BT has to be used cautiously, never broadcast, because it does impact the butterfly population. It is used to kill caterpillars that destroy garden plants, and needs to be applied carefully. There is a BT, israelensis, that is excellent when added to water to kill mosquito nymphs and is not harmful to butterflies. There are, I suspect, lots of kinds of nematodes, beneficial and otherwise. There was no endorsement of those products listed for the entire world; they are what are used here in the lower Great Plains of the U.S. Follow the Dirt Doctor link for more information.

SRS