What is BT and is it harmful to other insects?

Question

I have read various places, that to control caterpillars in the garden, an insecticide with "BT" should be used.

Answer 1

Here is a great website that describes it (too much to put here)

http://www.ipm.ucdavis.edu/PMG/GARDEN/CONTROLS/bacillusthuring.html

An excerpt about BT (Bacillus thuringiensis), and there is more on the link...

Bacillus thuringiensis kurstaki

Type
Microbial insecticide.

Plant uses
Ornamentals, fruit trees, vegetables.

Pests controlled
Leaf- or bud-feeding caterpillars (the larvae of moths and butterflies). Smaller larvae are more susceptible; caterpillars must eat treated plant surfaces to be killed.

Answer 2

BT (Bacillus thuringiensis) is a type of bacterium that kills leaf eating caterpillars. It effects the caterpillar's digestive system and eventually kills them. It is not harmful to other insects, humans or pets. The BT must be consumed by the caterpillar in order to be effective, so be sure to apply it when the caterpillars are present, as it has little residual effect. All parts of the plant leaves, especially the undersides, should be thoroughly covered. And as always, follow the instructions as directed on the product container.