Close
Home >

Scouting for Fall Armyworm

 
817820D9-64E5-90C1-236D-3EEF086F28A1

Scouting for Fall Armyworm

In-Depth Downloads

Pest Importance

  • Fall armyworm, Spodoptera frugiperda, is a minor pest of corn in the United States.
  • Economic damage is sporadic from year to year.
  • Fields at highest risk from injury are:
     
  1. Fields planted to non-Bt hybrids without Lepidoptera control
  2. Fields in the southern U.S. and Texas
  3. Late-planted fields
  4. Late-maturing hybrids
 
Early-stage fall armyworm larva
Early stage fall armyworm larva
 

Injury Symptoms in Whorl-Stage Corn

  • Early stage larval feeding:
    • Causes “windowpane” and shot holes in leaves
  • Late-stage larval feeding:
    • Causes elongate, ragged holes (see photo below)
    • May cut leaves in half
    • Injures developing tassel in VT stage
    • Plugs whorl with wet, yellowish-brown frass
Whorl-stage corn injury from fall armyworm
Whorl-stage corn injury from fall armyworm
 

Scouting for Fall Armyworm

  • Only larvae in whorl-stage corn can be controlled with insecticides; larvae in corn ears are protected
  • Scout for larvae in whorl-stage corn:
     
  1. Select 20 consecutive plants in a row.
  2. Inspect plants for feeding injury.
  3. Confirm identity of pest species as fall armyworm.
  4. Repeat 20-plant sample at 4 additional locations.
  5. Determine percent infestations based on 100 plants.
  6. Consider insecticide application when 20% of whorl-stage plants are infested with live larvae.

Identification of Fall Armyworm

Dark spots (tubercles) on dorsal surface arranged in "trapezoid" or when near the tail, in a "square" pattern. Spots are darkened in photo for emphasis.

Fall armyworms can be distinguished from similar corn caterpillars by 2 physical characteristics:

  1. Inverted “Y” pattern on the front of a dark head (see next 2 photos)
  2. Dark spots (tubercles) on dorsal surface arranged in “square” or “trapezoid” pattern (see third photo)

 
Similar caterpillar species found on corn (armyworm, fall armyworm and corn earworm.)
Similar caterpillar species found on corn (left-right): armyworm, fall armyworm
and corn earworm. The fall armyworm has an inverted "Y" pattern on the front of a dark head.
 
An inverted “Y” pattern on the front of a dark head identifies the fall armyworm.
An inverted "Y" pattern on the front of a dark head identifies the fall armyworm.
 

Fall armyworm caterpillar on corn ear.
Dark spots (tubercles) on dorsal surface arranged in "trapezoid" or when
near the tail, in a "square" pattern. Spots are darkened in photo for emphasis.

 

Photos and Text
Marlin E. Rice; Reviewed by Susan Moser, Herb Eichenseer and Laura Higgins

Reference
Bessin, Ric. 2003. Fall armyworm in corn. University of Kentucky Cooperative Extension Service. ENTFACT-110.

FFEDE9CF-8883-3457-2F80-9CB62F350598