Bonsai: Detect and combat diseases and pests

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Bonsai trees are naturally very robust. And yet, wrong care can lead to various diseases. Here is a brief overview of the most common diseases and pests and how to fight them.

Bonsai Combat diseases and pests: Keeps your trees healthy

His bonsai pupils are always in the eye. They just need special care so they can develop beautifully. But the regular review also has its positives. Disease symptoms get along quickly and can intervene accordingly.

The most common care mistakes occur in the water supply. With the sheet diagnosis small errors can be recognized immediately:

Your bonsai suddenly gets yellow, withered or dry leaves that eventually fall off - then it clearly gets too little water. On the other hand, if the leaves gradually turn yellow and die, too much water, too much fertilizer or even a lack of nutrients are responsible.

Β»Reading tip: Bonsai fertilize - So the plant gets all the important nutrients

Virus and fungal diseases in bonsai trees

Bonsai can catch a virus or get a fungus. They recognize the diseases on pale, yellowish leaves or needles. The branches die off. Quarantine and hygiene are the initial measures. Often the triggers are transmitted by touch, so a separate as possible, clean handling is extremely important.

Remove the infected parts and separate the affected plant. Fungi can usually be combated well with a fungicide (My recommendation: Bestseller No. 1 Compo Duaxo Universal Mushroom-Free), as long as the disease has not yet covered the whole bonsai.

➜ Stem rot and root rot


Root rot and stalk rot are caused by bacteria or fungi. The stalk rot destroys the bonsai from the inside. The trunk and the branches turn reddish-brown from the inside. The disease mainly affects yew, walnut, horse chestnut, pine, book and olive. Waterlogging and a bad exchange of air favor stalk rot.

The root rot occurs at the root ball and destroys the bonsai from below. Brown, withered leaves and a foul odor are usually the first signs. The roots become soft and muddy, the water transport does not work anymore. Waterlogging is also a factor that affects root rot. So always think of a good drainage and regulate the water balance of the bonsai carefully!


It is often advised to completely dispose of bonsai trees affected by stalk or root rot. You can also remove affected parts generously. Then place the bonsai in fresh substrate and make sure to keep it separate until you can be sure that it has recovered well. Fungicides (see above) act against fungi that cause root and stem rot.

If nothing works, remember not only to remove the bonsai, but also to thoroughly clean the planter, preferably with alcohol.

➜ Fire hazard: fire blight on bonsai

The fire blight is triggered by bacteria. The leaves turn brown to black, the tree dies. There is no antidote, the bonsai unfortunately has to be destroyed.

Pests on bonsai trees

➜ aphids:

On the bonsai, aphids often spread. Bathe the bonsai headfirst in a mixture of dishwashing liquid and water, preferably repeat several times.

➜ Scale insects:

Scale insects also harm the bonsai. Access a bio-based paraffin oil-based spray, e.g. the Austrittspritzmittel of Bayer.

➜ blood louse:

The blood louse is the most dangerous type of louse. It sucks on the woody parts and causes malignant ulcers. Again, you can use the just mentioned biological spray.

➜ Apple tree spider moth:

The apple tree moth is another well-known bonsai pest. It is a moth that drops its eggs on the shoots. The hatched caterpillars eat the bonsai in a very short time completely bald. Visually, the infestation is shown by a gray-white web between the leaves. You can try to scrape off the eggs and collect the caterpillars. Again, place the bonsai separately so that the pests do not spread to other plants.

Video Board: How To Deal With Black Spot Leaf Disease.

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