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8 Causes Brown Spots on Avocado Leaves (And Solutions)

Growing your Avocado plant indoors is not as complicated as growing it outside. With proper care and patience, your plant will thrive and add scenic beauty to your house.

Though it’s easy to take care of, there are still times that your plant needs extra attention, especially when dealing with unnecessary situations. One of those uncertainties is having brown spots on your Avocado leaves.

The best process that you can do in dealing with those brown spots in your Avocado is to start regulating the water intake, provide shading to avoid excessive sunlight, supply the necessary nutrient requirement, and follow the proper procedures in eliminating pathogens.

There are many factors causing brown spots on avocado leaves. To give you an idea of what those causes are and how to deal with them, let’s continue reading this article.

Indoor potted avocado leaves showing brown spots
Brown Spots on Avocado Leaves

How to Identify Brown Spots on Avocado Leaves?

Before jumping to the causes, you need to know first how to identify brown spots in your Avocado plant. 

Those brown spots are usually caused by either fungal or pest infestation.

The first observation that you will find is small dot-like brown spots under your plant’s leaves. Those spots will soon emerge on the top of the leaf until it becomes chlorotic, which eventually withers.

There are also cases that, when some of your Avocado leaves start to wither, the bark and stems will become exposed to sunlight, causing them sunburn damage.

What Causes Brown Spots on Avocado Leaves?

Though we can easily say that those brown spots in your Avocado leaves are caused by infestations, we still need to consider checking other factors that might be affecting your plant.

Avocado Algal Leaf Spot

This infection is caused by parasitic algae known as Cephaleuros Virescens, the only parasitic algae that can cause plant disease.

This parasite reduces your plant’s capability to perform photosynthesis, thus resulting in brown-rust colored spots that usually start on the leaves and sooner moves into the stems and twigs of your Avocado.

You will also see some yellowish or green-colored spots appearing from underneath your plant’s leaves in addition to the symptoms. 

It might look devastating, but if appropriately treated, this disease will not create any further damage to your plant aside from that visible deterioration in its appearance. (Source: University of Hawaiʻi at Mānoa)

Treatments:

  1. Algal leaf spot disease highly depends on moisty parts of your Avocado to survive, so placing your plant in a high-temperature area, preferably near the window, will limit the lifespan of the infesting algae.
  1. Check on your plant’s drainage to ensure that there’s no excess water in your pot dish.
  1. Pruning your plant is an excellent process in eliminating damaged leaves to give way to a new batch of leaves to sprout. Pruning will also open a passage for air to circulate, which will help your plant’s bark and stems to dry quickly.
  1. You can prevent new brown spots from destroying the beauty of your Avocado by spraying copper fungicide once every week.

Fungal Diseases

The common reason why there is a fungal infestation on your Avocado is because of undrained pots and a humid environment that causes excessive moisture in your plant.

With that kind of moisty situation, fungi will most likely grow and soon invade your Avocado plant.

There are many possible fungi that you can incorporate with the brown spots of your Avocado leaves.

To know what kind of fungi your plant might be dealing with, let’s take a look at the chart below.

DiseaseReasonsSymptoms

Anthracnose
This disease directly attacks the leaves of your Avocado, causing severe damage to your plant’s system.

It usually occurs during winter and wet seasons.
The common visible symptoms apart from brown spots are severe leaf drop and scorched appearance of some leaves.


Septoria Leaf Spot
This leaf spot is obviously caused by Septoria, a fungus that commonly resides on crops and vegetables.

This usually appears on your plant’s lower leaves, where a wet and humid environment is present.
Numerous visible brown spots underneath your plant’s leaves and yellowing or withering leaves are some of the main symptoms of this particular disease.


Alternaria leaf blight
Caused by Alternaria, a common plant pathogen that infests on your Avocado leaves, this disease usually infects the mature leaves of your plant.

They love to germinate during wet, rainy seasons, but they are most dangerous in warm, moist environments. 
The symptoms will start from the mature leaves of your plant.

It will first show small brown spots with a yellowish margin.

If not prevented, the whole leaves will turn brown and eventually wither.




Downy Mildew



This disease is common in cool, humid temperatures, usually during early spring.

The pathogen travels through the air in the form of spores.  
The symptoms commonly appear after rain.

You will notice yellow and white patches on the upper part of your plant’s leaves, while underneath, you will see a grayish cotton-like substance.

Over time, the spots on your leaves will turn brown and soon will drop.


Powdery Mildew
This fungal disease is a common issue in a garden.

It reduces the quality of your plant’s leaves and hinders the process of photosynthesis.

Different from other conditions, Powdery Mildew thrives in a hot, dry environment.
The symptoms are pronounced, you will see flour-like dust on the top part of your leaves.

This may also lead to leaf foliage and disfiguration.

Treatments:

Anthracnose
  1. If your plant is suffering any fungal attacks, it’s best to isolate it from other plants to avoid the spread of the infestation.
  1. Remove infected areas and immediately dispose of them into your garbage bin.
  1. Check the drainage system and remove excess water.
  1. Give your plant an adequate amount of sunlight to aid the drying process.
  1. Apply fungicide directly on the leaves where the infestation happens.
Septoria Leaf Spot
  1. Remove all the infected parts of your Avocado plant and dispose of them immediately. Don’t use those infected areas as compost.
  1. Wash your hands before engaging in other plants.
  1. Sterilize all your tools to avoid transferring spores to your healthy plants.
  1. Use Copper-based fungicide to control and eliminate the fungi. You can also use biological fungicides like bacillus subtilis to effectively terminate the culprits.
  1. Lastly, clean your surroundings. As much as possible, make sure that there are no signs of fungal infestation present to avoid recurrence of this situation.
Alternaria Leaf Blight
  1. If you suspect that your Avocado is suffering from Alternaria Leaf Blight, you may apply copper-based fungicides once a week.
  1. Immediately stop or limit watering your Avocado plant. As much as possible, do not sprinkle/spray water overhead your plant to avoid the building of moisture on the leaves.
  1. Prune your plant to allow air circulation and reduce fungal infection to other leaves.
  1. Add some layer of organic compost to prevent spores from coming back to your Avocado plant.
  1. Maintain cleanliness by sanitizing all your tools and disposing of all infected parts of your Avocado.
Downy Mildew
  1. Remove all plant debris, make sure that you dispose of it away from your plant’s area. 
  1. Allow 3 to 5 inches spacing between your plants to prevent transferring of fungal spores.
  1. If your apartment has a humid environment, consider relocating your plant in a medium to the high-temperature area.
  1. When watering your Avocado, avoid overhead irrigation to keep the leaves dry and free from moisture.
  1. Apply copper-based fungicides once a week. Check the price of mancozeb on Amazon. Do not use fungicide during the rainy season to give enough time for the treatment to dry.
Powdery Mildew
  1. In case any symptoms appear, consider relocating your plant to a less humid area and allow proper air circulation.
  1. Use a mixture of bicarbonate solution. Just mix 1 teaspoon of baking soda in a liter of water. Thoroughly spray it on the affected leaves.
  1. Don’t overwater your plant. To know if your plant needs water, simply touch if the soil is dry.
  1. Remove excess water in the drainage of your plant. If possible, drain the pot first before placing it back into the dish.

Bacterial Diseases

Another vital cause that you need to watch out for is the effect of bacterial infestations in your Avocado plant.

Typically Avocado is only prone to fungal attacks and not on bacterial invasions.

But during warm, humid seasons, your plant might experience Bacterial Soft Rot.

This bacterial disease is known for its capability of causing the plant’s structure to fall apart by directly attacking its pectate molecules.

Naturally, these bacterias were spread by insects from one plant to another. It will then enter your plant through open wounds, usually caused by tools or other natural openings. (Source: University of Wisconsin – Madison)

The common symptoms that you will see are the sudden discoloration of your plant’s leaves accompanied by the appearance of water-soaked spots and yellowish-brown spots. You will also notice a strong foul odor coming from the leaves of your plant.

Treatments:

As of now, there’s no identified cure to save your Avocado plant when its tissue has already been affected by this bacterial disease.

The best thing that you can do to somehow keep your plant is to propagate it.

Propagating Your Avocado Plant

  1. Look for healthy uninfected leaves from your plant, preferably choose new shoots with leaves that are not yet fully opened.
  1. Cut 2 to 3 stalks around 5 inches from the tip of the stem.
  1. Make two small cuts on both sides of the stem. In that way, you are increasing the chance of rooting the cuttings.
  1. Place the cutting into a cup of indole butyric acid to stimulate your plant’s roots’ growth. In place, make sure that the cut area is dipped properly.
  1. In a small pot, prepare your soil. Ideally, the best pot mixture is a combination of peat moss and perlite.
  1. Plant your cuttings and water them adequately.
  1. Locate your plant in a sunny area but avoid spots with too much direct hit of sunlight.
  1. Water your cuttings every 7 to 10 days of interval or whenever the soil gets dry.
  1. Apply fertilizer once every 3 weeks for a year, after that, only apply four times a year.
  1. If your plant has overgrown the pot, consider repotting it to a bigger pot.

Edema

Edema is a physiological deterioration that usually develops when there’s an abundant presence of warm soil water and a humid environment.

Within that kind of situation, the roots tend to absorb water faster than the leaves can transpire, which results in the accumulation of excess water in your plant’s leaves.

This water build-up will force the epidermal cells of your plant to stretch and soon collapse. 

If your plant is suffering from edema, you will see that its leaves have small brown spots, also known as edema spots, and corky veins together with a crusty texture.

Treatments:

  1. The first thing you need to consider adjusting is your watering system, especially during the winter season. Remove the pot dish of your plant or add holes underneath for proper draining. 
  1. If possible, relocate your plant in a high-temperature room with less humidity.
  1. Avoid fertilizing your plant during cold weather. Always check the soil using a soil test kit to properly assess the nutrient requirement of your plant.
  1. In case symptoms still persist, repot your plant using well-drained potting soil.

Excess Light/Scorching

Your lighting system is a critical factor in growing the Avocado plant indoors.

Your plant needs an adequate amount of light to successfully thrive. Otherwise, its growth process will deteriorate. 

Though your Avocado enjoys the heat of sunlight, that doesn’t mean that it’s immune to scorching.

It usually happens to young Avocado or when you suddenly expose your plant to bright sunlight from a normal light inside your house.

Scorching can cause a brown blemish in your Avocado leaves, and if not treated, it will wilt and eventually drop. Avocado leaves curling is a common issue because of excess sun exposure.

Treatments:

  1. The best solution is to relocate your plant in a high-temperature area with a less direct hit of sunlight. Preferably in window sills located in the east part of your house.
  1. If relocation is impossible, consider installing blinds to control the entry of light.
  1. Give adequate water supply to sustain its physiological needs.

Frost Damage

Avocado is considered one of the many frost-sensitive plants in the world. Even if it comes from the origin of subtropical trees, avocados can only endure low-temperature levels for a minimum interval of time.

The cold weather forces the sap of your plant to freeze, thus resulting in cell damage. On severe occasions, it might also damage the branches and stems of your plant.    

Treatments:

  1. Remove your plant away from the window to lessen the burden of exposing too much cold weather.
  1. Monitor the soil temperature regularly to prevent excessive moisture. 
  1. Stop watering your plant, otherwise, it will experience soggy conditions that can lead to crucial damage to your plant’s root system. 
  1. Generally, all you need to do is observe, maximize what you can do, and wait for your plant to recover.

Insect Infestation

Insects may also be a culprit regarding the brown spots in your Avocado. That’s why it’s highly advisable to thoroughly check the plant before buying to avoid bringing this pest home.

There are some insects that we can immediately accuse, but to further assess if there are really pest infestations happening in your plant, here are the details of each of them:

Persea Mite

Identification: A microscopic yellowish mite that is actually of the same size of a period. They germinate mostly in dry summer seasons.

Causes: Commonly, it attacks the bottom part of the leaves, which causes necrotic spots. These spots will block the supply of carbohydrates from the leaves resulting in leaf dropping and withering.

Symptoms: You will see some brown necrotic spots in the leaves of your plant. You will also notice webbings in every spot that usually shines when exposed to sunlight.

Treatment:

  1. Plant isolation is recommended to avoid mite reproduction.
  1. Apply an insecticidal oil diluted in water. Make sure to spray the upper portion and underneath your plant’s leaves.
  1. You can also use high-pressure spray or hose to eliminate the culprit. Though, this process is not advisable for young Avocado plants.

Avocado Thrips

Identification: These are yellow insects with a typical 1mm size. Though they can fly, still their best way to transport is through wind propagation.

Causes: Like normal thrips, they attack the tips and edges of your Avocado leaves. They also discharge honeydew that invites the presence of fungi.

Symptoms: Aside from typical brown spots, you will also encounter some dark leathery patches on the upper side surface or your plant’s leaves. These insects even leave some small black pellets.

Treatment:

  1. Organically, these pests can be controlled by their natural predators such as bugs and beetles.
  1. Eliminate the presence of ants to allow predators of thrips to visit your plant.

Mealybugs

Identification: These are unarmored, oval-shaped insects that usually appear as a cotton-like substance on the upper part of your plant’s leaves.

Causes: Naturally, mealybugs suck your plant’s juices, which causes the leaves to stunt. These insects also excrete honeydew that deteriorates the quality of your Avocado.

Treatment:

  1. Rub the leaves with cotton soaked in alcohol. If possible, handpick those visible mealybugs. 
  1. For severe cases, use a high-pressure hose or spray neem oil directly to your plant’s leaves. Again, high-pressure equipment is not advisable to use for young Avocado plants.
  1. If the infestation continues, dispose of your plant to avoid the mealybug transfer.

Ants

Identification: These are regular house ants.

Causes: Ants do not feed on any part of your Avocado, and neither does it bring any harmful damage to your plant. The only lethal contribution that they do is driving away from the natural predators of your plant’s pests.

Symptoms: These ants visible appearance is a sufficient symptom to consider.

Treatments:

  1. Dealing with ants is technically blocking off all their possible entrance towards your plant’s leaves.
  1. Surround the base of your plant with any sticky materials to entrap the invaders.
  1. Cut off leaves or stems that ants can use as an entry point towards your plant.

Fertilizer Burn

Although fertilizer is essential to your plant’s growth, overusing it may cause you to burn leaves and other parts of your Avocado. 

To prevent that scenario, let’s analyze the nutrients affecting the growth of your Avocado.

Iron

Problems: Iron deficiency occurs in soil with high pH. A humid environment and excessive moisture could worsen this deficiency.

Symptoms: The common symptoms are leaf discoloration and brown spotting, defoliation, and marginal leaf burn.

Corrections: Increase the presence of iron in your soil by using peat moss and other organic compost.

Nitrogen

Problems: Nitrogen deficiency is caused by its natural solubility in water. The more presence of water, the lesser amount of nitrogen will travel to the leaves.

Symptoms: Yellowing of leaves and the sudden appearance of dark brown spots

Corrections: Water moderately and add ammonium nitrate to the soil.

Zinc

Problems: Zinc is not as abundant as any other nutrients. Therefore, deficiency with this element is expected.

Symptoms: Discoloration within the leaf margins, deterioration of the leaf’s structure, and noticeable dark spots are some of the symptoms you will detect.

Corrections: Apply kelp extract or any other foliar spray to boost the presence of zinc.

Sodium Chloride

Problems: Commonly, the problem with sodium chloride, also known as salt, is its imprudent appearance.

Symptoms: Too much salt can burn the mature leaves of your Avocado. You will also notice some discoloration and premature defoliation.

Corrections: Stop fertilizing your plant until the symptoms stop. Apply gypsum or lime to negate the presence of salt.

How to Prevent Brown Spots on Avocado Leaves?

As frustrating as it is, dealing with the brown spots in your Avocado takes a lot of hard work, understanding, and patience so you can successfully save your plant from that disaster.

The best way not to undergo that situation is by doing practical measures that could prevent the causes of brown spots from coming into your house.

  1. As a general rule, always check the plant thoroughly before purchasing and bringing it home.
  1. Provide adequate and moderate sunlight to your Avocado.
  1. Avoid placing your plant in a humid environment.
  1. Proper watering is necessary for your plant’s growth. Avoid overhead watering to prevent fungal and bacterial infestation.
  1. Maintain a proper drainage system in your pot to prevent waterlogging.
  1. Don’t over-fertilize your Avocado. As much as possible, use a proper soil testing kit to identify the needed nutrients. 
  1. Apply proper propagation if the situation comes to the worst.
  1. Lastly, bear in mind that the key to prevention is cleanliness. Sanitize your tools every after use, thoroughly wash your hands, and dispose of your plant garbage properly.

Final Words

Avocado is a perfect addition to your home. With its oval leaves and shiny texture, it will surely complement the interior of your house.

Though this plant is known to have brown spots occasionally, dealing with it is relatively feasible if you have the right understanding and proper treatment.

If you’re Avocado is having these brown spots, check the symptoms first before applying any solutions.

Always remember that your Avocado plant requires attention and lots of patience to thrive.