Category Archives: Bonsai Pests and Disease

Bonsai Pests and Diseases

Part 8 of a series by Eugene Howell

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Japanese ZelkovaIn part 7 of this series (linked to at the bottom of this page) we started talking about bonsai pests and diseases. Today we’ll continue the topic of fungus that can adversely affect your bonsai trees.

Although there are many variations in symptoms, if you see black or brown spots begin to develop on a leaf, and if these spots begin to grow in size, you very likely have a fungus problem. With some fungi, these spots will develop along the edges of the leaves and thus look very similar to water stress (this is one of those hard-to-diagnose symptoms). In most cases, however, the spots will appear across the entire leaf surface. If the spots penetrate completely through the leaf, from the top side to the bottom side, your plant definitely has a fungus. Keep in mind, however, that not all fungi produce these symptoms.
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Bonsai Diseases

Part 7 of a series by Eugene Howell

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Japanese White Pine Zui-sho pinus parviflora}Many bonsai enthusiasts and gardeners in general, have a tough time diagnosing plant disease and then have trouble deciding how to treat it. The reason may be because there are so many diseases, some of which have unusual or often very subtle symptoms, many of which are similar. So the average bonsai artist looks at a diseased leaf and doesn’t know what the problem may be or how to treat it.

There are three broad categories of bonsai diseases. They are fungus, virus and bacteria. Unfortunately there are no cures for viral and bacterial diseases in plants. But it’s critical that you know and recognize them because it’s very easy to inadvertently spread the disease from bonsai to bonsai as you work on your trees. Learning to recognize plant disease when it occurs will allow you to quarantine the tree away from your other bonsai. Remember to wash your hands thoroughly after handling the diseased tree before working on any other bonsai.
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Bonsai Tree Bugs

Part 6 of a series by Eugene Howell

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Bonsai ConventionWe’re continuing our discussion about the pests that can infest your bonsai trees. My previous post talked about aphids and is linked to at the bottom of this page. In it we learned how to recognize when your bonsai have them, and what to do about it.

In this post we will discuss how to identify mealy bugs, scale, spider mites and thrip, and how to get rid of them.

Mealy bugs are easy to identify but more difficult to eliminate than aphids. Like aphids, mealy bugs mainly stay on the undersides of leaves, along the stems, and on the branches and trunk. They can be identified by their protective coating which is usually white and looks like a tiny bit of cotton.
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Bonsai Pests

Part 5 of a series by Eugene Howell

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Pinus BonsaiYou’ve got a beautiful bonsai that’s planted in the perfect bonsai soil, watered daily, fertilized well during the proper part of the year, pinched when needed, and repotted every few years. You’re rewarded with a tree that grows vigorously, blooms profusely and is the picture of perfect health. Then one day you notice the leaves beginning to do strange things. Some have a mottled appearance, with tiny yellow spots all over them and others are beginning to curl up like a rolled cigar. If this hasn’t happened to you before, it can leave you puzzled as to what’s going on.
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