Stomach and midgut insecticides are one of five classes of insecticides. They come from microbes. Some microbes release toxic compounds. When some insects eat these microbes, they get poisoned. Their stomach is the part of their body affected.
Bt or Bacillus thuringiensis belongs to this class of stomach and midgut insecticides.
Bt is commonly used in organic gardens to control herbivore insects such as the white cabbage moth larvae on brassicas such as broccoli and cauliflower. This is a common bacteria found in the soil. It also occurs naturally in the gut of various types of caterpillars, in animal faeces, aquatic environments, leaf surfaces and grain storage facilities.
Bacillus sphaericus is an insecticide used to control mosquitoes.
Read the fifth and final blog in this series: unknown and multi-site insecticides.