If brown spots spread on a cactus, this damage can be attributed to various causes. In most cases, errors in care are responsible for the dilemma. Diseases or pests are less common. We have compiled the most common causes with tips for the right course of action for you here.
Cacti sometimes react to too much moisture with brown spots
These care mistakes cause brown spots
Cacti react to failures in the care program with brown spots on the prickly epidermis, among other things. This applies both to an unsuitable choice of location and to an unbalanced water and nutrient balance. Common causes are summarized in the following overview:
- Nutrient deficiency: Fertilize cacti every second watering from May to September
- Waterlogging: During growth, allow the substrate to dry out almost completely and then water thoroughly
- Wrong hibernation: from November to February keep bright and cool at 5 to 12 degrees and do not water
Although cacti are sun worshipers, they can still get sunburned. If the plants move to their regular spot in full sun on the window sill after the winter period, they should first acclimate to the partially shaded location for 8 to 10 days. This precaution is also relevant if you put your cacti on the balcony in May.
Sucking pests leave brown spots
If negligence in care can be ruled out as the cause of brown spots, you are very likely dealing with pest infestation. Stinging and sucking insects injure the epidermis, causing brown spots to develop there. Spider mites are among the culprits, as are scale insects and aphids. Examine the affected cactus with the magnifying glass to locate the pests. In the early stages, the infestation can still be combated with simple home remedies:
- Scale insects dab with alcohol-soaked cotton swabs or dust with diatomaceous earth
- Spider mites and aphids spray with the classic soft soap solution
By placing the infested cactus in an airtight plastic bag for 3 to 5 days, you cut off the supply of oxygen to the pests and their offspring.
tips
When cacti get old, various species tend to cork. This is a natural process in the course of which the tissue lignifies, which can be recognized by brown spots. Young cacti, on the other hand, react with corking to excessive humidity and watering with cold, hard tap water. Moreover, epidermis corks when the cactus suffers sunburn.