11 Common Houseplant Diseases and How to Treat Them

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Houseplants beautify your home and bring a little bit of nature indoors. The bad news is that there are many common houseplant diseases that can infect them, make that beauty unattractive, or even kill them.

Many people associate plant diseases with outdoor plants, but indoor plants also suffer from diseases. Your houseplants can also contract pests.

If you are wondering what types of houseplant diseases you can get, here is a list of the most common ones. Remember, good preventive garden practices go a long way in preventing houseplant diseases.

11 Common Houseplant Diseases

Using the proper preventative measures to stop houseplant diseases in their tracks is one of the first things you need to pay attention to. Make sure you avoid overwatering and never leave plant debris on the soil. Thin out any plants that are overgrown and overcrowded. Ensure proper air circulation by opening windows or using a fan.

You’d be surprised how easy it is to avoid indoor plant diseases!

1. Anthracnose

Anthracnose is a soil-borne fungal disease that infects a range of plants, including houseplants. Outdoors, the disease is difficult to get rid of because the spores winter on leaves and branches. Then, when warmer conditions arrive, the spores become alive.

Inside, where it doesn’t get cold enough to slow down or kill the pathogen, disease can actually spread. So you need to be careful.

Anthracnose appears on your plants for a number of reasons, such as:

  • reuse of infected soil
  • allowing dead plant debris to remain on the soil
  • Inappropriate cultural conditions such as wet soil or overcrowding

The common sign of anthracnose is yellowing of the leaf tips. The yellow areas darken, turn brown and eventually die. You may notice discoloration happening around the outer edges of the leaf.

Check out our guide to anthracnose in the garden for tips on controlling this disease, as the treatment is the same. Just be aware that some fungicides are not approved for use indoors.

2. Bacterial Leaf Spot

Bacterial leaf spot is one of the more serious houseplant diseases you may encounter. This often leads to the death of your plant, and various bacteria cause the disease. This means that it can have different symptoms depending on the bacteria causing it.

Sometimes, bacterial leaf spot is localized and affects only the foliage. Other times, it is systemic and travels throughout the plant. It can also appear as black, water-soaked sores that have a yellow pattern around them.

You can learn more about bacterial leaf spot in our guide.

3. Cercospora

If you notice yellow spots on the underside of leaves on your houseplants that eventually make their way to the top of the plant, your plants may have Cercospora. Over time, the yellow spots enlarge and become purplish-brown as the leaves become sunken.

Cercospora eventually causes leaf loss with infection closer to the node. This disease is usually caused by poor air circulation and too much moisture on the leaves.

The bad thing about Cercospora is that no fungicide helps get rid of the disease. You need to use other methods to control it before it kills your entire plant.

First, cut off any infected leaves or flowers. Again, be sure to water only at soil level, not over the leaves. If you can, you can also prune your plants to improve air circulation.

Lastly, if you can’t get past the problem, try removing the plant from its pot and washing away all the soil from the roots. Clean the pot with a 1:10 bleach to water mixture and reapply with fresh, clean soil.

4. Fungal Leaf Spot

Houseplants can suffer from fungal leaf spots caused by various fungi, but thankfully, preventive measures and treatments work to get rid of many of these diseases. Fungal leaf spots are common when the potting mix is ​​consistently wet, and the foliage remains wet for a long period of time.

The disease appears on the foliage of your houseplants in different colors, such as brown, black, red, yellow, or tan. It also causes leaf drop and deformity.

Removing infected leaves and fallen debris is one way to prevent the spread of the disease. Fungicide sprays can kill the fungus on your plants, but be sure to use a type that is approved for indoor use.

5. Gray mold

Gray mold is known as botrytis blight, and is one of the most common houseplant diseases. It is a fungal disease that is a serious issue – it easily kills infected plants.

Gray mold survives on dead plant debris, so unless it is cleaned up, this fungus spreads easily. In addition, the spores are released into the air, infecting other nearby houseplants. The spores are also transferred to the foliage via splashes of water on the plant.

How do you know if your plants have gray mold?

The disease prefers flowering plants, killing them before the flowers open. This causes the gray, bull’s-eye pattern to develop cankers on the stems along with the older foliage. You will also see a thick, gray mold covering the dead plant debris.

Treating gray mold is possible, especially with appropriate environmental changes. It’s important to treat it as soon as possible to avoid spreading it to other plants in your house. Prune the plants to improve air circulation and consider using a room fan until the disease is under control.

Consider adding water and a houseplant mulch at the base of your plants. Internal use fungicide can be used in severe conditions.

6. Powdery Mildew

Most gardeners have heard of powdery mildew. Not only is it one of the most common garden diseases, but it also infects a lot of indoor plants. Powdery mildew is a fungal disease that occurs on houseplants in the winter months when indoor temperatures are cool and humidity is high.

Usually, powdery mildew does not kill houseplants, but it is unattractive and the spores can travel in the air and infect other plants. The problem is fairly easy to diagnose; You will see white, powder-like circles on the leaves that enlarge and spread.

If houseplants contract powdery mildew, it is usually a sign that cultural changes need to be made. Learn more about powdery mildew by reading our guide. Neem oil and copper fungicide are good treatment options.

7. Root and Stem Rot

One of the chronic problems with over-watering houseplants and poorly drained soil is soil. Well-meaning plant lovers sometimes water daily, thinking they are doing the best job, but over-watering leads to root and stem rot.

Root and stem rot is caused by various fungal organisms. These pathogens live in soil that has poor drainage and is wet at all times.

Root and stem rot is a little difficult to spot because the main symptom is that the roots are pulpy and black, but you can see the roots only when you remove the plant from the container. Another symptom is that the plant will wither from the bottom up as the leaves and stems turn brown or black.

Unfortunately, dealing with root and stem rot is difficult, if not impossible. In most cases, taking the plant outside is the best way to handle it.

If you want to try to save your plant, remove it from the pot and wash away all the soil. Wipe down the container with a 1:10 bleach and water mixture. Dust the roots with copper fungicide powder. Then, repot with fresh potting soil. Be extra cautious to water appropriately.

You may want to grab a moisture meter to help you know when it’s time to water.

8. Rust

Rust is more common on the outside than on the inside. It is most common on roses, fuchsias and chrysanthemums, so if you grow them as houseplants, be careful because rust is a particularly harmful infestation.

Here’s how to get rust off your houseplants.

Look for brown rings or spots on the leaves. These spots usually start on the underside of the leaves, but advanced stages of rust appear on both sides. Over time, the leaves drop from the plant prematurely without any yellowing.

Dealing with rust on your plants is challenging; Regular use of copper fungicide cannot control it, if not get rid of it. Here’s what you need to know about rust on your plants.

9. Southern Blight

While southern blight is not as common as other houseplant diseases, it is still a problem you may encounter. Due to this disease, the lower leaves of your plant die quickly along with root rot.

At first, you may notice parts of your plant turning a mushy look with a creamy yellow and, eventually, brown. Sometimes, a white fungal growth appears on the stems of plants when there is too much moisture in the environment due to poor air circulation.

One way to help slow the spread of the disease is to remove the affected leaves and discard them. Then, try to improve the air circulation in your home. Unfortunately, fungicides and other specific treatment options for fungal diseases will not work for southern blight.

10. Sooty Mold

Sooty mold is most common on outdoor plants, but it is also possible for these fungi to infect houseplants. If you find that you have sooty mold on your plants, it means you have another problem – pests.

Sooty mold usually occurs when your plants have honeydew that comes from various pests on your plants. Some common insects that secrete honeydew include:

  • aphids
  • mealybugs
  • white fly
  • leafhoppers

Thankfully, in most cases, sooty mold is just an annoying look on your plant rather than a serious problem. The real problem is the pests that cause honeydew and attract sooty mold. This is what you need the most treatment for.

When you’ve got the pests under control, clean your plants with a little dish soap mixed with water.

11. White mold

Houseplants commonly contract white mold, which is a white moldy substance that grows on top of potting mix. While white mold won’t kill your plants, it is ugly, and no one wants that on their plants!

What causes white mildew?

Poor cultural conditions are the usual culprit behind white mold, but it’s usually an easy solution. White fungus growing on your potting mix is ​​a sign that the growing conditions are not right, and can lead to more serious problems.

Some causes of white mold include:

  • fill more water
  • growing in an already infected potting mix
  • improper drainage

You can remove white mold from the top of the soil, but you’ll need to change your growing practices to keep it from coming back.

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