Bacterial black leaf spot is a disease that affects Monstera plants. It is caused by the bacterium Xanthomonas campestris pv. malvacearum, which thrives in warm and humid conditions with low light exposure. This post will talk about what causes a bacterial black leaf spots on Monstera plants, how to prevent it from happening, and treatments for this plant pathogen.

Causes of Black Spots on Monstera Plants

The most common cause of black spots on Monstera plants is bacterial leaf spot, or Xanthomonas campestris pv. malveacearum. This disease thrives in warm and humid conditions with low light exposure, which can be caused by over-watering the plant, exposing it to outside environments too often, obstructing light by placing it in a dark room, or other environmental factors. The bacteria enter the plant through wounds on the plant’s leaves and stems, leading to black spots that will turn brown as they age.

The best way to prevent this disease is to keep your Monstera plants healthy by regularly watering them with clean water only when needed, giving them enough light, and keeping their environment clean.

Additional Causes To Look Out For

Can Root Rot Cause Black Spots on Monstera Plants?

Root rot can cause black spots on Monstera plants but is not a common cause. This disease appears as sunken brown patches in the soil that will spread if left untreated and eventually lead to the death of your plant.


Monstera plants are typically grown outdoors and can be quite sensitive to sunburn. This is because they have a thin cuticle layer that doesn’t protect the plant from burning in strong sunlight.

When leaves experience severe sun-related damage, black spots may appear on them as a result of bacterial invasion if the burn damages the leaf tissue enough for the bacteria to penetrate and feed on the dying plant cells. This is because it kills off healthy tissue, making them easy prey for infection.

The best way to prevent this from happening is by protecting your plants with a shade cloth or other means of shading in direct sunlight during peak hours (11 am-12 pm). In addition, water regularly and fertilize your plants for best results.


Black leaf spot on monstera plants is often caused by overwatering. One of the most common reasons why a plant falls victim to a black leaf spot, especially one that’s located near or in a greenhouse, is because it was watered too frequently while under humid conditions. If your leaves have been turning brown at their tips and edges for some time, and you also notice that your plant is drooping, it could be a sign of overwatering.

When watering monstera plants outside during the summer months, make sure to allow for proper drainage by creating some space between the potting soil and its saucer. This will allow for the water to soak in and not pool at the base. The soil should also be allowed to dry out a bit before watering again so that mildew is less likely to form as well.

If a black leaf spot has already begun to form on your monstera plant, it’s important to cut away the infected leaves and stems. Avoid watering your plant when you’re at home so that water doesn’t sit on its leaves for too long in between periods of being watered.


Watering too infrequently will also result in the appearance of black leaf spots on Monstera plants. In addition, overwatering and not watering enough can both cause dehydration, which leads to this disease as well.

If your plant has been sitting in a dry pot for some time with very little water left inside it, you’ll notice that the leaves will start to turn yellow. This is a sign that the plant needs more water, and in order to prevent black leaf spots from occurring, you’ll need to re-water it.

Physical Damage

Leaves on Monstera plants that have been damaged by physical means are susceptible to black leaf spots. This can be caused by other people or animals, such as cats and dogs.

The best way to avoid this is by keeping your plant in a safe area where it will not come into contact with these things. You may also want to consider using a repellant to keep these animals away.

Too Much Misting

Misting a Monstera plant is not recommended, as this can cause black leaf spots to form more quickly.

In the event that you’re in need of making your plant grow faster, there are better ways than misting it every few hours with water. Instead, try fertilizing or pruning away some of its leaves so that sunlight will be able to penetrate the leaves more easily.

Frost Damage

Frost damage can also lead to black leaf spots on Monstera plants. This is because the leaves will need time to heal, and if they’re constantly being damaged by frost over a long period of time, then it’s likely that bacteria would start inhabiting it as well.

To avoid this from happening again in the future, make sure that your plant is in a sheltered area to protect it from frost. You may also want to cover the leaves with straw or other material if you notice that they’re turning black, which could indicate that bacteria has already begun attacking them.

Mechanical Damage

Mechanical damage, such as ripping leaves off of a Monstera plant’s stem or trunk due to rough handling, also causes black leaf spots.

It can be difficult for a plant that has been injured in this way to heal on its own because the bacteria will have extra access to it and there is now an opening for infection. If you accidentally injure your plant in this manner, try to seal the wound with a product that will promote healing.

Cold Temperatures

Cold temperatures can cause black leaf spots on Monstera plants, and this is because there will be less water in the leaves.

During cold seasons, it’s important to make sure that your plant has access to plenty of warmth so that it doesn’t become too dry and develop a disease as a result.

You may also want to consider moving your plant indoors during the winter months so that it can receive more care and prevent damage from occurring.

Fungus or Pests on Monstera leaves

If your Monstera plant has a fungus or pest on its leaves, this can also lead to a black leaf spot.

The best way to prevent these things from happening is by making sure that you’re giving the plant enough water and nutrients so that it doesn’t have problems with diseases in general.

It’s also important for owners of plants to look out for pests, as this can lead to more problems.

You may want to try applying a pest spray on the leaves or using other methods like soapy water, diatomaceous earth, and neem oil in order to prevent these things from happening again.

Treatment for Bacterial Black Leaf Spot on Monstera Plants

If you already have black spots on your plants, there are a few things you can do to prevent them from spreading too far or worsening. Replace infected leaves with healthy ones to stop the spread of spores in the air and keep the plants healthy.

If the spots are on a large number of leaves, you can try removing some or all of them to prevent more from growing and replace them with clean ones if possible. The best treatment for bacterial black leaf spot is prevention as it is very difficult to remove once established in your Monstera plant’s environment!

Basic Caring for your Monstera Plants

Taking care of your Monstera plants is the best way to prevent them from developing black leaf spots. Be sure that you’re giving them enough water, nutrients, and love in order for it not to have any problems with diseases generally. You may also want to consider applying a pest spray on the leaves or using other methods like soapy water, diatomaceous earth, and neem oil to prevent pests from attacking your plants again.

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Last update on 2023-08-08 / Affiliate links / Images from Amazon Product Advertising API

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