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Indoor Plant Diseases: Discover the 10 Most Common

Fungal Leaf Spot Disease

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No matter how well you care for your plants, indoor plant diseases can strike with devastating results.

However, damage can be minimized if you know some of the early warning signs and quickly take the appropriate action.

This article covers the 10 most common types of indoor plant diseases, how to identify them and what to do should they attack your plants.

Before we look at the individual indoor plant diseases, it’s important to perhaps state the obvious, in saying that prevention is better than cure.You can help prevent plant disease by not contributing to the most common causes of plant disease which are;

  • Over watering
  • Under watering
  • Lack of ventilation

These can allow rots and other fungi to develop, so it would be worth your while to also check out this article ‘How to water indoor plants’.

The 10 Most Common Indoor Plant Diseases

1.Damping Off

Damping off

Problem: Seedlings are affected by damping off when the ventilation is inadequate, or seeds have been sown too thickly’

The seedlings will quickly collapse and die and you’ll notice a white fungal growth appearing on the soil mix.

Solution: Unfortunately, there’s no chemical cure for damping off. The best you can do is to ensure good ventilation and remove any plastic covering.

2. Downey Mildew

powdery mildew

Problem: Signals for this disease include green, yellow, purple or brown blotches on the leaves, and a mold- like appearance under the plant foliage.

The leaves may also turn yellow and fall off.

Solution: Bag and bin badly infected plants or remove affected parts of the plant.

There is no chemical solution for downy mildew. The best form of prevention is to avoid wetting leaves which can increase the chances of this disease.

3. Fungal Leaf Spot

fungal leaf spot

Problem: Dark spots with yellow edges appear on the leaves and the foliage may then fall off.

Solution: Remove any affected leaves as soon as you see them as well as any foliage that has fallen onto the soil mix.

Improving the ventilation around the plant may help prevent reinfection and if the problem persists, try using a fungicide.

4. Grey Mold

fungal leaf spot

Problem: First indications of grey mold usually include a fuzzy grey – brown mold on the plant’s stems and leaves.

This quickly leads to plant decay.

Solution: Remove the affected stems and leaves as soon as you see the mold and improve the air circulation around the plant.

Treat with a fungicide immediately or the plant may die.

5. Powdery Mildew

powdery mildew

Problem: You’ll notice a white powdery fungus on the plant’s leaves stems and flowers.

This disease is often caused by lack of ventilation and or water.

Solution: Make sure that you are not under watering your plant. This can increase the chances of infection.

Remove any infected parts as soon as you notice them and make sure that the plant is well ventilated.

If the problem is severe, then use a fungicide.

6. Root Rot

root rot

Problem: Because root rot occurs beneath the soil surface, it often goes unnoticed until too late.

It’s usually caused by over watering or long periods of drought. The roots look dark brown or black, then rot.

The plant wilts and will not respond to watering.

Solution: Unfortunately, there are no chemical cures for root rot so you’ll have to bag and bin affected plants.

Prevention is the only answer which means taking care to ensure that the potting soil is not too wet or dry.

7. Rust


The problem: Tiny rust colored nodules mainly appear on the undersides of leaves, which turn yellow and die. 

This fungal disease usually only affects outdoor garden plants but can affect pelargoniums grown indoors.

Solution: Avoid over feeding which can increase the chances of infection. Remove affected leaves as soon as you see them. There are no chemical cures for rust.

8. Sooty Mold

Problem: Sap sucking pests such as aphids produce a sugar rich honeydew which can result in a black or dark brown fungal growth appearing mainly on the leaves.

Solution: Remove the pests if possible, see here, and wipe off the fungus with warm water. This is no chemical cure for sooty mold.

9. Stem & Crown Rot

Problem: You’ll first notice this fungal disease as stems turn black or brown around the soil line and this discoloration can travel upwards towards the leaves.

The plant will begin to wilt and then show signs of decay.

Solution: Unfortunately, there is no chemical cure for stem and crown rot and often, by the time you detect the symptoms of this disease, it’s too late to save the plant.

Again, the best solution here is prevention, by ensuring that your soil is well drained and not soggy.



Problem: Virus shows itself as pale green or yellow spots, streaks, mosaic like patterns or rings on leaves.

The flowers may also show white or pale streaks and growth of the plant may be stunted or distorted.

Solution: Prevent spread by bagging and binning affected plants. Avoid propagating a plant with suspected virus. There is no chemical cure for virus.

Final Thoughts

Regular inspection of your indoor plants may result in early detection of diseases and possible remedy.

However, as there is no chemical cure for many of the most common indoor plant diseases, prevention is by far the best solution.

Make sure not to over water or under water your plants and keep them in well drained pots with holes underneath.

Also, don’t kill your plants with kindness by over feeding them and keep them in a well-ventilated position.

Christine Mattner

What started out as purely a desire to keep my indoor plants alive has turned into a full-blown passion for sharing what I have learned over the years about selecting, growing and caring for indoor plants with those who may be new to the wonderful world of houseplants.

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