Recently, Andalo, et al. (2010) demonstrated that the entomopathogenic nematodes Steinernema arenarium and Heterorhabditis sp. can kill over 80% larvae of fall army worm, Spodoptera frugiperda under both laboratory and greenhouse condition. Read following paper for the information on the effect of entomopathogenic nematodes on fall army worm.
Andalo, V., Santos, V., Moreira, G.F., Moreira, C.C. and Moino, A. 2010. Evaluation of entomopathogenic nematodes under laboratory and greenhouses conditions for the control of Spodoptera frugiperda Ciencia Rural 40: 1860-1866.