Production of Bacillus thuringiensis integrants

A method for controlling a pest, the method comprising the step of exposing the pest to a pest-controlling effective amount of a pesticidal composition comprising (a) an integrant of Bacillus thuringiensis or spore thereof which produces at least one heterologous crystal delta-endotoxin in said integrant, wherein said integrant is produced by a method comprising the steps of:

• (i) introducing into a cell of a host Bacillus thuringiensis strain a first DNA vector comprising a first origin of replication and at least one functional gene encoding at least one factor required for plasmid replication from said first origin of replication, a second DNA vector comprising a second origin of replication but lacking a functional gene encoding a factor required for plasmid replication from the second origin of replication and a DNA sequence encoding a Bacillus thuringiensis delta-endotoxin, a DNA sequence homologous with a region of the genome of said host strain, and a selectable marker and (ii) culturing the cell of step (i) under selective conditions leading to the loss of the first DNA vector and integration of the second DNA vector into the genome of the host cell by homologous recombination, and (b) a pesticidally acceptable carrier.