Young larvae are greenish with a dark head and older larvae are mottled with red and brown. Eggs hatch within four days and larvae (caterpillars) go through six instars before pupation. The eggs often look moldy or fuzzy because they are covered with grey scales. Eggs are usually laid in a mass of 100-200 on light-colored surfaces, including fence posts, poles or tree limbs. Droughty conditions favor their development.Ī generation takes about 30 days to complete its life cycle in the summer, and we assume several generations are possible in Iowa. As the common name suggests, larvae can still be active in October. This year, they are more abundant in the Midwest than usual and are causing late-season issues. Multiple migration events are possible each summer, and adults can be found in Iowa from June to August. It can only successfully overwinter in the southern US (Texas and Florida), but the adults are strong flyers and capable of long-distance migration to northern states. Fall armyworm is native to tropical regions in the western hemisphere.

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