We had been here about a month before I planted roses out front. The neighbors who garden came by and remarked on how brave I was and didn’t I know about ‘mealy bugs’.
Well the roses have thrived, going on two years now, and the first case of mealy bugs has finally shown up, but on the lemon tree, not the roses. Later they showed up on my black bamboo.
When the orchids get mealy bug, I wash it off, wipe the affected area with rubbing alcohol and spray with an oil.
That would get to be a 24 hour project outside if the mealy bugs do get as bad as I’m told they occasionally do.
Best thing is to cut off affected branches, and spray an insecticidal oil on the plant. I use orange oil. The stores don’t keep the orange oil with the other insecticides. They keep it in with the organic supplies in the house plant section. So you’ll have to hunt a bit to find it. Stock up when you find it too. It is not always kept in stock.
On the bamboo I just blast them off with the garden hose as needed. Mealy bugs will hide if they spot you coming so be sure to sneak up on the little darlings.
Insecticidal soaps are also a good option when dealing with mealy bugs.
(* Note: there is a mealy bug leaf hopper which also looks just like this. Hard blasts of water also work for it. )
Mealy Bug at Answers.com