Insecticide resistance is defined as a genetic decrease in the susceptibility of an insect population over time, in response to long-term exposure to an insecticide. There is a change in the genetics of a population that allows individuals from a previously sentient population to survive. Resistant populations inherit traits that reduce their sensitivity to an individual insecticide. In other words, pests develop resistance to a chemical through natural selection: the most resistant organisms are those that survive and pass on their genetic traits to their offspring (Miller, 2004). Resistance develops in all agricultural insects and resistant individuals are initially quite rare in pest populations. The development of resistance in fields is influenced by various factors. These include biological and genetic factors. Biological factors are generation time, number of offspring per generation and migration. The genetic factors are the frequency and dominance of the resistance gene, the fitness of the resistance genotype, and the number of different resistance alleles. Genetics and intensive insecticide application are two of several factors responsible for the development of insecticide resistance. Insects with genes conferring resistance to a particular insecticide or class of insecticides survive treatment and are thus “selected” to pass on this resistance to subsequent generations. In an insect population, a few individuals may carry resistance genes. These genes result from mutations and are rare. In the natural environment, the mutant insect is generally weakened, weaker and produces fewer offspring. Upon exposure to insecticides, insects that do not carry the resistance genes die, allowing individuals...... middle of paper ...... distance by assessing their mortality after exposure to a range doses of insecticide and the results compared to those of standard susceptible populations. According to Yu and Nguyen (1992), another method is to use biochemical detection tests to establish resistance by measuring changes in the frequency of resistance genes in field populations under different selection pressures. Many efforts have been made to determine the biochemical or physiological changes that underlie Bt resistance. Diamondback moth has been established to reduce toxin binding to the midgut epithelium as a mechanism of significant resistance (Perez and Shelton, 1996). An immunological method is also available, but only for specific elevated esterases, in collaboration with laboratories with access to the antiserum. There are not yet any monoclonal antibodies available for this purpose..