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Protecting Your Bonsai From Disease

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Depending upon what species your Bonsai tree is, there are several diseases to watch out for...
Bonsai plants are not immune from disease. Just as with the larger sized versions, A diseased Bonsai trees can experience severe damage from mildew, rust, and other specific fungi. In caring for your Bonsai, you might run into such problems as:
  • Chalky Mildew - Powdery splotches of white or gray, on the leaves and stems of plants.

  • Honey Fungus - This is a common fungus (yellowish-brown (honey) coloured mushrooms) that exists frequently on dead plant material, but has the ability to become parasitic on living roots of many kinds of plants.

  • Leaf Spots - Leaf Spots or leaf infections are caused by a variety of fungi and some bacteria on many trees.

  • Rust - Rust is caused by 4,000 different fungi. It is usually appears as yellow, orange, red, rust, brown, or black powdery pustules on leaves, young shoots, and fruits of sick Bonsai trees.

  • Verticilliosis - Caused by the fungi of the genus Verticillium, this disease is characterized by by drooping and shriveling of the affected plant - a wilting Bonsai; usually caused by the parasitic attack of the roots.

Treating Your Diseased Bonsai Tree

Mildew is a yeast noted for its whitish, chalky mycelium. Mildew's main section of fungus has a loose networking structure of fragile hyphae or filaments that shape the fungus and consists of feeding tubes, which replicates hyphae. Mildew will attack stems, buds, leaves, etc. Mildew will grow thick around the plant, which distorts the leaf blades. The leaves and blades will finally shrivel and finally the tree will wilt away.

To rid your plant of chalky mildew, you can treat the bonsai with synthetic or mineral fungicides. You will need to cut off any branches, which are infested. Destroy any cuttings, or infested branches immediately. Use your sprays. You can use sulphur in the spring to prevent mildew. Treating the problem straight away is the key to growing healthy bonsai.

Leaf Spots, as the name implies, affect the leaves of trees. The spots start out white and change to brown, or gray with black hollow rings. These then develop into lesions. Often these spots form as 3-sided polygon, or triangles. The foliage affected, will wither. And you may notice granules starting appear in the center of the leaves.

How to treat Leaf Spots:  As soon as you notice symptoms, such as the ones above, get rid of any leaves that show disease and destroy them. NOTE:  Do not place any plant material from diseased plants into your compost pile. any unaffected leaves can be sprayed with copper-based chemicals that kill fungi, such as fungicides. DO NOT water or mist the plants in direct sunbeams. Also, DO NOT add, too much moisture to the the soil.

Honey Fungus. Bonsai are subject to rotting roots. Being in enclosed containers with shortened and cut roots does leave many species of Bonsai trees open to root problems. Honey fungus attacks sickly trees, especially those that have been pierced by insects or damaged during cutting. If you notice the roots turning brown or notice rhizomorphs (black threads of fungus parts moving from host to host), you will need to treat your tree. You may also find the rhizomorphs or brown spots beneath the bark.

There are other signs of Honey fungus or other problems to be aware of. If new shoots don't seem to be growing, it is an indication that your plant needs help. If the roots are rotting, you will notice leaves and/or needles dropping off when they shouldn't be. Overall , a tree infested with Honey fungus will wither and the branches will decompose.

To treat and protect your bonsai, once you notice an indications of rotting, isolate this tree from other bonsai plants. You can try spraying your tree with fungicide and remove in infected plant material. Sadly, the disease honey fungus, or root rotting is deadly. More often than not, by the time you notice the signs of a honey fungus infection the diseased bonsai tree has reached a point beyond saving.

Verticilliosis is a general term referring to any plant disease, usually a soil borne fungus that causes your Bonsai to droop and wilt. Since there is not one specific fungus that causes Verticilliosis, this is a good time to briefly explain a little bit more about fungus.

Fungus growth on a Bonsai usually starts from spores finding a weak spot on the plant. Fungus replicate via spores. Ths fungus then forms either a single cell or a multi-cellular plant life which lacks chlorophyll. To survive and grow, the fungus absorbs nutrients from adjacent macrobiotic matters, usually, dying and/or decaying plant and animal materal. When a sick bonsai tree is attacked by a fungus, its immune system cannot fight off the disease. It is robbed of its photosynthesis process, brown spots, wiliting and other symptoms occur

To treat the problem of Verticilliosis, The damaged sections of your tree requires careful examination and removal as needed. Get rid of any weeds around the plant. Dead leaves should also be removed and destroyed. Use a mineral-based fungicide to spray the soil, neck, and trunk of your bonsai. And you may want to avoid the excessive use "nitrogenous fertilizers."
Norfolk Island Pine Forest Bonsai Tree - Forest Group  (araucaria heterophila)

Norfolk Island Pine Forest Bonsai Tree - Forest Group (araucaria heterophila)

Open and airy conifer (cone bearing) with light green foliage turning darker with age. One of the best know trees from the South Pacific. Will tolerate warm temperatures and does not even object to dryness, although it does not like glaring sunshine. Decorates well for any holiday or season. Very easy indoor care.

In general, the diseases mentioned here are actually a signal that something is more fundamentally wrong in how you are caring for your Bonsai tree. Re-examine how you are maintaining your Bonsai. A thoughtful review of your practices might keep the problem from re-occuring or from arising in the first place. Are you over watering or over fertilizing? Is your Bonsai getting the right amount of sunlight or shade? Is it well ventilated when inside? Did you Cut back too much on the branches or the roots? Are your tools clean from contamination? Growing a Bonsai tree is an onging education, where one learns from problems to do better in the future.

Organic Fungicides. While copper-based fungicides have been part of the gardener's arsenal for a while, organic fungicides are now available that may work as well and are better for the environment. Check out you local gardening supply store or check out the organic fungicide displayed on this page.

About the Author:  Scott Harker is the publisher of several websites including: Sherlock Holmes Pastiches, Grilled To Perfection - Barbecue, Dieting Help | Move More - Eat Less, and In The Garden.

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