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Identification and treatment guide for potted plant diseases

Prevention of plant diseases indoors

Healthy indoor plants can withstand and fight pests and diseases much better than weak plants. To keep your houseplants strong, you need to meet their cultural requirements, which means using proper soil, avoiding draft, not cramped plants, and then maintaining a good balance between temperature, humidity, light, water and drainage.

A sick plant by Anna

All plants have different requirements and if you are not sure what these are, check out our Plant Hub to find out what balance and care your particular plant needs to thrive.

Chances are, however, that you are on this site because prevention is too late and you have suffered something nasty and want a treatment and you want it now! Trust us when we say, we feel your frustration. However, everything is not lost and the rest of this article offers some solutions.


The eight most common diseases affecting houseplants are listed below along with the identifying symptoms and a suggested treatment. If you have any problems with anything else let us know in the comments and we will try to help you.

Sometimes your plant will have a pest problem rather than a disease, in which case you will need to move on to our pest guide.

Crown and Stem Rot (Basal Stem Rot)

This is caused by fungal mycelia that live in most soils. It normally lives calmly with the houseplant, but when conditions become very humid by over-watering, cool conditions or poor ventilation, it multiplies quickly and infects the plant.


Black or discolored rotten spots at the bottom of the plant. It usually affects the base as this is the closest part of the soil and therefore the fungus, although it is possible that other parts will be infected instead. Succulents and cacti are most vulnerable.


The only treatment is to cut out rats and dust with an antifungal agent such as sulfur. If the base has been performed very poorly there is very little you can do to obviously if you have to cut out the entire lower part of the plant you will kill it. It is therefore worth taking cuttings from the healthy parts and trying to spread the exchanges.

Gray mold (Botrytis)

gray Form or gray Form is caused by airborne fungi that land on damaged or dying tissue. Small wounds are normal on plants, if it is healthy and conditions are reasonably dry it should not be a problem. The question arises when the plant is still weak and the surrounding atmosphere is moist and cool.

Botrytis blooming on a strawberry


Soft rotting patches soon covered in a gray fungus. There will more than likely be dead brown spots on leaves or stems, white or light brown spots on petals or rotten on bulbs etc.


Remove the infected parts of the plant. In the future, ventilation improves or finds ways to reduce humidity. If the mold has gone out of hand you may need to throw it completely.


If you have never fed or refluxed your plant, a nutritional deficiency is quite likely. Most plants produce their own food through photosynthesis, but small levels of nutrients are needed to maintain the new growth and to ensure a healthy appearance.

Nutrient deficiency in plants leaves

The nutrients are found in the soil but when they are gone they are gone and therefore the important nutrients are replaced either with a fertilizer or by changing the soil sometimes.


There are many symptoms of nutritional deficiency in houseplants, although you will usually experience unusual or poor growth. The leaves can be very small with odd shapes, the color of the plant can be dull or transparent in places. No flowers or flowers that are discolored or aborted before they can be opened can be symptoms.


The immediate treatment for your plant is to either fertilize using a mixture of all purposes or to repot with fresh compost. Just select one to start with, rather than both at the same time as it can lead to too much fertilizer that can damage the plant further. The rule of thumb is to wait at least 8 weeks before you start fertilizing newly repotted plants.

Powdery mold

Fortunately, powdery mildew disfigures rather than deadly. It is also not too common for indoor plants because it is caused by fungal spores moving through the wind.

Photo showing powdery mold leaf

Obviously if you have your houseplants outdoors in the summer, you increase your risk. Hot, moist places and plants that are very close to each other increase all your chances of the fungi grabbing and spreading.


A white film that looks like a light dusting of flour covers the leaves, over time the white appearance can become dull and darker. If left unchecked, it will spread throughout the plant, including stems and flowers.


Carefully remove the badly infected moldy leaves (you don’t want to act like an artificial wind by blowing the spores around other plants). Then spray with a product containing Myclobutanil, Penconazole, Flutriafol or dust the leaves lightly with sulfur to provide control.


Rust is a common disease of roses outdoors but inside it is quite rare.

If you grow roses, chrysanthemums, pelargoniums or fuchsias as houseplants, you need to watch out for infection as eradication is very difficult. Therefore, if it is suspected of rust, you must isolate it from other houseplants to prevent it from spreading.

Rust on the leaf on a rose


Brown rings or spots on the leaves. They usually start on the underside, although they can appear on either side in more advanced stages. The leaves can fall prematurely without yellowing before the hand and often when you gently brush past.


Normally, complete eradication of Rust is difficult and you may just be able to control it. However, carefully remove the infected leaves and try not to shake or beat the rust spores from the slices, as this will only spread the infection to other parts of the same plant or near neighbors. If this does not work, any chemical product containing Mancozeb, Penconazole or Flutriafol should help.

Sooty Mold (or Form)

This is a disease that has a very visible presence. It is not really a direct attack on the plant but rather on honey dunes that are produced as a waste product by several pests, such as Skala.

Sooty mold on an umbrella plants leaves

The honeydew is a clear subject but in some viewpoints you can see it as a sticky residue. As soon as the room becomes humid and less ventilated, maybe when the winter is approaching and we close the windows and turn on the central heating, the fungus grabs and all previously clear residues become green-green and moldy.


Black or dark green soot that stains. In extreme cases, it will cover entire leaves as in the picture above.


Sooty Mold does not directly damage the plant but it is awful and uncomfortable to watch. You can remove it by wiping the leaves with a damp cloth. Then rinse the leaves with clean water. Make sure you erase the pest problem at the same time to prevent future attacks.


Viruses are a broad subject, the symptoms vary and most types of plants are performed occasionally. They are usually spread by long-lasting pests such as aphids or by the fact that the plant is near one that has already been affected by a virus.

Plant virus in an orchid leaf


There are many symptoms of a plant virus and they may appear differently depending on the type of pot plant that has been infected. The growth can be distorted, twisted or distorted. The leaves may be yellowish or mottled in spots, mosaics or stripes. All flowers can be streaked or not developed properly, ie they can be ripe and open but still have a green color when they should be something else.


There is no cure. If the symptoms cannot be tolerated, you must throw it away. Do not attempt to spread any part of the plant as there is a great possibility that the virus will remain and bloom in the new plants.

White mold (or Form)

What is the white mold that grows in my potted soil?“Is one of our common questions. It is another fungus that quickly colonizes the soil surface when conditions are humid, humid and watered.

The ventilation is also usually poor, therefore it tends to look more during cooler months of the year when everything in the home holds. Don’t worry though, as white mold is easily handled and basically harmless to plants and people.

White mold in house plant soil


The soil surface is coated in a white fluffy substance that looks like cotton wool.


You do not have to suffice for the sprays here. All you have to do is gently shake up the affected ground with something like the end of a pencil or pen. You don’t have to pick it out or anything like that so it’s a very easy job. The shaking can release the fungal spores in the air, but be careful not to inhale them as they can potentially trigger allergies and aggravate asthma.

After delivering the treatment, consider moving your plant to a more ventilated space or trying to release the culture medium by making it more “open”.

About Elisa

I love flowers and bonsai trees

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