DISEASE CONTROL

The most common diseases to attack bonsai are insects and mold. Insects come in many varieties, most commonly, aphids, fly larvae, caterpillars, mites and scale insects. Aphids can often be washed off with a stream of water; and caterpillars are merely removed by hand. Mites are discouraged by washing the foliage when watering the tree. Scale insects may be scraped from the leaves. Insecticides will work for most pests but may be toxic to some trees. Some common insecticide sprays are Isotox, Sevin, Cygon, Malathion, etc. Mix insecticides as directed (normal dilution) and spray the foliage with a spray bottle. Wear plastic gloves and a respirator when working with these toxic chemicals, spray outside, and do not inhale or ingest the spray. Mix only what you need so you don't have to dump excess chemicals in the drain.

An alternative to try is Safer spray, a soap solution that kills insects but is relatively non-toxic to humans. Mix it as directed, add a teaspoon of rubbing alcohol per gallon, and use it within 20 minutes of mixing for best effectiveness. Even better is Sunspray Horticultural Oil. This is a very refined petroleum oil (not dormant oil spray) that kills almost any pest that is present on the tree when you spray. It is relatively non-toxic, but should not be inhaled. Don't use it on junipers or other trees with a bluish color, because the foliage will turn very green. Pyrethrins (meant for spraying on vegetables) are very safe and work well on aphids, some scale and other insects. In general, avoid the toxic chemicals if you can because they may contribute to causing cancer or other diseases. Keep all chemicals in a locked cabinet away from children.

Mold can attack the foliage or roots of a tree. It is discouraged by letting the foliage dry after watering (by not watering too late at night) and not over watering the tree. Good drainage helps prevent root-rot. Mold can be treated with chemical solutions of Funginex, Benomyl, Captan. These chemicals are potentially carcinogenic (cancer causing) so wear protection and don't allow them to contact your skin, mouth or lungs. Some bonsaists follow a preventative schedule of spraying most of their trees with a solution of a systemic insecticide and fungicide, perhaps three times per year, in spring, mid-summer and before winter storage. This is supplemented by close inspection of the trees when watering and by maintaining the tree's general health with proper soil, sunlight, fertilizer, watering and air circulation. More detailed discussions of pest control can be found in the bonsai texts. If you have a sick tree and do not know what's wrong, it's best to take it to an expert bonsaist or nurseryman for advice rather than spraying chemicals indiscriminately.