If a white coating spreads on cacti, their appearance and vitality are equally affected. You can find out the two most common causes of the problem here. Use our tips for effective combat with natural remedies.
What causes white plaque on cacti and how can you combat it?
A white coating on cacti can be caused by powdery mildew, a fungal infection, or mealybugs, pests. Mildew can be controlled with milk water or primary rock powder, while mealybugs can be treated with alcohol, spirit or soft soap mixtures.
Cause 1: Mildew
Powdery, white coating on the green epidermis indicates the fungal infection mildew. As the disease progresses, the infected parts of the plant turn brown and die. How to act correctly now:
- Cut off severely affected plant parts and dispose of them in household waste
- Treat the cactus with a mix of 1/8 liter of fresh milk and 1 liter of lime-free water
- Spray the milk water every 2 to 3 days
- Alternatively, dust the affected plant with primary rock powder
For cacti in the greenhouse, get help from the animal kingdom. Mushroom ladybirds (Psyllobora vigintiduopunctata), sixteen-spotted ladybirds (Halyzia sedecimguttata) and squirrel hoverflies (Myathropa florea) enthusiastically browse the mushroom lawn.
Cause No. 2: Mealybugs
If the coating resembles small, white cotton balls, you are confronted with a pest infestation. These are 1-5 mm small mealy bugs and their larvae. The parasites protect themselves with a waxy shell and suck up the plant sap. Upon contact, a greasy, white plaque is formed, so the pests are also known as mealybugs. This is how you take action against the plague:
- Dab individual infested areas with alcohol-soaked cotton swabs
- Spray large areas with alcohol or lemon balm
- Alternatively, fight with a mixture of 1 liter of water and 15 ml each of soft soap and spirit
The use of beneficial insects has also proven successful in combating mealybugs. This particularly applies to locations such as the greenhouse, hothouse or winter garden. The Australian ladybird (Cryptolaemus montrouzieri) has lice at the top of its menu. The beneficial insects are bred in special farms and can also be purchased there.
Tip
If the coating on cacti appears more grayish than white, you are dealing with gray mold (Borytis). This fungal infection often occurs on desert cacti that are placed in a humid location. In the early stages, an immediate change of location to a sunny, air-dry place can help. Otherwise, you will not be able to avoid disposing of the affected cactus.