When working to prevent the possible injury or death of your beloved bonsai, the best defense is a strong offense: be vigilant by keeping your bonsai clean, dust and debris free and cleared of fallen leaves and flowers; be sure sufficient lighting is supplied, as well as, good ventilation and lots of fresh air. A healthy bonsai is without a doubt the most important preventative of pests and disease.
Unfortunately, even the most observant bonsai enthusiast is likely to encounter some type of pests or disease during their endeavors.
It is healthier for your bonsai to be treated for pests and diseases in incremental steps of increasing toxicity.
The first thing to try to change is your bonsai’s current environment (the simplest and safest technique).
The second incremental step would be to try, if possible, to introduce biological controls such as ladybugs (are of no danger to your bonsai and they will eat nearly all pests).
The third incremental step would be to use chemicals, also in levels of increasing toxicity. To start, you can try spraying a very mild solution of warm water and liquid dish soap on your trees.
The fourth incremental step would be to try using a mild insecticidal soap such as the brand name: Safer (offers effective control over most pests).
The incremental step of Ã¢â‚¬Å“last resortÃ¢â‚¬Â would be to use an actual Ã¢â‚¬Å“chemicalÃ¢â‚¬Â spray, such as: Schultz’s insecticide.