Invasion of the Caterpillars

I've been on the watch for the white butterflies (moths?) that appear every summer to lay single white eggs on the underside (usually) of Brassica food plants (broccoli, cabbage, Brussels sprouts, etc.). Wikipedia calls them "Small White" butterflies -- though this picture isn't as bright white as the females I see here in North Carolina: (both the following pics from Wikimedia Commons)

This is the caterpillar that hatches from the egg -- up to an inch long. They can shred a plant:

Since I've been seeing the butterflies circling around my Brussels sprouts (and found the single white egg left where I saw one perched on the underside of a leaf), I've been watching for the caterpillars. This was the first one I found two days later:

So I immediately fired up the BioMister and soaked the six plants with BT (bacillus thuringiensis), an organic bacterium that the worms ingest from eating the plants. The bacterium shuts down their appetite (basically) and they expire in a couple days. BT is harmless to humans, animal life, and the environment.