By May of 2019, it was the first time to report fall armyworm, Spodoptera frugiperda (Smith) at Upper Egypt. So, two field experiments were conducted at Nubaria region, Behaira Governorate to find the relationship between population of S. frugiperda larvae and maize grain yield, and to assess yield loss%, voltinism (annual number of generation) and to evaluate the economics of maize under the circumstances of some insecticidal applications. The RCBD with four replicates was used and treatments included two insecticides (methomyl and emamectin benzoate) applied in trinary or binary sequences against fall armyworm. There was a negative correlation between population of S. frugiperda larvae and maize grain yield. Applying methomyl and emamectin benzoate in a trinary sequence produced the highest maize yield; 4.249 and 3.416 t/fed in the 1st and 2nd seasons, respectively. The highest quantitative yield losses were found in untreated check plots; 77.76 and 78.89% in 1st and 2nd seasons, respectively. Methomyl, emamectin benzoate and methomyl sequence produced the highest net benefit over untreated check and net benefit/ total costs (%).The insect pest had 5 generations on maize plants during the growth period from May1st to November 30th in both seasons. To avoid the widespread of fall armyworm, in Egypt, the growers are recommended to spray a sequence of insecticides, including methomyl 15 days after planting, emamectin benzoate, and methomyl at recommended doses with 10 day-interval between each two pesticide applications.