Indoor Plant Disease Identification

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House plant diseases tend to be fungal rather than bacterial or viral. The most likely are here in this guide to indoor plant disease identification. If the symptoms don’t match, check the further resources section for where to find more information.

Landscaping Ideas

A Healthy Environment

As with preventing pests, infection is much less likely on healthy plants, so look after them well. Good housekeeping is also essential to avoid cultivating an atmosphere in which disease could take hold. Also to prevent spreading any existing disease. Keep plants tidy, removing dead leaves and other detritus from around the base of them. Make sure tools and equipment, including the pots themselves, are clean, by washing with soap or other detergent and hot water. If the plants’ compost develops mould on its surface, repot it, washing off the roots entirely before replanting in fresh compost.

Fungicidal sprays are available to treat some diseases but reserve them for only when they are necessary. Select a treatment which is specific for the condition you have identified and always read the label before choosing a product. Make sure that you follow all the manufacturer’s instructions, including maximum dose, spray and harvest intervals.


Also known as grey mould and, to wine-makers, noble rot. Spores are ever-present in the air, everywhere, and readily infect dead or weak tissue, before spreading to the rest of the plant.

Signs of damage: Fluffy grey moulds developing quickly on leaves and stems, or spots on petals.

Control: Prevent infection with good air circulation and by promptly removing dead or damaged tissue with neat cuts to minimise open wounds. Remove and dispose of infected tissue, trying to contain it in the process, to avoid spreading more clouds of spores.


Both powdery and downy mildews are fungal diseases which cause white mould on leaf surfaces.

Signs of damage: Patches of white mould; powdery on the upper side, downy on the underside with corresponding yellow patches above. Leaves yellow and die; inhibition of growth is evident.

Downy Mildews

Downy mildews invade plant cells, and only the spore-bearing structures show on the leaf surface as a white or grey fuzz. Early stages of fungal attack can be seen as yellowish blotching on the lower leaf surfaces. These blemishes are followed by a bloom of white or greyish-white spores, and if left untreated, the plants may be severely crippled.

Powdery Mildews

Plants suffering from these diseases are easily recognised, as their leaves, stems, flowers or fruit may be covered with a white-grey powdery coating. The fungus causing the disease may be specific to the host plant; for example, rose mildew will not affect any other type of plant, or it may have a broad host range attacking many varieties of herbaceous plants. The disease is superficial, but if it is not combatted, it may result in a loss of leaves.

Control: powdery mildew often infects plants with dry roots and wet leaves, so ensure proper air circulation and correct watering. Downy mildew is also characteristic of damp environments and usually affects young plants. Remove affected parts as soon as they are seen and improve the atmosphere around the plant.


These tend to be brought in via the plant or occasionally through infected pests or tools.

Signs of damage: The whole plant will become stunted or distorted, with yellow spots or streaks on the leaves.

Control: It’s impossible to treat a virus, so the plant must be disposed of, and all tools and equipment thoroughly cleaned afterwards to avoid the infection spreading to other plants.

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10 thoughts on “Indoor Plant Disease Identification”

  1. Interesting, I didn’t know that disease in indoor plants is usually fungal. Does that mean we often have to damp living areas and this is why the fungi and mould develops? 

    You mentioned to use fungicidal spray on the plants. I was wondering, if you do that isn’t that harmful for human health? I mean, sure fungicide is targeted to kill fungi but it’s still a chemical and if it’s in the air you breath and your skin when you touch the plant is gets in your bloodstream? Am I too paranoid or is there some truth in this?



    • Hi Katya – thank you for reading my article and asking questions. Yes, fungal growth requires wet material to develop, which is why damp living conditions can encourage it. Fungicidal sprays need to meet a country’s regulations to ensure they are safe to use. All the best, Diane

  2. It has to be said, sad though it is, that I have almost all but given up on indoor plants. The few large ones we had fifteen or more years ago, died of a severe overdose of children. Then they grew, the children that is, but I couldn’t bring myself to revisit.

    However, I have on many ocassions, tried my hand at Bonsai’s with some success but it never lasted. My wife even bought me a twenty year old one, which died within a couple of months. It makes me think that the house is inherently toxic.

    We have a conservatory which backs on to he kitchen, the opening between has a large shelf area. This is where we have propogated many plants. I have even managed to grow some Bonsai from seed, only for them to die once they’ve started to sprout leaves. One of the major concerns I have is the soil area. It seems to grow a white ‘fur’. It seems similar to your description of Botrytis but it’s never on the leaves, just the soil. I scrape it off and it extends the life. Every single pot does the same.  I’ll keep being vigilant.

    • Hi – thank you for reading my article and leaving an interesting comment. How sad that you managed to kill off a twenty-year-old bonsai! It does sound as though your soil is a problem, and not something I have seen before. I hope you are more successful in the future with your house plants. All the best, Diane 

  3. Hi,

    Thia is a very informative article about plant diseases.  I learned a lot about fungal, bacterial and viral diseases. It’s very important to look for these systems and take necessary actions to cure or prevent the diseases from further spreading. That is indeed on of the major aspects of house keeping. I saw that you have recommended some seeding starter trays as well. All in all this article has covered many aspects of indoor planting. I enjoyed reading this. 🙂

    • Hi – thank you for stopping by and adding a comment. I am pleased you have learnt something new, and I hope you put my advice to good use. All the best, Diane

  4. Hi, Diane.
    Thanks for sharing your thoughts on the disease identification of the indoor plants.
    Though proper air circulation and correct watering can prevent maximum fungal diseases, I will follow your suggestions to contain the problem in the initial stage itself. Viruses are something I always get scared of. Throwing a loved plant infected with a virus gives a very unpleasant feeling, but as you said, there is no other alternative.
    Warm Regards,
    Gaurav Gaur

    • Hi – thank you for reading my article. I am pleased you will be following my suggestions, and hopefully, you will have no more diseased plants. All the best, Diane

  5. Great topic. Everything in this article is clearly explained and understood.In recent years there have been many plant diseases.These diseases have largely been a stumbling block for many farmers.Unfortunately many farmers have been unaware of the correct symptoms of plant diseases. This article will be of great help especially for indoor growers. I wish you all the best.



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