A model of the flight phenology of the beet armyworm (Spodoptera exigua Hübner) was constructed using a combination of laboratory and field experimentation. The model incorporates the following relationships: 1) developmental rates of immature stages as linear functions of temperature, 2) age-dependent immature mortality rates, 3) age-dependent oviposition rates, 4) age and temperature-dependent adult mortality rates, and 5) adult flight activity as a function of temperature.

The model was used to examine beet armyworm flight phenology by simulating light trap catches. An extensive black light trapping program was conducted at five locations in three climatic regions within central California to provide a total of six data sets for these tests. Results of the simulations were generally favorable. When initialized with early season light trap data, the model was able to predict the patterns subsequently observed for the locations in the San Joaquin and Sacramento valleys, indicating that a good understanding of beet armyworm flight phenology in these regions was incorporated. The model did not reproduce observed patterns of flights in the cool Salinas Valley, however, indicating that one or more of the relationships in the model was not valid under the conditions of this region.