Bti is used to control black flies, a real pest around here. Not being bitten is a good thing, but black fly larvae are a prime food for brook trout, so there has to be careful thought about using it in our streams. The kurtstaki strain was used for control of gypsy moths when we were plagued with those critters. But a fungal disease of said moths apparently caught up with the population explosion and, while I see a few gypsy moth caterpillars every year, we've had no massive defoliation here since 1981.