White spots on succulents are a cause for concern as they often indicate a bigger problem at hand which needs your immediate attention.
White spots on succulents are most often caused by powdery mildew, insect infestation, excess salt, or edema. It is also possible that the white stuff you see on your plants is just farina.
What is farina?
Some types of plants, including varieties of succulents with glaucous leaves, develop farina or epicuticular wax.
This type of wax is a mechanism used by plants to help them cope with droughts. Apart from that, plants use the wax for protection from the sun and predators, especially insects.
In succulents, farina imbues glaucous leaves with a tinge of white, blue, or gray. If you try to wipe the leaves, the wax can be removed easily.
Although the wax tends to collect in the stems and the leaves, owners should not see this as a cause of concern and they should just let the farina remain and perform its functions.
You should not wipe the farina off your succulents. You can end up doing more harm than good. This is because of the critical functions of the wax on succulents. Worse, if you wipe the farina off your plants, it will take a long time for the wax to come back completely. This leaves your succulents looking patchy.
But how do you know if it is farina on the succulents or something harmful? In succulents that produce farina, you will notice that the whitish coat is more or less even. Typically the wax can be found on both sides of a leaf. Over time, farina can accumulate in some parts of a succulent.
You can distinguish farina from the harmful causes of white spots with the overall health and appearance of your plant. If your plant looks otherwise healthy, then you should not worry at all.
The presence of powdery mildew on a plant means that it is suffering from a fungal disease. Apart from the white spots, you will notice that some of the plant’s leaves become yellowish. Soon after, these leaves drop.
Mildew is harmful to your succulents because it competes with your plants by leaching vital nutrients from the leaves.
Unlike farina which coats plants evenly, powdery mildew looks patchy and fuzzy.
Usually, the infestation begins with one or two leaves. The white spots form slowly. And as such, some parts of the affected plant may not have white spots.
Powdery mildew infests plants during the summer, thriving under warm and dry conditions. The spores are spread by the winds, making infection between plants easy.
One of the best remedies for powdery mildew is milk diluted with water until you get a 10% solution. All you have to do is spray this solution over the affected succulent every week.
However, there are some concerns that using a milk solution to treat powdery mildew can lead to fungi developing resistance to the treatment. As such, you should alternate using the milk spray with other remedies for powdery mildew.
One part of baking soda mixed with two and a half parts of horticultural oil and a gallon of water is another effective solution against powdery mildew.
This baking soda solution helps affected plants develop their resistance against the fungi that cause powdery mildew.
But be warned: there are a few issues associated with using baking soda. For one, you will need to keep a watchful eye on infected plants. Baking soda can also accumulate in the soil which can leach off vital nutrients.
Powdery mildew can also develop on succulents during the winter due to the combination of low light, poor air circulation, high humidity, and low temperatures. Fungal spores can also accumulate on leaves that receive overhead watering.
You can avoid powdery mildew during winter by increasing indoor air circulation through the use of fans.
If you see powdery mildew on your succulents, cut off the affected leaves and apply the aforementioned solutions.
White spots on succulents can be a sign that you might be dealing with an insect infestation.
Whiteflies feed on the water and nutrients of the plants they attack. And as they feed on the plants, they leave a honeydew residue.
The larvae of whiteflies look white and fuzzy on affected plants. Usually, whiteflies leave their eggs on the underside of plants.
To determine whether you are dealing with a whiteflies infestation or not, check if the plant has mildew which is sticky to the touch.
Worm castings are effective both as a treatment and preventive measure. Worm castings, which is essentially worm manure, also doubles up as a fertilizer.
Plants absorb chitinase from the worm castings. This enzyme destroys insects by breaking down their tough outer shells.
For a whiteflies infestation, you can use worm castings as a foliar spray to target pests.
Another insect that can cause white spots on succulents is the mealybug. On infected succulents, mealybugs look like tiny balls of cotton.
Mealybugs can easily infect multiple plants, attracted by both overwatering and overfertilizing. These bugs commonly infest indoor succulents, although it is not unusual to see them on outdoor plants.
An infected plant will have whitish webs in its crevices.
To get rid of mealybugs, you can soak up balls of cotton in isopropyl alcohol. Alternatively, you can spray the alcohol directly on the insects.
Spider mites can lurk beneath leaves and stems of succulents or even in the soil. Technically, these small critters are not insects. Rather, they are arachnids, related to ticks and spiders.
Spider mites feed on the juices of succulents. A colony of these arachnids can kill an affected plant in a matter of days.
Although spider mites are not easy to detect, they can leave signs of damage, usually on the parts of the plant they feed off. Infected plants usually have small spots which may be white, yellow, or brown.
Get rid of spider mites by spraying alcohol directly on the infected plant.
Excess salts and edema
Some plants, like the jade plant, store water in their leaves.
Now sometimes, the rain and groundwater in your area might have a significant concentration of salt. In jade plants, white spots appear when they transpire or evaporate water.
This leaves excess salt on leaves. The presence of excess salts on the leaves is not necessarily harmful and can be quite easy to remove.
All you have to do is to wipe off the salt with a moist cloth.
Another water-related cause of white spots in jade plants is edema. This condition occurs when the plant takes in more water than it needs, often a result of overwatering.
The increased uptake of water causes the formation of blisters on the plant. Although the plant can recover with reduced watering, be aware that the blisters will remain on the leaves.
Should you worry?
You do your best to take care of your succulents. And as such, it can be disheartening to see unusual blemishes on your plants.
Before you panic, determine the possible cause of the white spots on your succulent. It can be just farina or excess salt or something more alarming like powdery mildew.
If you are unsure what is the actual cause of the white spots, consult the experts in your area. Alternatively, you can join online fora and ask members for help.
Image: istockphoto.com / jaboticaba