Common Bonsai Pests and Diseases: How to Spot and Treat Them

Bonsai pests and diseases are not uncommon and can be a reason for panic for many inexperienced bonsai enthusiasts. Most of them are, however, treatable if you know what to look for. 

Read on to find out what are the common pests you might encounter and how to keep your tree safe from pests and diseases. 

Common Bonsai Pests to Look Out For

There are many critters that live in the soil of your tree and hide in the leaves or the bark. Some of them are easy to spot but others can be tricky to identify. Here are some of the common bonsai pests and how to spot them: 

Spider Mites 

Spider mites are one of the most common bonsai pests that you will encounter. These tiny spiders normally live on the underside of the leaves. They are usually found on older leaves and often spin a silky web at the button of the leaf where they lay eggs. 

Aphids

Aphids are another one of the common bugs that can infest your tree. They are usually easy to recognise due to their pear-shaped body and are easy to spot as they love to crowd together, usually on the underside of the leaves. These tiny pests suck the sap from your bonsai, leaving behind a sugary secrete that can attract ants and cause your bonsai to mould.  

Mealybugs

Mealybugs are small, oval-shaped insects that thrive in cool and dark places, and could be hiding in your bonsai tree right now. These common bonsai pests normally hide in the soil around the roots of the tree or in the small spaces between a leaf and the branch. 

Scales

These tiny oval-shaped insects live in the bark of your tree and feed on it. At an initial glance they may appear like brown bumps on the trunk of the tree so you have to look very closely to notice them. You can also find them clumped up on the underside of the leaves where the leaf and the bark meet. 

Slugs or Snails

These pesky creatures often like to nibble on the leaves of your bonsai and can spread mould, fungus and diseases to your tree. They thrive in damp weather and most often attack outdoor bonsai trees, leaving behind slimy trails all over the branches and leaves of your tree. 

How to Treat Bonsai Pests? 

As soon as you notice a pest infestation on your tree you should isolate it from any other trees before the pests can spread across your whole bonsai collection. Gently spray the leaves with lukewarm soapy water to wash away most of the insects and then treat the tree with bug spray if required. 

Signs of Infections and Fungicides on Your Bonsai Tree 

Although there are many reasons why you might be noticing spots on the leaves of your bonsai, usually it’s a surefire sign of one of the common bonsai diseases – fungal infection. Here are the different types of spots to look out for when inspecting your tree for potential disease:  

White Spots on Bonsai Leaves

White spots, powdery film or mildew on the leaves of your tree is a sign of a fungal infection, most commonly found on broadleaf tree species such as the Chinese Elm. While it’s not something to be too concerned about, you should treat it quickly as it can lead to your tree losing its leaves which in turn can impact the overall health of your tree. 

Black Spots on Bonsai Leaves

Black spots on the leaves of your bonsai in most cases indicate that your tree is suffering from a fungal infection. If left untreated, what starts out as tiny black spots can soon grow into patches and potentially take over the whole leaf. 

Brown Spots on Bonsai Leaves

Brown or orange spots usually on the underside of the leaves can often be a sign of rust – another common fungus that can negatively affect the health of your tree. This fungus looks similarly to rusted metal, which is where it gets its name from. If left untreated it can spread over to the branches of your bonsai covering them in a rusty-looking powder.  

Another reason for brown spots on your bonsai’s leaves can be sunburn during the summer months. To avoid this, keep your bonsai safe and away from direct sunlight. 

How to Treat Fungal Infections? 

The first thing to do when you notice signs of fungus on your bonsai is to move the affected tree away from any other trees or plants to prevent the risk of cross-contamination 

The best way to get rid of any type of fungal infections is by pruning away the infected leaves and treating your tree with a fungicide. If you’re unsure which one is best, always consult a specialist before buying. 

You might have to reapply the fungicide several times and keep an eye on your tree to make sure the infection doesn’t come back. 

How to Keep Your Bonsai Healthy 

So how do you keep diseases and pests away from your bonsai? The key is making sure that your tree is overall healthy. Here are some of the best ways to keep your bonsai pest-free:

• Watering – Knowing how to properly water your bonsai can help keep it safe from diseases and prevent pest infestations. While you should make sure that your tree is a bit damp to the touch, the water should be able to drain all the way through and not sit in the soil.  
• Light – It’s important to know how much light your bonsai tree needs as different tree species have different requirements. If your tree isn’t getting enough light, it can promote the growth of mould and mildew.
• Soil – Make sure you pick up any fallen leaves or flowers as they can rot and create the perfect environment for pests. Using a well-draining bonsai soil is also important as it will allow air and water circulation. 
• Nutrients – A healthy and well-nourished bonsai is less susceptible to fungal infections and pests. During the growing season give your tree suitable bonsai food to ensure it has all the needed nutrients.   

Browse our beautiful bonsai trees and accessories today and read our Care Hub for more useful information about bonsai tree care!