How can the bacteria bacillus thuringiensis be used to control insects in crops since they produce protein crystals that are toxic to the digestive system of insects?

the bacteria bacillus thuringiensis produce protein crystals that are toxic to yhe digestive system of insects.How can these bacteria be used to control insects in crops?
Apply the bacteria to growing plants. Bio technologists have devised a method to utilize Bacillus thuringens to prevent insects on crops. They insert the gene responsible for the protein crystals into the genome of the crop plants and culture the plants. The resultant plants produce the protein crystals by themselves because they contain the gene to do so. An example of the above method is Bt cotton. It is a high grade cotton plant which is naturally resistant to pests as it has been genetically engineered.