Damage from the fall armyworm occurs in midsummer. Larvae cut large holes in whorl-stage leaves. Later, large holes may be cut in the stalks at the nodes.
Source of information
J.P. Michaund (http://entomology.k-state.edu/extension/insect-information/crop-pests/corn/fallarmyworm.html)
Pest photo source
J.P. Michaud, Wendy Johnson, KSU Entomology