cacti come in many forms. Their high resistance is common to them all. Nevertheless, diseases or pests can occur on them. But with the right care, infestations can usually be prevented well. And once the cactuses have fallen ill, the appropriate measures quickly help. However, of course, the corresponding knowledge is required to make a quick and targeted intervention in the first place possible.

Prevent infections and infestations

Cacti are basically healthy and resilient plants that are generally less susceptible to diseases and pests. The already strong immune system of the succulents can be further increased. It is best to treat the cactus to a place outdoors in the summer. Unfiltered sunlight, rain and fresh air harden the plants. As well as the temperature differences between day and night. A cooler winter quarters - which of course should be adapted to the particular type of cactus - gives the plants the necessary rest period. This also makes it possible for the plants to defend themselves against pathogens.

Mistakes in care

Many diseases and even a pest infestation can be attributed to errors in the care of cacti. Probably the most common - albeit well-intentioned - mistake is found in the casting. Since the cactus is optimally adapted to dryness, it can not deliver too much moisture or only to a very small extent to the environment. As a result, it builds up in the substrate and the plant itself, which leads to rot and weakens the plant as a whole. In addition, it can cause the plant parts to burst. If culture or location are not optimal, further typical symptoms will be seen. including:
  • yellowish discoloration and soft plant parts
  • reddish discoloration
  • thin, feeble and bright shoots
  • premature dropping of buds
If the cactus turns yellow and wrinkled, there are two possible causes for this. Limited to the cold season is the possibility of frost damage. If the plant is moved to a frost-free place, the damage is at least not increased. A complete recovery is not guaranteed. Throughout the year, there may be an oversupply of water that comes about, for example, through rain. Changing the substrate and drier in the future can save the cactus.
If cacti become reddish, they are sunburned - protection against blazing sun is already sufficient as a measure. If the shoots are powerless, are strikingly bright and thin, the reason is also found in the light and water. The cacti are usually too dark, too warm and too humid. If some buds fall off, this is no cause for concern with the cactus. Many species simply do more than actually bloom. If there are a large number, however, the conditions on the site should be checked - too little light, heat and water are possible causes. Once you find bud approaches, the cactus must not be rotated anymore.



The possible diseases of cacti are rarely of a bacterial or viral nature. If it is such an infection, affected plants show growths and reduced growth. If only small areas are affected, the possible salvation lies in removing the diseased parts. This is done generously with a sharp, disinfected knife, which does not seem healthy. Both interfaces and used tools are then disinfected again. Suitable agents are hydrogen peroxide and potassium permanganate. Significantly more often than viruses and bacteria occur on the cacti mushrooms. These always have easy play when the cactus is too moist. including:
  • Epiphyllum mosaic disease
  • Anthracnose
  • Stem rot (Helminthosporum)
  • Root rot or stalk rot (Phytophthora)
  • Black soot dew
  • RhizoctoniafĂ€ule
  • PhythiumfĂ€ule
Epiphyllum mosaic disease
The Epiphyllum mosaic disease is one of the most common fungal infections of cacti and is unfortunately hardly curable. The most obvious symptom is yellowish, bright spots that visibly sink in. The cactus should first be isolated so as not to infect other plants. A tentative cure is possible but not likely by removal of the affected areas and subsequent disinfection.
As the name suggests, the focal spot on the cactus is characterized by brownish spots that look burnt. The spots become hard and partially cracked.As a first treatment, they should be cut out with a sharp knife and the open areas should be dusted with activated charcoal. If this does not succeed, a fungicide must be used.
Stem rot (Helminthosporum)
The stem rot usually penetrates into the plant through injuries, the pathogens originate from the substrate. Affected areas become soft and glassy. If cutting above the infected area and changing the substrate, at least the head of the succulent plant can be saved.
Root rot or stalk rot (Phytophthora)
The cactus rots from the bottom up. The treatment is the same as for the root rot.
Black soot dew
The name already reveals the appearance of the Rußtaupilzes, because this manifests itself as a black surface. It can easily be treated with fungicides on cacti.
The RhizoctoniafÀule manifests itself by a white mushroom coating on cactus and substrate. Affected plant sections appear glassy and soft or even slimy. Fungicides help with low infestation, in case of extensive spread still healthy sections of the cacti can be removed, disinfected and replanted.
Pythium rot is a typical stress disease affecting cacti with weakened immune systems. It too manifests itself in white coverings - but its appearance can take many forms. Remedying again the removal of the affected areas and a treatment with fungicide.


The list of possible pests on cactuses is long, but in fact they rarely occur. These include:
  • snails
  • mice
  • Ova or nematodes
  • various lice, such as leaf, shield, lice and mealybugs
  • fungus gnats
  • spider mites
  • White fly
Snails and mice
The damage of these animals can be recognized quickly by the large food marks. In both cases, a raised location helps to reach neither mice nor snails.
Ova or nematodes
The ova or nematodes are roundworms that often serve as beneficial insects in the garden. These uninvited guests cause the cactus usually bulky growths and limited discoloration. A rescue attempt can be started if the infestation is still low. For this purpose, the substrate must be changed thoroughly and the growths are removed.
Lice are well recognized by the cacti regardless of their species. Outdoors, the best combat is the use of ladybirds, lacewings or parasitic wasps. Yellow board and insecticides also help.
fungus gnats
Mourning gnats are actually flies that are black and small in color. They lay their eggs in the substrate and are quite easy to fight with a little patience. Adhesive traps and substrate changes are usually sufficient.
spider mites
Spider mites can infest the cactus especially when it is in dry heating air. To get rid of them, the cacti are showered or sprayed well with water and packaged airtight for two to three days in a bag. The warm-humid climate does not get the mites.
White fly
Once white flies have established themselves, they can ascend as a whole swarm - when casting this is immediately noticeable. Yellow boards, substrate changes and the use of ore wasps or parasitic wasps are suitable for controlling. Just as airing, because these pests prefer a very humid and warm climate, dryness and cool fresh air expels them, however.

Frequently asked questions

  • How do I prevent infections between my cacti?
Infection with diseases or skipping is quite common. It can be avoided if the plants are basically not too close to each other. Sick cacti must be isolated immediately. In addition, all scissors, knives, pots and other aids must be thoroughly disinfected after each use.
  • Can I lug in diseases and pests?
No matter how beautiful a new cactus may be - it also always poses a threat to the plants that already exist. Infestations can not always be recognized immediately, so each new acquisition is quarantined for three to four weeks - in other words, an isolated location should be.

Worth knowing about the care

If you really want to take care of cacti, you have to pay a lot of attention. Although the prickly plants belonging to the succulents family are quite undemanding, they nevertheless thank the owner for appropriate care with good growth and, depending on the species, also with unusual flowers. In general, it can be said that the most important factors in the growth of cactuses are light, soil and water. Some interesting cacti and succulents: carrion flower, aloe vera, bishop's cap, prickly pear, Christmas cactus.
  • All cactuses should be very bright. The window sill is best suited to a window in which the sun shines powerfully.
  • But even outside, cacti are good at least in the summer months.
  • However, they must be protected from bad weather periods with lots of rain.
  • With too much moisture, the cacti can enter quickly.
  • If the cacti are to be housed in the greenhouse, it is important that this has sufficient ventilation options.
  • Otherwise, extreme temperatures develop here, which are not necessarily conducive to the heat-accustomed cacti.
Often it comes to so-called misery. That is, the cacti form extremely thin and long shoots, which are not only ugly, but can also be harmful to the health of the plant. Every cactus will enter the middle of the room or even on a shelf, because there is far too little light here. Such places should be avoided. If one is unsure, one can also measure the light conditions at the prospective location with special light meters. So you can quickly find out if this is suitable or not. But the soil in which cactuses are planted is also crucial:
  • So you should mix garden soil with permeable layers such as sand, gravel or potsherds.
  • It is important that the earth is not too large and the soil is very well permeable to air and water.
  • Although you can use the commercially available cactus clay, but mixing with sand or gravel is much better.
When casting, be sure not to do too much of a good thing. For how many cactuses have been truly drowned by overly affectionate flower lovers? Of course you should know that waterlogging is deadly for cacti. This rots the roots and the rot quickly spreads over the whole plant. It is then irretrievably lost. In general, cacti should not be watered in winter.
Cacti are inherently robust against diseases and pests. If they get sick or become infected, the cause is often a mistake in the care. For this reason, damage can usually be well prevented if some points are considered.

Video Board: Scale on Prickle Pear Cactus.

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