Check your supply of fungicides and insecticides. Check your trees every day. Don t wait. Counterattack at the first sign of infestation. Be sure to follow all instructions.
Preventative measurers are helpful in controlling insects.
The area under your benches should be clean no leaves, weeds, puddles, etc. Use a commercial inspect spray under your benches and along the pathways of your bonsai garden. A bonsai is confined to its container. Air, water and nutrients will not be able to penetrate the root ball. The tree will suffer and eventually die without some action being taken.