With humble requirements and very few pests and diseases, succulents are some of the easiest plants to grow. Their natural environments are very harsh and arid habitats, so they’ve learned to thrive in scarcity. However, succulents are not impervious to maladies. Like many plants, they also have mold problems that can severely affect their health and beauty.
Most problems with succulents come from overwatering, mold infections included. Elevated levels of moisture or prolonged dry periods invite different types of pathogenic fungi that can quickly colonize the plants under favorable conditions. Prevention is essential when it comes to any plant disease, with a good watering regime and hygiene playing a pivotal role. But sometimes mistakes happen, and you find your beautiful succulents covered in fungal growth. If you notice a white, powdery substance on the leaves of your succulents, it is very likely that powdery mildew is the culprit.
Since powdery mildews spread easily, it is best to act promptly and tackle the problem as soon as possible. Powdery mildews affect only the top layer of plant tissues and are rarely lethal to plants. However, they can reduce their photosynthetic capacity and weaken them, decreasing their aesthetic appeal. To help you deal with this nuisance, we’ll mention some of the best-proven methods of treating this fungus on succulents.
Note: The term ‘white mold’ is an umbrella term that refers to different species of mold with white mycelium, but most commonly to Sclerotinia sclerotiorum, a fungus that attacks numerous species of flowers and vegetables. Ornamental succulents are rarely hosts to this pathogenic fungus, so the term ‘white mold’ here applies to powdery mildews.
Isolate infested plants
The general approach to managing powdery mildew on most plants is to remove the infected parts at the first signs of disease to prevent the infection from spreading further. However, since removing leaves of succulents spoils their appearance and aesthetic beauty, this approach is not favorable for them. The best alternative is to separate the infested plants from healthy ones to prevent disease spread and treat them with suitable fungicides.
Use fungicidal sprays
Powdery mildews won’t go away on their own, so it is necessary to use adequate fungicides. There is a wide variety of compounds that display fungicidal activity against powdery mildews. You don’t need to run to the store to buy them, as you probably already have some at home. Since we advise against the use of synthetic fungicides, we’ll mention here some of the most effective natural solutions.
Baking soda
Baking soda is an essential tool in every household. From a multi-purpose cleaner to treating stomach acidity, baking soda is a cheap, effective natural solution to numerous problems. Its utility in the garden is also unprecedented – mixed with water and a bit of soap, it becomes an organic fungicide and insect repellent.
You will need:
- one tablespoon of baking soda
- half a teaspoon of soap (preferably Castille soap)
- one gallon of lukewarm water
Mix the ingredients thoroughly to ensure an even distribution of the active components. It is very important not to put too much baking soda in the mixture, as it can damage the plant leaves. If you’d like to broaden the spectrum of its activity to include pest control, you can add one tablespoon of horticultural oil to the mix.
Note: A mix of baking soda and water can be used as a preventive treatment, but it won’t be effective on already infested plants. The addition of soap or horticultural oil is a must.
Apply the mixture once a week, all over the plant, including the underside of the leaves. The treated plants shouldn’t be left in the sun, as they are susceptible to burns. Use the mixture immediately, and don’t store the leftovers for future use. If you don’t see any positive progression after four weeks, strengthen the solution by adding one tablespoon of neem or jojoba oil into the mix.
Vinegar
Another all-around household item effective against powdery mildews is vinegar. However, due to its acidity, it is very important how much you apply since the vinegar can damage the plant along with the mildews.
You will need:
- two or three tablespoons of vinegar
- one gallon of water
Dilute two or three tablespoons of apple cider vinegar in one gallon of water and shake well. It is best to test the solution on a leaf before applying it to the whole plant. If you notice any signs of burns on the leaf, dilute the solution with a bit more water. Apply the mixture once a week for 3-4 weeks.
Neem oil
Neem oil is an essential oil extracted from the neem tree with incredible broad-spectrum insecticidal and fungicidal properties. It is a very potent pesticide, so it shouldn’t be used in case of weak infestations. Neem oil can be applied as a soil drench or foliar solution. The former is used against insects, while the latter is effective against powdery mildews.
You will need:
- two tablespoons of neem oil
- one gallon of water
- a drop or two of soap (non-detergent, preferably Castille soap)
Shake the mixture well, and depending on the severity of infestations, apply it once a week or once every two weeks until the mildews are gone.
Sulfur
Elemental sulfur has a long history of use in agriculture as it is the oldest known fungicide. It has been used for over two millennia in treating rusts and powdery mildew on cultivated plants. The first records of its application come from Ancient Greece, and it remained an important tool for controlling plant diseases ever since. Sulfur is best applied preventively, but it can also treat the already infested plants.
You can find sulfur fungicides in most plant stores. The way of application can vary depending on the type of formulation, so make sure to follow the instructions on the label. The effectiveness of sulfur fungicides is temperature-dependent, so make sure to apply them at temperatures between 60°F and 80°F. Lower temperatures decrease the activity of sulfur, while higher temperatures can cause burns on plant leaves.
Note: Don’t mix fungicidal oils with sulfur, or apply the oils within 2 weeks of sulfur application since they can damage the plant tissues.
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Ana Mileusnic
Ana is a scientific writer and researcher passionate about sustainable agriculture and environmental protection. As a speleologist in training and a member of the Bird Protection and Study Society of Serbia, she is involved in field research and various projects related to ornithology and biodiversity conservation in her home country.
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My one succulent plant which is pretty big and has new growth where the larger leaves have black rings on them not sure what todo w are getting a large amount of rain almost everyday and it’s also in 80% sun. I’ve been removing those black almost mold but it’s round circles oddly. Help