Around 2016, my area experienced massive infestation by armyworm. It seemed to be a national problem since newpapers bear the news. To control them use these insecticides: diazinon (acephate), alpha cypermethrin (pyrethroid), chlorpirifos (organophosphate), diflubenzuron (insect growth regulator), trichlorfon (acephate), chlorantraniliprole (ryanoids, 28), spinetoram (5), emamectin benzoate (avermectin), indoxacarba (oxadiazine) and lambda cyhalothrin (pyrethroid, 3).
And note, spray in the evening so that when they come out at night to feed, the pesticide will get them. Also direct the spray into the leaf funnel, else, you are wasting your pesticide.