Two major pests cause damage of economic importance to maize crops in France: the European corn borer (Ostrinia nubilalis), which has a worldwide distribution, and the pink maize stalk borer (Sesamia nonagrioides), which is present all around the Mediterranean. During winter, last instar larvae of these species exhibit a facultative diapause. Early forecasting of the field emergence period and a good knowledge of the overwintering survival (both strongly dependent on conditions controlling diapause maintenance and termination) are key features for effective management of these pests. In this connection physiological studies of diapause provide us with useful information. Special emphasis is given to variations of carbohydrate metabolism, particularly glycogen, trehalose and glycerol in both species. In the European corn borer the presence of glycerol and trehalose makes it possible to forecast diapause termination 2–3 months before the first field pupal molts. These data are used for the construction of a model of the population dynamics, developed by the National Institute of Agronomic Research. In the pink maize stalk borer we demonstrate the great sensibility of this pest to low temperatures, and we propose a novel cultural pest-suppressing method which is now being tested in collaboration with the General Association of Maize Producers.