It is important to stay on top of pests and diseases that may affect your bonsai to ensure they remain healthy and thrive as opposed to survive. Check them daily for any ill health signs like wilting leaves, yellowing leaves, dead twigs or branches and look for pests like mites, aphids and mealy bug. If you are unsure take a photo and send this to a bonsai club or bonsai forum like wee trees and they will be able to help identify the problem.
Pests like mealy bug can affect the vigour and health of your bonsai so it is important to treat the pests as soon as possible. This could be by hand removal using a cotton bud dipped in mentholated spirits or by cocktail stick. You otherwise can use chemical controls but always read the labels first. For more information on mealy bug visit the Royal Horticultural Society website – Mealybug