Imidacloprid is a good one for general knock-down, and it's not too environmentally unfriendly. You might want to read more about it:
Another alternative to a pure "poison" is an insect growth regulator, kinoprene, which is available as Enstarr II on the market.
The big advantage of an IGR over a poison is that there can be no resistence development, as with poisons. Picture this: you spray with poisons, and most of the insects are killed. Their larvae might
be, and their eggs are probably untouched. However, the exposure to the toxin might develop a change in the genetics of the survivors that leads to resistance to the poison, and we're left with hard-to-kill super bugs that can pass those traits onto their offspring.
An IGR, by contrast, prevents the insects - in all stages - from maturing. No maturation = no offspring = no resistance and eventual death.
I prefer a multi-prong approach, so when I see an outbreak of something, usually coming in with new plants, I spray the entire collection with a poison (I use Orthene), and IGR (Enstar II) and an antifeedant (neem oil plus liquid soap to emulsify it) all at once. The poison kills most of the adults, the IGR prevents the maturation of more of them, and the antifeedant discourages migration to other plants. Repeat that weekly for three treatments, and you'd be amazed at the effectiveness.
DO NOT spray insecticides as a preventive treatment, as that's where most resistance is developed. IGR's on the other hand, may be used that way with no issue, and the neem oil is a good, general repellant that's also a leaf shine!