Colorado potato beetles, in the adult stage, spend the winter several inches underground. They emerge in spring, along with the first potato shoots. They mate, lay eggs and die. Four to nine days later small reddish larvae hatch and attack potato leaves. Two to four weeks later they move into the soil, make a cell and are transformed into a yellow pupal stage which lasts about a week.
Adults then emerge and lay eggs for a second generation.
Cultural practices such as tilling before the last freeze of winter also help keep the insect population in check. Tilling at this time turns up insects and exposes them to killing temperatures. It also disrupts tunnels in the soil, leaving some overwintering insects with no way out. When starting a garden in a new spot, break the ground in the winter or early spring if the site is not prone to erosion. Ground that has not been tilled in a long time, such as old pastures and lawns, can harbor lots of cutworms, grubs and other insects.