Maize is a major cereal crop worldwide, and its stable production is essential for national and global food security. Pests are among the key factors affecting the yield and quality of maize. Therefore, it is crucial to evaluate the yield recovery and quality losses after implementing control measures against pests during different periods. In this study, we investigated the population dynamics of the main maize pests in South China and assessed the yield and quality of maize treated with measures for the effective control of these pests during different periods. The results showed that the fall armyworm (FAW), Spodoptera frugiperda, was the most severe pest of autumn maize. There was a 10.02% decrease in ear weight when no control measures were taken at the fourth-leaf stage, and there were 80.45% and 76.09% increases in the damage index when no control measures were taken at the tasseling and blister stages, respectively. Additionally, the tannin content in maize kernels increased by 26.28% when no pest control measures were taken throughout the entire growing period. These findings will increase farmers’ knowledge regarding the detrimental effects of the FAW and provide a theoretical basis for the reasonable and timely control of maize pests.