Mealy bugs are up to 1/4-inch long and covered in white fluff or powder. They tend to congregate on the young stems and the undersides of jade plant leaves. Mealy bugs also hide in the crevices formed where jade plant leaves meet their stems. Check the ground underneath your jade plant for signs of white powder, which is a sign of hidden mealy bugs. If your plant is watered correctly and receives fertilizer but is still looking sick, remove it carefully from its container and check the roots for mealy bugs.
Dip a paint brush or cotton swab in a 70% solution of rubbing alcohol (isopropyl alcohol) and rub each mealy bug. Repeat the process every day until all the bugs are dead. Do not spray a jade plant with a rubbing alcohol solution as this will poison the plant.
Test insecticidal sprays on a small section of your jade plant before use as some can kill the leaves. Do not use insecticidal soap sprays or sprays containing malathion or pyrethrins on jade plants. Treat heavy infestations of mealy bugs on jade plants with a systemic insecticide drench containing dimethoate or midacloprid. This is taken up by the plant's roots and poisons the bugs as they feed. A soil drench will also treat mealy bugs on the roots.
Do not re-pot jade plants into peat-based compost as this is quite open and allows mealy bugs to colonize the roots. Take pest-free cuttings from severely infested plants and discard the parent if the infestation cannot be cured.