Investigation on the occurrence and damage of Spodoptera frugiperda in the main maize production areas of Guangxi

【Objective】In order to provide scientific reference for forecast and precision control of fall armyworm, Spodoptera frugiperda in its year-round breeding area and other main maize production regions of China, the population dynamics and damage of fall armyworm in the main maize-growing areas of Guangxi were investigated.【Method】Seven fixed monitoring and investigation points were selected in Chongzuo, Nanning and Hechi in 2020. The number of fall armyworm larvae and its damage characteristics to maize were investigated every 7 d during corn growing season by the diagonal five-point sampling method, the damage rate of plants and the number of larvae per 100 plants were calculated. Every two barrel-shaped traps with sex-induced cores were placed in the seven fixed monitoring and investigation points respectively, then the trapping situation was investigated and recorded every 7 d, the number of fall armyworm adults was counted.【Result】The occurrence of fall armyworm larvae in each investigation point peaked once in spring and autumn respectively. The highest number of larvae per 100 plants in spring and autumn were 35.00 and 64.67 respectively. The number of larvae in autumn was higher than that in spring. The occurrence dynamics of larvae differed from region to region, the larval emergence period in Fusui of Chongzuo, Jiangnan District and Wuming District of Nanning was short and concentrated, the number of larvae per 100 plants and the peak value of the three points were higher. Fall armyworm larvae could damage all growth stages of maize. The seedling stage was damaged mainly by young larvae, while the flowering and maturity stages were damaged mainly by 5^th-6^th instar larvae. Various instar larvae damaged other maize growth periods with overlapped generations. The number of fall armyworm adults in spring showed a parabolic increase trend in each investigation point with a maximum value of 25.33 adults per barrel-shaped trap. The number of adults in autumn fluctuated with a small peak every 21 d, and the maximum value was 34.67 adults per barrel-shaped trap. The number of adults in autumn was generally higher than that in spring.【Conclusion】Fall armyworm can occur throughout the year in Guangxi with no less than seven generations per year. The number of fall armyworm in autumn is obviously higher than that in spring, and the degree of occurrence increases with temperature. Region-specific differences are observed in the occurrence period and number of larvae. Maize can be damaged by fall armyworm larvae at different growth stages. Fall armyworm seriously damages the growth of maize, so the monitoring and forecasting should be strengthened. The prevention and control of young larvae and adults in peak period should be strengthened according to the growth of maize and the regional climate to effectively reduce the damage caused by fall armyworm.