Technical Abstract: Response to temperature and diet are major factors in the potential population growth of Plodia interpunctella Hübner, a damaging pest of many stored products. A population growth model was used to simulate population development on an optimal wheat-based diet and a sub-optimal diet of raisins at 20 to 35°C, using different starting values for initial density and life stage. Predicted population development on the two diets increased with temperature, and growth patterns were similar regardless of starting population levels at temperatures over 20°C. The predicted population levels on raisins were much less than those predicted for wheat diet, with the same general patterns of increasing populations with temperature at each starting density level or life stage. Results show that the intrinsic population dynamics for P. interpunctella even on a sub-optimal diet and at sub-optimal temperatures are such that density can increase rapidly to levels that would cause extensive economic damage.