How Do You Treat Bougainvillea Leaf Spots?

When it comes to diseases, you want to steer clear of Bougainvillea leaf spots on your bonsai. They can spread to other parts of your tree, so it’s best that you treat them as soon as possible.

In this guide, we’ll show you what causes them, how you can identify them, and what steps you can take to correct the problem.

Bougainvillea Leaf Spots

How to Treat Bougainvillea Leaf Spots

The leaf spot disease is one that loves to develop on shade and ornamental trees. It’s mostly the result of fungi, but there are some bacteria that cause it too.

Before we go into detail about the symptoms, causes, and which sprays you can use, here’s a risk management approach for treating leaf spots on your Bougainvillea bonsai.

1.   Just Live with it

In most cases, your Bougainvillea will be fine with a few leaf spots. You may see new leaves appear with no signs of the disease, in which case it’s worked it out its system. However, if you see it spreading throughout the rest of your bonsai tree, it’s time to take further action.

2.   Remove Infected Areas

You can remove any foliage that has signs of leaf spot, as long as you don’t cut all the leaves. It will prevent fungal spores from spreading to the rest of the bonsai. If you catch it early enough, you shouldn’t see any further indications of the disease. If it continues, you can move to the next step.

3.   Let the Leaves Dry Out

Overhead watering or misting can also spread leaf spots on your Bougainvillea. Give your leaves a chance to dry until the disease vanishes. We also recommend you prune any dense foliage to allow air circulation and prevent further spread to other leaves. If you need to spray, do so in the morning so the sun has a chance to dry it during the day.

4.   Care for Your Bonsai

After you defoliate your Bougainvillea, ensure that you provide proper care until it’s at full health again. Feed it nitrogen fertilizer to promote leaf growth, but don’t overwater, as it may invite more pests to feast on your bonsai. Make sure there’s enough sunlight for the new leaves to create energy and exchange gases.

5.   Spray Fungicide

When you see the leaf spots are getting worse on your Bougainvillea, you can treat it with fungicide. It won’t remove the condition, but it will prevent it from spreading any spore further to the rest of the bonsai. Check the instructions on the label to see how often you need to apply it.

6.   Replace Your Tree as a Last Resort

When nothing else works and it seems like your bonsai is at its last, you can replace it with a new Bougainvillea. It prevents the spores from spreading to your other bonsai trees while you won’t need to fight the disease. There are some nursing centers that will take them from you in an attempt to rescue them.

Bougainvillea Leaf Spots

Symptoms of Bougainvillea Leaf Spots

For you to treat Bougainvillea leaf spots, you need to be able to identify them properly. While the name does seem self-explanatory, you may be dealing with other pests or diseases.

The leaf spots are generally brown or black, but they can also be a tan color. You’ll either see concentric rings or small margins, while the size can vary from small to large depending on the stage of infection. They may even form clusters.

If you let it develop further, the fungal spots may combine and create massive blotches. If these markings become angular, we refer to them as ‘anthracnose’. In this situation, the leaves may eventually become yellow or fall off.

What Causes Leaf Spots on Bougainvillea?

As you already know by now, leaf spot is a fungal disease. It’s caused by fungal spores that travel via the air and land on damp surfaces to reproduce. If you regularly mist or water your bonsai leaves, it creates the optimal conditions for them to thrive, especially when it’s warm and there’s insufficient light.

Once it has made a home on your Bougainvillea bonsai, it starts the sporulation process, which is how fungi reproduce. It causes the leaf spot to appear on your leaf as they develop new life. As the spores grow and spread, more spots appear in larger sizes. When two or more rings join, they create blotches.

The Life Cycle of Leaf spots

While we’ve given you a general overview of how leaf spots form on Bougainvilleas, it’s better to get an overview of the life cycle. You can then assess at which stage the disease has reached on your bonsai so you can deal with it more effectively:

  1. The fungal spores leave their current nest and travel by air or water until they find a new home
  2. A spore lands on the leaf surface where it feels warm, wet, and dark
  3. It starts the sporulation process and reproduces, creating more spores
  4. The process repeats, spreading to new leaves and surfaces
  5. When there are no more leaves to contaminate, new spores move to a new location or die when none are found or fungicide is applied

Bougainvillea Leaf Spots

What Do You Spray For Leaf Spots?

There are plenty of fungicides on the market you can try, but we recommend buying one that states it’s organic. These are safer and won’t harm the rest of your bonsai tree.

Most of the products contain copper octanate or sulfur, but you can also make a mixture of bicarbonate of soda. Just add half a teaspoon with every gallon of water. Usually, you’ll apply it once a week until the problem goes away or the spreading stops, but some products may indicate more regular spraying.

Whatever you do, ensure that the leaves dry during the day and don’t allow the moisture to rest overnight. The moisture may cause more damage or attract pests to your tree.

How Do You Treat Leaf Spots Naturally?

To treat the leaf spots on your Bougainvillea naturally, you can leave the condition as it is and hope it goes away. A better option is to remove the infected leaves so that the spores don’t spread. Also, don’t water the leaves, as this may help the fungi travel to other areas of your bonsai.

If you want to encourage good fungus to fight the bad one, you can layer cornmeal on the soil with mulch over it. It helps if you use bark. Some people also suggest spreading cinnamon over the infected areas, but it might not work with all Bougainvillea species.

Bougainvillea Leaf Spots

Will Leaf Spot Go Away On Its Own?

As the leaf spot disease has a specific life cycle, you could just wait for the spores to die out or move away from your bonsai tree. The conditions may end up not being as favorable as the fungi had hoped, so they may not last long. Of course, there are some things you can do to make their stay unpleasant, such as removing infected leaves.

If you practice proper bonsai care for your Bougainvillea, the spores won’t want to reproduce. Supply enough food and sunlight, and your tree may have the resistance to withstand the disease.

How Long Does It Take For Leaf Spot To Go Away?

How long the leaf spot will remain on your Bougainvillea bonsai depends on the conditions and steps you take to treat it. If you just leave it in dark, warm areas, it may take a long time to vanish. If you improve the situation or apply fungicide, it can take anywhere between two weeks to a month or longer.

The primary concern is ensuring that it doesn’t spread to any of your other ornamental or low light bonsais. Any light breeze can quickly carry spores to nearby trees, infecting their leaves. It may be necessary to isolate your Bougainvillea until the condition improves.

Bougainvillea Leaf Spots

Final Thoughts

While leaf spots don’t necessarily cause any permanent damage to your bonsai tree, it’s better that you treat them to prevent the situation from becoming worse. For the most part, removing the infected areas carefully should do the trick. If not, we hope our recommended techniques will help you.

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Shaun has two passions in life that combine into an extravagant show on Bonsai Alchemist. The one is for writing and the second bonsais. He’s been writing fantasy and horror novels since 2000, while also creating online content since 2015. He’s involved with writing for films and games. Finally, he’s also the owner of a book publishing company.

He received his first bonsai as a gift in 2009 and has been growing several species in his quiet home in South Africa. He prefers propagating new life instead of buying bonsais at the store. His son and daughter share his love for nature, while his wife stares on at her introverted hermit husband.


Shaun M Jooste


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