To keep your houseplants beautiful and thriving, you’ll need to know what you might need to fend off. You’ll find that, with most houseplant diseases, prevention is key! There are some effective ways to treat certain plant diseases as well. Learn how to identify and treat the most common diseases to ensure your plants will live long and healthy lives!

1. Root Rot

Root rot - identification and treatment

What Does Root Rot Look Like?

As with stem and crown rot, root rot is not outwardly apparent until the later stages. It attacks the roots directly, wreaking havoc under the surface. If you think a houseplant may have root rot, gently unpot it and check the roots. Infected roots will eventually turn soft, shriveled, and dark. In contrast, healthy roots are usually light in color and are always quite firm. As root rot progresses, the leaves will wilt, turn yellow, and fall off.

What Causes Root Rot?

Unfortunately, root rot is quite common. It is a hardy fungal disease that loves warm, damp potting soil. It’s also highly infectious to other plants. In order for the fungus to thrive, it must have an excessively wet environment, typically caused by overwatering or poor drainage.

How Can You Treat Root Rot?

When a houseplant acquires root rot, it’s nearly impossible to get rid of. If there are any healthy roots remaining, you can try salvaging those while removing the rest. You’ll also need to apply fungicide, and use a new clean pot (or bleach the current one) and fresh, untainted soil. There’s a good chance that the rot will stick around and spread regardless, but your plant could be a lucky survivor. Who knows?

How Can You Prevent Root Rot?

Root rot is one of the most devastating diseases a plant can acquire. It has a very high fatality rate and it’s rare that a plant will recover. With this in mind, prevention is more important than ever for this disease. 

Always ensure that your houseplants have soil that drains properly and that their pots have drainage holes in the bottom. Also, use care not to accidentally overwater your plants. In fact, it’s generally much safer to err on the side of underwatering than overwatering (though a balance is ideal).

2. Powdery Mildew

Powdery mildew - identification and treatment

What Does Powdery Mildew Look Like?

Powdery mildew is a fungal disease that is easy to identify. Afflicted plants look as if they have been dusted in powdered sugar. Powdery mildew starts out in circular spots that can appear on any part of the plant, but it usually shows on the upper parts of leaves.

What Causes Powdery Mildew?

Powdery mildew likes a unique combination of shade and warm, dry conditions. It’s a fungal disease that can seem to appear randomly.

How Can You Treat Powdery Mildew?

Powdery mildew disease is best treated with fungicides. It is recommended to spray any affected plants down with fungicide, including neem oil and lime-sulfur. If you’d prefer a more natural option, baking soda can also do the trick. Just mix roughly 1 tsp of baking soda with 1 quart of water.

How Can You Prevent Powdery Mildew?

Powdery mildew is most effectively prevented by providing plenty of sunlight. Air circulation is also important, so don’t let any debris collect around your plants. Just these two things will go a long way to preventing powdery mildew!

3. Plant Rust

Plant rust - identification and treatment

What Does Plant Rust Look Like?

Plant rust has earned its name for its distinctive appearance: that of rust. It manifests in the form of dusty orange patches that look like rust on metal. Like rust, it’s also spread by water. But unlike rust, it’s a living fungal disease. It will release spores once it attaches itself.

What Causes Plant Rust?

Like many, if not all fungal diseases, plant rust does best in damp conditions with poor airflow. Overhead watering will encourage plant rust, as will poorly-draining soil.

How Can You Treat Plant Rust?

Plant rust disease is not usually deadly, but it will affect the beauty and growth of your houseplants. If your plants are having trouble with rust, remove as many of the affected parts as you can, and then apply a copper spray or sulfur powder. 

How Can You Prevent Plant Rust?

Avoid getting your houseplants’ leaves wet to help fend off rust. Additionally, ensure that your plants are spaced with enough airflow, and remove any dead leaves or other detritus that might accumulate around your plants. 

4. Sooty Mold

Sooty mold - identification and treatment

What Does Sooty Mold Look Like?

Sooty mold is very distinctive and easy to identify. As its name implies, it looks like soot or ash. It forms a fine black powder. While this disease is not directly harmful to plants, it interferes with photosynthesis and can prove deadly if left untreated. Most also consider it unsightly and therefore doubly undesirable.

What Causes Sooty Mold in Plants?

Sooty Mold has a rather unique cause: pests. Or, more specifically, the fungal disease forms on the honeydew secretion that pests leave behind. Ladybugs and thrips are two of the biggest culprits.

How Can You Treat Sooty Mold?

To get rid of sooty mold, you’ll have to first eliminate the pests. You can also treat the present mold with fungicides and remove leaves that are blighted beyond repair. Sooty mold tends to stick to plants stubbornly, but some success can be had in removing it with a mixture of 1 TBSP household detergent and 1 gallon of water. Apply it, leave it on for 15 minutes, and then rinse well. Repeat this a few times over the next few weeks if necessary.

How Can You Prevent Sooty Mold?

The best way to prevent sooty mold in houseplants is to consistently fend off any pests. This should nip the situation in the bud.

5. Plant Viruses

Plant viruses - identification and treatment

What Do Plant Viruses Look Like?

Plant viruses usually manifest in the form of leaf yellowing. This will often appear in the form of blotches and stripes and sometimes as flower and fruit abnormalities. You can also keep an eye out for the stunting of growth and distortion (misshapen fruits and leaves). Symptoms of viruses in plants are not always apparent, however. 

What Causes Plant Viruses?

Insects are the carriers, typically. Hoppers, thrips, whiteflies, aphids, mites. Naturally, plants are highly resistant to viruses. In order for them to contract one, something must introduce the virus to them (also known as a vector).
The most common cause is pests. These both carry viruses and wound the plants to allow them in.

How Can You Treat Plant Viruses?

Get rid of the source of the virus, AKA the ‘vector.’ This means standard pest treatment. Infected plants are extremely difficult to cure, so quarantining them is best. Infected plants should be quarantined or thrown away and never mulched or composted. Viruses are both highly infectious and extremely difficult to get rid of. If you’re determined to try to save an infected plant, quarantining it and treating the pests is sometimes successful.

How Can You Prevent Plant Viruses?

Because plant viruses are so hard to kick, prevention is more important than ever. Spray for pests regularly, and sanitize your tools when pruning your plants. You can also opt for virus-resistant plant varieties.

6. White Mold

White mold - identification and treatment

What Does White Mold Look Like?

At first, you may think that white mold and powdery mildew look similar. Its appearance is actually quite distinct if you look closer. White mold grows in fuzzy spots that spread, whereas powdery mold powders the surface like flour. Eventually, the mold can take the entire plant over. It’s not typically deadly, but it will cause the health and beauty of your plants to suffer.

What Causes White Mold?

White Mold loves warm, damp conditions, as well as dim lighting. Weeds can also carry it.

How Can You Treat White Mold?

The best treatment for white mold is a combination of water, baking soda, and dish soap. Milk spray can nip it in the bud, and you can also try fungicides or Neem oil.

How Can You Prevent White Mold?

To prevent white mold, ensure that your houseplants have properly-draining soil. Additionally, avoid watering the tops of your plants, as the wet leaf surface is prime territory for white mold growth. Finally, take care not to overwater!

7. Crown and Stem Rot 

Crown and stem rot - identification and treatment

What Does Crown and Stem Rot Look Like?

Once the signs of crown and stem rot become apparent, it’s probably too late for the afflicted plant. This fungal disease takes hold quickly and infects the entirety of the plant above the soil (sometimes it is also accompanied by root rot below).

So, what does it look like? Plants with root rot will gradually begin to discolor, turning red, brown, and black. This is a sure sign that the affected tissue is dying off.
As crown and stem rot progresses, the leaves will wilt and wither. Bit by bit, the entirety of the plant will die off.

What Causes Stem and Crown Rot?

Crown and stem rot is especially common in herbaceous and woody ornamental plants. It’s a humidity-loving fungus that lives comfortably in the soil. The primary cause of crown and stem rot is poorly-draining soil. 

Additionally, nutrient deficiency can make the plant more vulnerable to crown and stem rot. The rot typically enters plants through any wounds they might have (from pruning, repotting, or whatever else).

How Can You Treat Crown and Stem Rot?

With this particular disease, the chances are slim that your plant will recover. If you’re determined to try, start by removing any afflicted parts of the plant that you can see. Next, apply fungicide, and repot the plant in a new, clean container and entirely new soil. Otherwise, the rot residing in the old soil and pot will simply transfer over!

How Can You Prevent It?

Perhaps more than with any disease, prevention of crown and stem rot is vital to your plants’ survival. How? The most important step is to ensure that the soil drains well. Next, try to water the soil directly instead of getting the leaves or stems wet. Finally, sanitize your implements (such as an Exacto knife) properly before pruning, and keep your plants strong with nutrient-rich soil and fertilizer. 

8. Gray Mold (Botrytis)

Gray mold - identification and treatment

What Does Gray Mold Look Like?

Gray mold is one of the easiest plant diseases to identify. It’s a fuzzy gray mold that appears on leaves as small white holes that gradually grow. As it grows, it blights the leaves, fruit, buds, and flowers – causing them to turn brown and then black. The brown holes that appear will often look like targets. As the disease progresses, the afflicted parts of the plant will wither and die off. 

What Causes Gray Mold?

Gray mold generally attacks weakened plants, or those with fresh wounds from pruning, repotting, or the unfortunate placement of someone’s foot. Poor circulation and excessive dampness are the other two main culprits. So, what can you do about it?

How Can You Treat Gray Mold?

Fortunately, gray mold is not as fatal as some other diseases that plants might acquire. With drier conditions and better circulation, it is possible to fight it off. If you have an especially bad case of gray mold, you can apply fungicide or neem oil.

How Can You Prevent Gray Mold?

If you’re having trouble with gray mold, or if you’d like to prevent it, avoid overhead watering. This causes the leaves to become damp, which creates the ideal conditions for gray mold. Instead, irrigation or a ground hose is considerably better! Or, for houseplants, try to water the soil directly instead of getting the leaves or stems wet.
Additionally, plants should be spaced appropriately, and debris should be prevented from accumulating between them (dead detritus such as this is the perfect gray mold breeding ground).

9. Nutrient Deficiency

Nutrient deficiency - identification and treatment

What Does Nutrient Deficiency Look Like?

General signs of nutrient deficiency are yellow leaves and poor flowering. More specifically, nitrogen-deficient leaves may display leaf yellowing or browning, as nitrogen is a large part of what keeps plants green and leafy. 

A lack of potassium, on the other hand, is often indicated by yellow or purple leaf tints and poor flowering. If a plant is displaying slow growth and dull yellow leaves, it may be lacking magnesium. The leaves may also turn red and begin to fall off. 

What Causes Nutrient Deficiency in Plants?

There are many causes of nutrient deficiency in plants, the primary ones being overly-dry soil, sandy soil, and improper pH (such as very acidic or alkaline soil). The over-use of high-potassium fertilizers is also a known cause (though the proper amount is still necessary).

How Can You Treat Nutrient Deficiency?

Short-term, you can help your plants make a quick recovery with fertilizer. There are various types of fertilizer, and you may need to judge which is needed. Sometimes, multiple fertilizers are called for, including nitrogen-rich fertilizer and potassium-rich fertilizer. 

You can also keep your plants nourished and happy by occasionally giving them a healthy dose of compost and organic matter.

How Can You Prevent Nutrient Deficiency?

You can prevent nutrient deficiency in your plants by ensuring that their soil is the right kind, that they are watered with balance, and that the soil has the proper pH. There is a very good chance that, with care, your plants will recover.