Thanks for the advice. I think I'll just get rid of the plant. I have one other with a far less severe attack which I will try to save. I've had all the plants for several years and never had a problem before. Do particular environments encourage mealy bugs more than others?
I've managed to find a spray which claims it helps to reduce the incidence of mealy bugs. I've move the cactus outside away from all the others and have given it a good blast. I'll repeat the process every few days and await the outcome.
