Insecticide resistance is defined as which of the following?

• A. Differences in Susceptibility Among Populations of the Same Species
• B. Differences Between Species
• C. Uniform Susceptibility
• D. No Change in Susceptibility

Answer: (A)

Insecticide resistance is about differences in how different populations within the same species respond to the same insecticide. Some groups carry inherited traits that help them survive exposure, such as enhanced detoxification or changes at the insecticide’s target site. When these survivors reproduce, the population shifts toward greater tolerance, so higher doses or different control methods are needed to achieve the same level of control. This concept is distinct from differences between species, which would be interspecific variation, and from uniform susceptibility or no change, which would mean the insecticide remains equally effective across all individuals and over time. In practice, resistance shows up as a shift in the dose–mortality relationship (for example, a higher LD50), illustrating that susceptibility is not the same across all populations of the same species.