What are insect growth regulators (IGRs) primarily used for?

Insect growth regulators (IGRs) are specifically designed to disrupt the normal development and growth processes of insects. They function by mimicking hormones that control insect growth, thereby interrupting the life cycle phases such as molting, pupation, and maturation into reproductive adults. By doing this, IGRs help manage pest populations effectively without the harmful side effects often associated with conventional insecticides. They can prevent insects from reaching maturity, which ultimately reduces their ability to reproduce and infest crops.

The other choices do not accurately reflect the primary purpose of IGRs. Enhancing crop growth, increasing soil fertility, and promoting beneficial insect populations pertain to different agricultural practices and products aimed at improving overall farm productivity or ecological balance, rather than targeting insect developmental processes directly. Therefore, the primary use of IGRs is indeed focused on disrupting insect development, making option B the correct choice.