Why Are Brown Spots on Begonia Leaves?

There is your vibrant begonia, in an end of the house. You are happy that the plant can make your life more cheerful and more peaceful, especially on rainy days.

Then, suddenly, you notice the horrible brown spots appearing within the leaves. You are a bit shocked and scared.

The next challenge is to find out the reason behind the brown spots to show up. Don’t worry about it as this article can assist you in determining the cause.

The reasons that could cause spots of brown appear on your leaf of the begonia could be due to excessive light, stress from temperature and pests, or diseases. Whatever the reason it is important to perform a series of steps to treat your begonia.

Continue reading and I’ll show you step-by-step the causes that lead to the development of those undesirable brown spots.

How to Identify Begonia Brown Spots?

The kind of brown spots that you notice on the begonia’s leaves are likely to provide clues to determine the probable reasons. This is a quick guide to figure the cause.

Then, find out the spots that have brown spots. Are they on the older leaves or on the younger ones? Are they in their middle leaf or at the tips or spread across the leaves?

Then, check out how big and the number of brown spots. Are they small or large? Are they a lot or only a handful?

Thirdly, look at the way they appear. Are they dry, water-soaked, or hard? What color is it? Are there rings and halos in the area?

These tips will allow you to determine the cause of why spots of brown appear on the leaves of your begonia. Through the simple observation of signs, you will be able to determine what the issue is.

Why Does My Begonia Have Brown Spots?

In general, the process of cultivating begonia is simple. It is a great choice for a range of climates and is able to endure even the most challenging conditions.

There are situations where your begonia becomes vulnerable and is susceptible to stress.

The stressors cause the plant to become weak. How do they cause that? Let’s get into an in-depth discussion of this part.

Here’s a list of most common reasons why brown spots show up on the leaves of your gorgeous begonia plant.

Excess Light

The requirement for light in begonias is contingent upon the type of subgroup your plant is part of.

It could be fibrous-rooted begonias that are rhizomatous and tuberous. They thrive in areas that have bright indirect light, semi-shade, or half-shade.

Since they are more familiar with shades Direct exposure to sunlight could be harmful.

The intense light intensity can cause damage to the leaves. In the end, leaves develop scorched spots on its surface, which are reflected in massive brown spots.

Scorches can appear not just in the middle of leaves, but also within the veins and margins. Sometimes, they can cause the entire leaf to fade, die, and then fall off.

How to Treat:

Move your plant to a place that is that is more shaded. If it’s outside your house and the light intensity is higher than normal take it inside.

If the window is near and the heat is radiating from the glass, place an opaque curtain between.

Another option is for you to remove your begonia from your window when the light becomes too strong and bright.

It is possible to return it when the lighting conditions become more bearable, like in the early morning or late afternoon.

This way, you’ll keep it from absorbing excessive light energy , which could cause damage to cells.

begonia plant in pot on ground

Pest Infestation

While pests aren’t too much of an issue for begonia however, being exposed to foreign species like whiteflies, Aphids, mealy bugs, spider mites, and weevils could harm the plant.

They’ll be apparent only after the brown spots appear in areas where they’ve created an appearance. (Sources: Clemson University)

Because they consume plant tissue by sucking sap, they typically leave tiny spots on the surface.

This is why you’ll notice those tiny brown spots scattered throughout the leaves.

How to Treat:

The most effective method of removing insects is to remove these from your begonia plants.

Of course, you need to be on guard in this regard because these microbes are small and almost unnoticeable to the naked eye.

A regular check of your begonia will aid in identifying insects at the beginning of their attack.

The application of water to them can also assist in getting rid of any unwanted visitors. Certain people use horticultural oils as well as insecticidal soaps to eliminate eggs and colonies. Most of the time pesticides are not required.

Temperature Stress

Begonia plants like a temperature that is within between 59 and the range of 79 to (oF (15 up to to 26C). It is not able to tolerate extreme cold temperatures because it isn’t frost-tolerant.

If your plant is exposed to abrupt and dramatic fluctuations in temperature, the chances that your leaves will begin to crystalize.

In the evening, when temperatures are too cold, the begonia leaves may freeze. As the day approaches and temperatures rise the leaves begin to thaw. This process can cause serious injury to the plant’s tissues.

How to Treat:

Protect your plants with insulation during periods of extreme cold. Utilize cotton sheets to prevent plants from freezing.

Be sure to keep them out of areas that are drafty, such as near fireplaces, air conditioners, windows that are windy, etc.


The cause of disease is a pathogen which can be bacteria or fungi. If your plant is infected by a specific fungus, it’ll show changes in its appearance.

A visible sign can be seen in the form of spots that appear brown on leaves.

It is reported that Penn State University lists seven diseases that could cause harm to begonia plants. The following are among them:

Bacterial Leaf Spot and Blight

The cause is Xanthomonas campestris pv. Begoniae. Brown spots appear to be water-soaked, with yellow bands around them. Infected leaves die one by one.

Botrytis Blight

Botrytis cinerea is the cause of this condition. The begonia’s leaves get a tan-colored appearance. This also causes the decay on the top.

Foliar Nematode

Foliar nematode disease manifests symptoms that include reddish, bronze-brown spots. The cause is an infection disease agent Aphelenchoides Fragariae.

Powdery Mildew

The cause of this disease is Oidium. The affected parts appear like powdery white due to the development of fungus. It is able to infect stems, leaves, and even flowers.

Pythium Rot

The petioles and stems from the plants die, and turn brown because of the Pythium. The leaves also begin to brown. Then, the entire plant will die.

Rhizoctonia Crown Rot

The pathogen responsible for this is Rhizoctonia,this disease can also cause the stem becoming rotten. The leaves turn brown and the whole plant dies.

Fungus’ presence can evident when the appearance of a white, powdery layer is seen in the dirt.


The virus causes severe chlorosis on the leaves of your begonia leaves. The leaves that are affected become deformed, and the plant is in a weakened state.

How to Treat:

Remove the affected parts from the plant. It is also essential to isolate the plant in order to avoid the spread of infection. The begonia should be placed in an area that is well ventilated and with a lower humidity.

Make sure that the plant does not get wet to prevent the development of the fungi. If the severity of the disease is very high, then you should consider applying fungicides to protect your begonia.

Rust Spots on Begonia

Another reason that brown spots develop on your begonia plant is due to the disease caused by the fungus called rust.

There are various kinds of rust, including canker rust, gall rust and leaf rust. They affect a variety of areas of the plant, including branches, twigs, leaves, and branches.

Rust spots first appear as small discolorations on the surface of the upper portion of leaves.

Then, it turns to a rusty hue. They are the spores that are spread across the lower parts on the leaf.

How to Treat:

Take off the infected leaves from your begonia. Reduce the moisture and make sure that the area in which it is placed dry. This will stop fungi from expanding and growing.

Fertilizer Problem

One of the dangers of fertilization overuse is the damage on the root system. The excess soluble salts in soil can increase the salinity of soil and reduce its pH. This makes nutrients and water less accessible to plants.

In this situation that the roots are compelled to put in a lot of effort to draw into these essential elements.

In the process, they suffer damage, often as a result of root rot and shrinking. Leaves of this plant change brown due to a deficiency of nutrients and water.

How to Treat:

Remove excess salts with water. The soil should be drained and allow it to rest for one hour. Then, pour the water to wash away any remaining salts.

Poor Air Circulation

A proper ventilation system is essential to ensure that plants thrive. The air moving around will always supply carbon dioxide, which is essential for plants to produce the food they need. Additionally, it will remove humid air from the surrounding area, preventing development of fungal growth.

If there’s adequate ventilation on hot days it can help lower the temperature inside your home.

It can help ease the strain caused by the rise in temperature.

Begonia plants that are placed in an area in which there isn’t enough airflow are more likely to contract diseases that are caused by pathogens. They also experience temperatures stress.


The windows in your house to let air flow through and out. You can also take your begonia outside for a couple of hours so that it can breathe in breath of fresh air.

In the event that you own an exhaust fan you can turn it on to draw out the air that is still inside the space.


Begonias love high humidity. Between 70 and 90% humidity within the atmosphere is required to ensure that the plant doesn’t get dry and die.

Dehydration can be caused by low humidity since the plant can quickly lose the moisture it holds.

However the humidity that is too high can encourage the development of pathogens. This increases the likelihood of plants developing illnesses.

There are two reasons that plants can get brown spots when the humidity isn’t ideal. One reason is that the leaves are prone to curland lose their moisture due to dehydration. Another is that it develops illnesses.


If your begonia suffers due to a low humidity A daily dose of misting can aid.

Be sure that you do this early in the morning to ensure that the droplets get enough time to evaporate before the end of the day. A humidifier can provide immediate solutions.

Improper Watering

Be careful when watering your begonia. The plant is susceptible to excessive watering, which is the cause of the death. If there’s too much water that the root begins to rot and causes impairment in functioning.

We are aware that plants that have rotten roots are afflicted by a shortage of nutrients and water.

Therefore, it’s not surprising to observe the leaves turning brown. These spots possess a slimy appearance and can smell horrible.

How to Treat:

If you think that watering too much is the cause, look at the begonia’s roots to determine how much damage has occurred.

If the portion that is rotten is not too severe, there is no need to repot. Simply remove the application of water until roots have fully recovered.

Let the soil completely dry before watering again. Take off dead parts of the plant.

For more details, check out my posts on how to repair an overwatered begonia.

Frost Damage

The final possible cause for brown spots on begonia could be frost damage. Be aware that begonias aren’t frost-tolerant, so when temperatures are very low, they’re more likely to suffer injuries.

The plant’s water tends to create crystals of ice. They disrupt the flow of fluids, causing the water and other metabolites to become unavailable to cells of the plant.

The areas that are damaged have spots of water that range from dark brown to black.

How to Treat:

Protect your plant’s begonia with cotton sheets to shield it from damage caused by frost.

This is particularly important in winter. It is essential to provide light above the plant to provide another source of heat.

How Do You Treat Brown Spots on Begonia?

Here are some suggestions for how to properly care for the begonia plants. In this way, you’ll reduce or eliminate completely the possibility of brown spots on the leaves.

  • Avoid Direct Exposure to Light

A bright light is essential for begonia , but remember not to touch directly. Be sure to shade your plants in summer, when the sun releases powerful light.

  • Watch Out for Drastic Temperature Changes

Temperature fluctuations are acceptable to plants, but extreme low or high temperature is harmful. This causes stress to plants, leaving the plants in shock, and in a state of not being able to adjust to sudden changes in the climate.

  • Treat Pests as Real Enemies

Pests can appear harmless, especially when they’re just a few in number. But, you shouldn’t take them lightly because they possess the potential to destroy beautiful begonias. Don’t wait for them become out of control before applying the appropriate treatment.

Most of the time pesticides aren’t required. Simply use mechanical methods to eliminate insects. If you are using chemicals, apply the DIY solutions that are made from soap and horticultural oils and dishwashing soap.

  • Be Prepared for Diseases

While your plant might appear healthy and well-established Don’t get complacent. The pathogens can suddenly surface once they have the chance. The reason for this is that the environment is favorable to their growth and reproduction.

Always make sure to use a sterilized soil in order to ensure that pathogens are eliminated. Select healthy plants to beginning. Remember to apply fungicides to prevent the spread of fungus.

  • Use Slow-Release, Organic Fertilizers

The buildup of salt is commonplace when you’re using fertilizers that are readily available. While they can make nutrients immediately available for plant intake, they also alter the pH of soil and salinity.

Instead of applying regular fertilizers that release quickly, choose organic options such as compost. It can improve soil’s texture and ensure the availability of vital fertilizers to plants.

  • Ensure Good Ventilation and High Humidity

A proper airflow and humidity will help the plant stay healthy. A high humidity level will aid in keeping the plant well-hydrated. Sprinkle mist on your plant when the humidity drops.

Your plant requires fresh air, therefore, make it a routine to open the windows in your house. There is a slim chance that diseases will be able to develop without adequate air circulation.

  • Regulate the Watering of Your Begonia

Overwatering is a frequent issue in begonia, so ensure that you water as necessary. The soil should be moist, but not overly wet. Get rid of stagnant water in containers and coasters, then make sure there is adequate drainage.

Make sure you use high-quality water and also. Be cautious with tap water as it could have high levels of fluorine and chlorine. They can also harm the plant.

  • Prepare for the Winter Season

Get out the blankets and cotton sheets to shield your plants. Incorporate additional light to create a more comfortable environment within your home. Reduce the amount of water you need during cold season.

There could be a number of causes for the brown spots that appear on your begonia. The majority of the time it’s a combination of the above factors.

If the environmental conditions are undesirable, plants experience stress, which weakens its immune system’ in the same way that humans do.

To avoid such issues try to ensure that your plant is growing in the best conditions. This will allow your plant to increase its strength and endurance against stress and diseases.



Went from a bad gardener to a half-decent one over 10+ years. Super happy to share my tips and tricks with you :)