Bacillus thuringiensis (Bt) is a sporulating, Gram-positive facultative-aerobic soil bacterium. Its principal characteristic is the synthesis,
during sporulation, of a crystalline inclusion containing proteins known as δ-endotoxins or Cry proteins. These proteins have insecticidal
properties. The considerable diversity of these toxins, their efficacy and their relatively cheap production have made Bt the most widely used
biopesticide in the world. It is used in the fight against many agricultural crop pests – mostly lepidopteran and coleopteran larvae – notably in
the creation of new plant varieties expressing Bt cry genes. For human health, Bt can be used for the effective control of populations of several
dipteran disease vectors. The aim of this review is to provide an overview of the use of Bt for crop protection and to deal with the problem
of the emergence of insects resistant to this biopesticide. We will begin by presenting various aspects of the biology of this entomopathogenic
micro-organism, focusing on the diversity and mode of action of the insecticidal toxins it produces. We will then present several examples of
utilization of commercially available Bt products used as sprays or as transgenic crops. Finally, we will describe the principal strategy for the
use of Bt transgenic plants, developed so as to prevent or delay the emergence of resistance in target insect populations