The pecan nut casebearer, Acrobasis nuxvorella Neunzig, is a severe pest in pecan, Carya illinoinensis (Wang.) K. Koch, orchards in Sonora, México. In this pecan-producing region, severe damage has been quantified in the growth of new shoots at the budbreak time of the pecan trees. To examine the interactions between the pecan nut casebearer and pecan tree, we quantified the hatch of the overwintering larvae at the beginning of the budbreak of pecan trees. The activation of hibernating pecan nut casebearer larvae appears when shoot growth is ≥5cm. The larval development was greatest in shoots >15 cm. A reliable correlation was found between the size of shoots and the larval instars. This is the first study that quantified the emergence of the overwintering larva with budbreak. Information gained was expected to provide basic insight into the behavioral relationship of this herbivore with the host plant.