Beginner

Scientific Name
Spodoptera frugiperda

Identification

• Fall armyworm larvae are pale green to tan (sometimes darker) with a solid dorsal stripe.
  
• The head is dark brown with a distinct white inverted “Y” marking.
  
• Adults have mottled grey forewings and grey/white hindwings; they have a 3.5- 4 cm (1 ½ in.) wingspan.
• The eggs are laid in masses of 150 and are covered in hair.
  
• Larvae generally enter the cob through the side of the husk, but may enter through the silk and cause large, jagged holes that are difficult to miss.

Often Confused With
Common armyworm
Corn earworm

Period of Activity
Fall armyworm are migratory pests. They usually arrive in Ontario slightly later than the corn earworm, which arrive in mid-to-late July, or earlier, depending on the season.

Scouting Notes
Monitor sweet corn fields for fall armyworm from late-July onwards. Examine a minimum of 10 sets of 10 plants per field.

Fall armyworm can also be monitored using a Uni-trap and a pheromone bait. Place a vapona strip in the bucket of the Uni-trap to kill the moths. Change the pheromones every second week.

Thresholds
Prior to tassel emergence use a 15% damage threshold. After the corn has reached late-whorl, 5% feeding injury warrants an insecticide application. The following chart can be used to determine if a spray is necessary.

Sequential Sampling Chart
Plants Examined	Spray if > than
5- 25	3
30- 50	4
55- 105	5

 

Advanced

Scientific Name
Spodoptera frugiperda

Identification
Fall armyworm larvae are pale green to tan (sometimes darker) with a solid dorsal stripe.  The head is dark brown with a distinct white inverted “Y” marking.  Adults have mottled grey forewings and grey/white hindwings.  They have a 3.5- 4 cm (1 ½ in.) wingspan.  The eggs are laid in masses of 150 and are covered in hair.  Damage appears as large, jagged holes that are difficult to miss.  They generally enter the cob through the side of the husk, but may enter through the silk. 

Often Confused With
Common armyworm
Corn earworm

Biology
Fall armyworms over winter in the southern United States and Mexico.  Adult moths are carried northwards on weather fronts, arriving in Canada in late August.  Wet weather conditions in the southern US provide a suitable breeding environment.  These conditions, coupled with severe tropical storms result in higher levels of deposition in the mid-west and Ontario.

The moths are nocturnal and egg-laying occurs at night.  After hatching, the larvae feed on corn for approximately 20 days.  In Ontario, fall armyworm complete only one generation per year.

Period of Activity
This pest may arrive in Ontario as early as July, however abundant numbers generally occur in late August through September.  Corn is attractive to the fall armyworm at all growth stages. 

Scouting Notes
Monitor sweet corn fields for fall armyworm from late-July onwards.  Examine a minimum of 10 sets of 10 plants per field.

Fall armyworm can also be monitored using a Uni-trap and a pheromone bait.  Place a vapona strip in the bucket of the Uni-trap to kill the moths.  Change the pheromones every second week.

Thresholds
Prior to tassel emergence use a 15% damage threshold.  After the corn has reached late-whorl, 5% feeding injury warrants an insecticide application.  The following chart can be used to determine if a spray is necessary.

Sequential Sampling Chart
Plants Examined	Spray if larval count exceeds
5- 25	3
30- 50	4
55- 105	5

Management Notes

• Sprays used for corn borer and corn earworm usually control the armyworm as well.