sbl

I just wanted to add a little to Bob's suggestion of BT (Bacillus thuringiensis). It is a bacteria that is effective on all larvae of butterflies or moths, but is harmless to all other animals (although I think there is a version that is used for mosquitos).

In general, it is good to avoid pesticides that might kill beneficial insects, so using a bacteria that has a narrow target range is always a good idea.