Preventing and Controlling Attacks By Insects

Developing the artistic shape of your bonsai is only one part of bonsai care.  In order to ensure your bonsai health, it is important to provide plenty of light, water, nourishment…and protection from bug infestation!

Most of the time, Insects can be controlled with manual methods; simply pick them off, and squish to prevent unwanted visitors.  If this isn’t possible, always start with natural methods before taking out the chemical warfare.

First and foremost, preventing insects from calling your bonsai home is a simple matter of hygiene.  Keeping your plants well spaced and free from dust is a great place to start, and as bugs tend to attack stressed plants first, be vigilant about making sure that your bonsai are watered properly, nourished well with fertilizer, and given access to the light they crave for proper cell development. 

As an indoor environment usually cannot provide ideal conditions for plants, you may experience an increase in the need for pest control in the winter months.  If one of your plants becomes host to an infestation, be proactive and isolate it from your other plants promptly.  Infested plants can, and will pass on their diseases and bugs to each other just as easily as cold or head lice is passed from child to child in the confines of a elementary school classroom!

Keep a clean and healthy work area in which healthy trees are worked on separately from diseased or infested trees.  Dispose of all infected soil and plant material carefully and be sure to clean all work surfaces well.

If, in spite of your proactive attempts for prevention, you still find that your bonsai has become host to unwanted guests, there are some simple, natural things you can try. Mixing 1 tsp of regular dish soap with 1 quart warm water is a very effective and harmless way to wash those bugs away.  Spray the entire plant, including the under parts of the leaves until desired runoff is achieved. Wait fifteen to 20 minutes and then rinse the plant with clean water to wash residue and bugs down the drain.

In addition to this simple formula, specific pests have some additional treatments which you will find helpful to know about in your efforts to keep your bonsai’s healthy and pest free!

Whitefly- When you move or water your plants and you see what looks like an instant snowstorm of tiny little things flying everywhere, you can be sure that you have a plant infested with the whitefly. These insects multiply like crazy and require immediate action because infested plants will turn yellow, growth will be stunted, and the plant will die. Use a seaweed spray, made out of seaweed powder and water, to mist the leaves of your plants as this will make the leaves undesirable for reproduction. Whiteflies are sometimes indicators of phosphorous and magnesium deficiencies. Correct magnesium deficiencies with a mixture of 4 ounces of Epsom salts to1 gallon of water and soak the soil of the infested plant.

Mealy Bug- One of the most determined bugs in Bonsai, it usually attacks trees that are sick or under stress, which is why if you have a plant with Mealy bugs, you will want to repot your plant, check soil and watering conditions and if weather permits, move your plant outdoors. Mealy bugs tend to hide in the leaf axils, roots or any cool dark place where they can suck the life out of your tree. Mealy bugs are more abundant in late summer and autumn. Mealy Bugs have developed a great protection from spray by coating themselves with a water proof wax. In order to control, dip a small brush in mentholated spirits and dab it on each individual bug which will ensure quick death.

Passion Vine Hopper Nymph- This insect will leave small white tufts on the stem, visible to the naked eye.  The best way to control this insect is to remove host plants from near your bonsai or prune plants well that were previously infested over winter to remove the eggs, and  then burn the clippings. With host plants removed or winter pruned the problems with this insect will be minimal.

Aphids- A common insect that is the favorite dish of the ladybug is also easily controlled with a strong spray of water directed onto the affected area of the plant. The stream will wash the insects off.  Another method is spraying with a soap/oil mixture if the water alone doesn't do the job. Mix 1 tsp. dish soap with 1/2 tsp. Neem oil in 1 quart water in a spray bottle.

Scale- Scale insects come in a bewildering array of shapes and sizes and can quite often go unnoticed until the infestation becomes quite established. They build their protective cap under which they suck the carbohydrates from your tree and lay their eggs. To control scale, spray with an organic mineral oil because this will kill the crawler stage and also blocks the pores in the scales armor which will ensure suffocation.  However, this method will not kill the eggs so you will need to provide more than one application.  Be careful to ensure that your tree will cope with being sprayed with oil because some trees do not like this method.  Another method is to remove them by hand or with a small knife and squish them.

Happy Hunting!

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