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Monsteras are stunning houseplants known for their attractive foliage. While they are relatively easy to care for, Monsteras are not immune to problems and diseases which can threaten the health and appearance of the plant. One such problem is bacterial leaf spot.

Bacterial leaf spot on Monstera is a common disease that affects this plant. Knowing what to look for, as well as how to treat and prevent the problem, is vital to ensure your Monstera lives a long and healthy life.

bacterial leaf spot on a Monstera leaf

Signs of bacterial leaf spot on Monstera

Knowing the signs of bacterial leaf spot on Monstera can help you quickly identify the problem.

1. Dark spots on leaves

The most common symptom of bacterial leaf spot is dark spots peppering the monstera leaves. These spots typically appear as the first sign that something is wrong with the Monstera.

2. Spots with yellow halos

Some of the spots you see may appear brown in color with a yellow halo.

3. Spots range in size

The spots that occur are irregular and have a width of about 3/16-inch to 1/2-inch. The spots can be either circular or more irregular in shape.

4. Water-soaked spots

You may also see spots appearing on the leaves that are water-soaked, though these typically occur on older leaves.

5. Leaf collapse

Once the disease progresses, the affected leaves will collapse. You may see a few or several diseased leaves littering the top of the Monstera’s soil. Make sure to remove and discard these leaves as soon as possible.

6. Dry and papery spots

Older spots will start to dry and develop a papery-like texture. Even when they become dry, the spots will still have a dark brown, black, or reddish color to them.

7. Discoloration of the leaves’ edges

You may also notice the edges of your leaves appear discolored. This usually occurs after the spots have appeared on the leaves.

8. Oozy leaf spots

The spots that appear on the leaves may begin to ooze a sticky bacterial substance. This may or may not occur, and when it does, it can appear on both old and new spots.

9. Leaf spots run together

When the plant is subjected to overly wet conditions, the leaf spots can start to enlarge and run together. This can result in large portions of the leaves appearing as one big spot.

10. Unpleasant odor

Bacterial leaf spots can cause the Monstera to smell unpleasant. As the disease progresses, the plant will give off an odor that may smell musty or like rotting leaves.

How do you treat bacterial leaf spots on Monstera?

Because there are no effective chemical treatments for bacterial leaf spots on Monstera, gardeners are left using mechanical control options to treat the disease.

1. Reduce watering

Overwatering is one of the most common causes of bacterial and fungal problems, such as bacterial leaf spots. If you notice this disease on your Monstera, reduce the amount of water you give the plant. Make sure to only water the plant when the top few inches of soil feels dry.

2. Reduce the humidity level

Humidity is another thing that can aggravate and cause bacterial leaf spot on your Monstera to get worse. Reducing the humidity level will go a long way to helping the plant recover from this disease. 

One way to reduce humidity is to remove any pebble trays you may have the pot sitting on, or you can use a dehumidifier to pull the water from the air.

3. Increase airflow

Good airflow is needed to keep the leaves of the Monstera dry and free of diseases. If you have the plant too close to other plants, you will need to move the Monstera to another location where it isn’t too crowded. Remember, the air needs to flow through the plant and reach the surface of all the leaves.

4. Prune infected leaves

Remove and discard infected leaves. Keep in mind, however, that you shouldn’t overly prune the plant, since removing all or majority of the leaves isn’t good for the Monstera. 

A good general rule of thumb is that, if more than one-third of the plant is infected, prune the plant over a period of time and not all at once.

5. Isolate the plant

Keep the infected plant away from other plants to help stop the spread of bacterial leaf spots. Furthermore, refrain from overly touching the plant and always sanitize pruning shears after using them on the diseased Monstera.

6. Apply copper fungicide

Chemical treatments are not effective once the disease sets in. If, however, you spot the problem early enough, you might be able to control the bacterial leaf spot with copper fungicide. Make sure to follow the application instructions found on the fungicide’s label.

How to prevent bacterial leaf spot on Monstera

Once bacterial leaf spot attacks the Monstera, it can be difficult to get rid of. That is why it is better to prevent bacterial leaf spot before it has a chance to take hold of your plant.

1. Avoid overwatering

Overwatering plants is one of the quickest ways to ensure they experience bacterial and fungal problems. To help keep your Monstera healthy, only water when the soil begins to feel dry. 

To test the soil, insert your finger about 2 inches deep into the soil. If it feels damp, wait a day or two and test the soil moisture again.

2. Properly care for the Monstera

Providing the monster with the ideal growing conditions will go a long way to keeping the plant happy and healthy. This also prevents bacterial leaf spot from occurring. 

Furthermore, if the Monstera does experience an issue, they are more likely to recover quickly if they are strong and healthy from the start.

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Specially designed soil for your Monstera. Light and well-draining, making it perfect for avoiding root rot, while being packed with just the right nutrients to keep your plant happy.

3. Don’t overcrowd the plant

When plants are placed too close together, it can block the air from flowing freely through the plant. Without good airflow, any moisture that appears on the leaves of the Monstera won’t dry properly, which increases the chance of diseases, such as bacterial leaf spot.

4. Remove any fallen leaf debris

Leaf debris that is left to sit on the top of the Monstera’s soil can quickly become a host for pests and problems. Not only does it increase the chance of the plant developing bacterial leaf spot, but it also encourages rot, insects, and various other fungal problems.

What’s the difference between fungal leaf spot on Monstera and bacterial leaf spot?

Leaf spots on monstera can be caused by either bacteria or fungus. Both types of leaf spots look similar and can be hard to distinguish between the two. The good news, however, is that both fungal and bacterial leaf spots have the same treatment and prevention measures.

It is extremely difficult to tell the difference between fungal and bacterial spot on Monstera. In fact, it is so difficult that most gardeners don’t even bother trying to determine whether it is a fungus or a bacteria causing the problem. Instead, they act fast and treat the issue. This is because both fungal and bacterial leaf spots require the same treatment and even have the same preventive measures.

The most important thing is to quickly spring into action to control the leaf spots before they take their toll on your Monstera. Once you have the issue under control, take the necessary preventive maintenance steps to keep the spots from returning.

Some of the main differences in fungal leaf spot vs bacterial leaf spot on Monstera are outlined below.

1. Appearance of spots

Bacterial leaf spots tend to have a more angular appearance compared to fungal leaf spots. However, this isn’t a hard and fast rule.

2. Yellow halo around spots

Bacterial leaf spots may also have a yellow halo around them. But not all spots caused by bacteria have that halo and many can appear without it.

3. Soft rot can occur on the leaves

Sometimes, bacterial leaf spots will cause the leaves to develop soft rot. This can occur at the tip of the leaf and extend upward, or it can appear in the middle of the leaf. Unfortunately, there are also some fungal pathogens that can cause the same type of soft rot.