Brown Spots on Cactus Plant: Causes and Remedies

If there are brown spots on cactus plants, this damage pattern can be traced back to various causes. Most of the time, mistakes in care routine are responsible for the problem. Diseases or pests are less common. We have compiled the most common causes with tips for the correct course of action for you here.

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1,000 Types of Cactuses with Pictures

Care Mistakes that Cause Brown Spots

Cacti react to mistakes in the care routine with brown spots on the prickly epidermis. This applies to both an unsuitable choice of location and an unbalanced water and nutrient intake. The following overview summarizes common causes:

• Nutrient deficiency: Fertilize cacti every second watering from May to September
• Waterlogging: Allow the substrate to dry out almost completely during growth and then water it thoroughly
• Incorrect overwintering: From November to February place in a bright and cool place at 5 to 12°C and do not water

Although cacti are sun worshipers, they can still suffer from sunburn. If the plants move to their regular full sun spot on the windowsill after winter time, they should first acclimatize to a partially shaded location for 8 to 10 days. This precaution is also relevant if you put your cacti on the balcony in May.

Pests that Leave Brown Spots on Cacti

If negligence in care can be ruled out as a cause of brown spots, you are very likely dealing with pest infestations. Stinging and sucking insects injure the epidermis, and so causing brown spots to develop. Spider mites are also among the culprits, as do scale insects and aphids. Examine the affected cactus with a magnifying glass to identify 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 packing the infested cactus in an airtight plastic bag for 3 to 5 days, you cut off the oxygen supply to the pests altogether.

Read also:
How to Get Rid of Cactus Bugs

Pro Tip:

When some types of cacti are getting old, they tend to cork. This is a natural process in the course of which the plant take a woody appearance, which can be recognized by brown spots. Young cacti, on the other hand, react by corking when the air humidity is too high and if watered with cold, hard tap water. In addition, when the cactus gets sunburned, the epidermis becomes corked.