The grape berry moth, Endopiza viteana (Clemens) feeds on wild and cultivated Vitis spp., causing economic damage in the latter. We studied incidence of pheromone trap catch data, and combined this with previous work on development and diapause to construct a comprehensive model of the temporal dynamics of E. viteana. We explored the behavior of this model in six eastern United States locations along Lakes Erie and Michigan, the Finger Lakes in New York, and in Missouri and Virginia. Voltinism of E. viteana is influenced by the accumulated growing degree-days before the postsummer solstice photoperiod at which eggs develop exclusively into diapausing pupae. Our model generally predicted two full and a partial third generation in Geneva, NY, whereas partial fourth generations existed in vineyards along Lakes Erie and Michigan. In more southern latitudes, such as Missouri and Virginia, the absence of a partial fourth generation would be rare. Also, our model suggested the presence of clinal latitudinal variation in diapause induction, with southern populations of E. viteana responding to shorter daylengths than northern populations. These predictions, based on average 10-yr surface temperatures (1991–2000), are supported by past observations and explain the variability in voltinism from year to year that has been reported in the northeastern United States and Niagara Peninsula of Canada.