Brown Spots on Alocasia Leaves (Causes And How to Treat)


Alocasia, commonly known as the elephant ear is a tropical plant with beautiful large leaves and zebra-like stems. Since it is a tropical plant, Alocasia thrives in a humid environment. 

So, have you realized that leaves in your Alocasia plant have brown spots and wondering what caused it and what to do to eliminate them? If yes, count yourself lucky because you have landed in the right place.

The most common cause of brown spots on alocasia leaves is fungal diseases and pest infestation. Overwatering, low humidity, temperature stress make the plant vulnerable to diseases and pests. Besides exposure to excess light and fertilizer can also cause the alocasia leaves to develop brown spots. 

Brown spot in Alocasia is caused by many reasons, most of which are preventable and even correctable.

In this post, I will discuss the most common reasons why Alocasia leaves get brown spots and how to treat them.

In this article I will discuss each possible cause and how to treat them effectively.

Causes Of Brown Spots On Alocasia Leaves

Brown spots in Alocasia may be caused by many factors. In this section, I am going to discuss the possible reasons why your Alocasia leaves have brown spots and how to treat each problem.

1. Low humidity

Alocasia plant is a tropical plant, meaning that it thrives in a humid environment. If it gets too dry, then it is more likely to develop brown spots. 

So, if you notice brown spots on your Alocasia plant, especially during the winter season, the most likely cause is low humidity.

During the winter season, humidity levels usually drop because cool air holds fewer moisture than warm air. 

If your home uses a forced heating system, the problem will even be worse because furnaces use combustion to create hot air, which burns out most of the water vapor present in the house.

As a result, your Alocasia plant is more likely to develop brown spots during the winter months.

How to Treat

The good news that is the problem can be fixed by increasing humidity around the plant.

There are many ways to raise the humidity around the Alocasia plant as discussed below.

One of the most effective ways of raising humidity around the plant is by misting the plant as often as you can.

Misting the plant will expose the soil and leaves to water particles that will evaporate, thus raising humidity around the plant.

Another great way to raise the humidity around the Alocasia plant is by putting cups, bowls, or any other container around the plant.

The goal here is to expose air to water. Water will evaporate thus raising humidity levels around the plant.

Another quick but effective method of raising humidity around the plant is by using a humidifier.

Besides keeping your house to a certain humidity level during the winter season, the humidifier can also create a humid environment for your Alocasia plant.

You can also use a pebble tray to increase humidity, add enough water to cover the pebbles, then place your Alocasia plant on the tray.

The pebble will hold the plant above the water, thus preventing the root from getting wet. Moisture around the plant will increase as water in the tray evaporates.

2. Rust

This is a fungal disease that affects all types of plants, including Alocasias. Rust is caused by a lack of sunlight, high humidity, and warmth. 

Once the disease has set in, a sudden increase in warmth can make it progress further, leading to more brown spots on the Alocasia leaves. If the problem is not treated on time it will kill off the leaves.

The first sign of rust on Alocasia leaves are tiny spots on the Alocasia that range in color, from rusty brown and red to orange. If left untreated, the spots will get bigger and turn into bumpy looking pustules.

The rust on your Alocasia leaves is usually not fatal but it can compromise the plant’s health. Additionally, it usually gets worse with time, meaning that if you don’t treat it on time, then it will spread to other parts of the plant, leading to stunted growth.

How to Treat

Rust in Alocasia mainly thrives in damp conditions. Therefore, it is recommended that you avoid overwatering your Alocasia plant. Instead, use drip irrigation or a soaker hose to keep water off the foliage.

Proper spacing of pallets can also help to prevent rust. Therefore, when planting the Alocasia, ensure they are well spaced to promote good air circulation.

It usually spread fast. So, when you notice that some leaves on the plant have been affected, prune or pick them immediately to prevent the disease from spreading.

However, this trick only works if only a small number of leaves are affected.

If there is too much moisture around the plant, regulate it using a dehumidifier. Lowering humidity around the plant to recommended levels will help to prevent the disease from spreading. Always water in the morning to allow the plant to dry out before the sunsets.

3. Excess Light

Alocasia is tropical, meaning that it does not perform well when exposed to sunlight for an extended period. 

Light is one of the most crucial factors needed for the growth and wellbeing of your Alocasia plant. This crucial energy is needed by the plant to grow, bloom, and produce healthy seeds.

However, too much sunlight is harmful for alocasia because it creates potentially damaging free radicals that may absorb too much energy than what the plant can handle, thus generating reactive species of oxygen that could destroy the plant.

If your Alocasia plant is exposed to too much sunlight, it may become beached, scorched, and limb, leading to the appearance of brown spots. 

Signs that your Alocasia plant is exposed to too much light include the presence of yellow leaves, even pale leaves, and brown spots on the tip of the leaves.

How to Treat

The solution to this problem is lowering plant exposure of light to the recommended level. For instance, if the plant usually sits next to the window where there is too much light, then it is advised that you move it away to a place where there is less exposure to sunlight.

You can also take the plant away from direct sunlight so that it only gets indirect light that is not damaging. 

Besides light exposure, light intensity also matters a lot. For instance, if your Alocasia plant was okay facing the west side window during the winter season, the same will not apply during the summer season. 

Light intensity varies according to seasons. This means that light intensity in the west-facing window during winter months is different from sun intensity during the summer months. 

It is recommended that you move your Alocasia plant to different parts of the house, depending on light intensity to prevent scotching.

Remember that light damage cannot be undone. So, ensure that you take quick action as soon as you notice the presence of scotch damage on the leaves.

4. Mildew

Like mildew that attacks homes, mildew on your Alocasia is a fungal disease, caused by high humidity levels. 

Mildew can slow down the growth of your Alocasia plant and if the infection is severe enough, the plant may die. 

There are two types of mildew, including powdery mildew and downy mildew. Downy mildew occurs in cold and humid conditions while powdery mildew occurs when the plant’s soil is too dry.

Powdery mildew is the most common type of mildew that attacks the Alocasia plant. It usually starts as a white spot on the leaves, but eventually, turns to brown spots if the plant is not treated on time.

Powdery mildew can leach important nutrients from the plant, causing the leaves to yellow and wither. 

Additionally, if most parts of the leaves become covered with the mildew, it will affect the process of photosynthesis and with time, the affected leave will fall off from the plant prematurely.

How to Treat

The best way to prevent powdery mildew from attacking your Alocasia plant is by keeping the soil in optimal condition. This means ensuring that the soil is not too dry or too wet. 

During the winter season, water the plant early in the morning, to give it enough time to dry before the day ends. Likewise, during the summer season, water the plant to prevent the soil from drying.

5. Pest attack

Pests also cause brown spots on Alocasia. Pests such as mealybugs can cause massive damage to the leaves, leaving brown spots throughout the leaf. This type of pest is common in houseplants and usually destroys everything, from leaves and stems to roots.

Other insects such as scales, leafhoppers, aphids, and true bugs usually attack the leaves of Alocasia causing stripling or spotting of foliage and leaf curling.

How to Treat

It is advised that you check your Alocasia plant (especially if you notice yellow spots) to see if there is a presence of the pests. 

If you detect their presence, go a step further to identify the type of pest that has attacked the plant. Identifying the pest that has attacked the plant will help you use the right elimination technique.

For instance, if your spot mealybugs on the Alocasia plant, treat by removing the pest with an alcohol-soaked cotton bud. 

Most pests like spider mites thrive in moist conditions. Therefore, ensure that you keep moisture level around the plant low to discourage pests such as spider mites from attacking the plant.

You can also get rid of pests by spreading the right insecticide. Please don’t spread any insecticide that you come across. 

Instead, research to see if the insecticide is effective in killing the pest without harming the plant.

6. Root rot

Root rot is a type of fungal infection that affects the root of the Alocasia plant. Of course, you may wonder how rot is associated with brown spots on the leaves. 

The general health of the root affects all other parts of the plant, including the leaves. If the root is not in good shape, a brown spot will start forming on the leaves.

Therefore, if you notice yellowing or wilting of the plant, then that is a clear sign that your alocasia has root rot. This fungal disease can spread very fast if left untreated for long.

How to Treat

Inspect all Alocasia plant roots in your garden and discard any plant that is affected by root rot. This is the first action to take to prevent the disease from spreading to other plants.

Another way of treating this disease is by keeping the PH of the soil below 5.5. Acidic soil is more resistant to thielaviopsis basicola, the fungus that causes root rot. 

Also, make sure that the pot has good drainage to prevent creating perfect conditions for fungi that cause root rot to thrive.

7. Fertilizer issues

Brown spots on the Alocasia are also caused by applying too much fertilizer or using the wrong fertilizer. 

For instance, if you apply too much fertilizer or apply it at the wrong time, there is a chance that your Alocasia plant may suffer from fertilizer burn (scorching of leaves as a result of excess fertilizer).

Too much fertilizer may also burn the plant’s roots, making it vulnerable to diseases and insects. 

Therefore, if you spot brown leaf on your Alocasia plant, then it could be as a result of too much fertilizer or using the wrong fertilizer.

How to Treat

The first solution to this problem is ensuring that you apply the right amount of fertilizer. Using the wrong fertilizer will attract pests that will cause more damage to the plant.

If the brown spot is a result of applying too much fertilizer, flush the soil to flush out excess fertilizer salt.

If this technique fails to work, then you will have no choice but to transfer your Alocasia plant to fresh soil that is free of fertilizer.

8. Watering Problem

If you notice brown spots of drying leaves, then that is a sign that your Alocasia plant does not receive enough water. 

Like other tropical plants, the Alocasia plant needs frequent watering to survive and thrive. 

If you don’t give it adequate water, brown spots will appear, and with time the entire leaf will wither and die.

The best way to know if your Alocasia plant does not receive enough water is by checking the condition of the soil. If the soil is too dry, then it means that the soil does not receive enough water.

How to Treat

The solution to under watering is providing enough water to your Alocasia plant. Ensure that you water the plant at least once every day (in the morning). 

Please don’t provide more water than what the plant requires. Overwatering is as bad as under-watering.

Also, research to understand the plant water needs and be consistent in providing adequate water.

9. Temperature Stress

Temperature stress in plants is divided into three categories depending on the stressor. They include high, chilling, or freezing.

Temperature stress has many negative effects on Alocasia, including reduced photosynthesis, low germination rates, brown spots, growth retardation, and death of the plant.

How to Treat

One of the ways to cut temperature stress in your Alocasia plant during the summer season is by providing good soaking water to the plant at least once per week. 

Also, ensure that the soil has the right moisture. During the winter season when the temperature is cool, protect the plant from extreme temperatures by keeping it in a safe location where the temperature is friendly to the plant.

FAQ 

How do I get rid of black spots on my Alocasia?

Black spots can spread to the whole leaf and can cause serious damage. So, it is important to stop them before they spread to the entire leaf. 

One of the best ways to get rid of black spots on your Alocasia is to cut all infected parts to prevent further spread. 

But, if the disease is in its early stage, you can use a suitable bactericide to get rid of black spots.

Can you revive a brown Alocasia?

Yes, there is a possibility of reviving a brown Alocasia, if the plant still has a few green leaves and a pliable stem. The root must also be alive. 

If your plant is suffering from too much water, stop adding plant food and fertilizer until the plant recovers fully. 

Also, keep the plant out of direct sunlight until their roof fully recovers. You will know your Alocasia plant has fully recovered when the plant leaves turn green and the soil is not too hard or too moist.

What does an overwatered Alocasia look like?

An overwatered Alocasia leaves often turn yellow and wilted. You will find wet-brown spots on leaves.

Overwater encourages fungal diseases like root rot. If you check the root system there will be a rotten or foul smell coming out from the potting soil.

Arifur Rahman

I'm the owner of gardenforindoor.com. After completing my bachelor of science in agriculture, I'm serving as a civil service officer at the Department of Agricultural Extension, Bangladesh. I started Garden For Indoor to make your indoor gardening journey easy and enjoyable.

Recent Posts