Background
Fall armyworm get their name from the the mass exodus they take after depleting an area of foliage. Armyworm will “march” in a giant black mass to their next food source.
Armyworm feed mostly on grasses and small grain crops including oats, rye, wheat and corn.
Damage
In wheat, oats, and rye, armyworm will move up the plant eating the leaf margins, and eventually the flag leaf and kernals. Often, the most notable sign of infestation are stems clipped just below the heads.
In corn, larvae may leave the plant bare after striping the entire leaf.
During epidemics, it is possible to hear the crunching of larvae eating at night.
Life cycle
Armyworm overwinter south of Michigan. During the early spring adults fly north and lay eggs at the base of plants. Within one to two weeks larvae hatch and begin feeding on host plants at night. During the day, larvae are found in the top three centimeters of the soil and under plant residue.
In mid-summer a second generation emerges. Sometimes a third generation will surface in late August or early September.
Scouting
Scouting in corn is difficult because larvae only feed heavily at night.
In wheat, grab a bunch of plants and shake them vigorously over bare ground and count larvae that fall. Economic threshold is six larvae per square foot, although it is recommended to take action if a considerable number of heads are found clipped per square foot.
Armyworm
Background
Fall armyworm get their name from the the mass exodus they take after depleting an area of foliage. Armyworm will “march” in a giant black mass to their next food source.
Armyworm feed mostly on grasses and small grain crops including oats, rye, wheat and corn.
Damage
In wheat, oats, and rye, armyworm will move up the plant eating the leaf margins, and eventually the flag leaf and kernals. Often, the most notable sign of infestation are stems clipped just below the heads.
In corn, larvae may leave the plant bare after striping the entire leaf.
During epidemics, it is possible to hear the crunching of larvae eating at night.
Life cycle
Armyworm overwinter south of Michigan. During the early spring adults fly north and lay eggs at the base of plants. Within one to two weeks larvae hatch and begin feeding on host plants at night. During the day, larvae are found in the top three centimeters of the soil and under plant residue.
In mid-summer a second generation emerges. Sometimes a third generation will surface in late August or early September.
Scouting
Scouting in corn is difficult because larvae only feed heavily at night.
In wheat, grab a bunch of plants and shake them vigorously over bare ground and count larvae that fall. Economic threshold is six larvae per square foot, although it is recommended to take action if a considerable number of heads are found clipped per square foot.
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