Spotted wing drosophila (Drosophila suzukii Matsumura) is an important pest of berry crops like strawberry, brambles (raspberry, blackberry, others), elderberry, blueberry, cranberry (including lingonberry), and Ribes (currant and gooseberry). The insect is important because, unlike other drosophilids, it can directly damage soft fruit crops by laying its eggs in the berries and fruits that can go undetected during its initial damage. Degree-day models have been incorporated in the successful management of many key pests of small and tree fruits such as codling moth (Borchert et al. 2004, Jones et al. 2013), plum curculio (Akotsen-Mensah et al. 2011), and brown marmorated stink bugs (Nielsen et al. 2008, 2016), but this has not been done for SWD in Missouri. A trap-based predictive model is an important pest management tool that could be used to detect and predict SWD early activity in the field to help in the timely application of insecticides (Drummond et al. 2019, Kamiyama et al. 2020). The phenology and seasonal patterns of SWD were investigated during 2021-2022 in several research and grower farms in Missouri. A relationship between trap numbers and degree day accumulation during the period was examined using logistic and Weibull functions to predict the activity of SWD. The results showed a logistic function as a better predicting function for the SWD phenology. The results are discussed based on the reliability of the model in predicting SWD seasonal activities.