I'm battling mealy bugs now...in my experience, those are more devastating than caterpillars or aphids.
Left unchecked, they will literally suck the life out of a plant and very quickly.[/quote]
Mealy bugs running rampant have made me have to pitch several hibiscus and several different cacti when I couldn't get them under control. Vigilance is the only way to go. Catch them when there are few of them and nip them out right then.