Once seedlings emerge or right after transplanting, check plants at least twice per week for armyworm egg masses and young larvae.

Consider placing out pheromone traps (delta, wing, or bucket type) along field edges to monitor adult flights and predict egg laying.

If numbers are high on weeds, watch carefully for infestations on crop seedlings.

Check for egg masses and young larvae on pigweeds, lambsquarters, nettleleaf goosefoot, and other nearby weeds.

Fields smaller than 40 acres may require fewer samples.

Check at least 25 plants in each quadrant of a 40- to 80-acre field.Chenopodium species (e.g., lambsquarters, goosefoot) are particularly attractive to beet armyworm larvae.īegin monitoring for beet armyworm twice per week even before seedlings emerge. Weeds can be pulled and readily examined whereas cilantro and parsley are often brittle and easily damaged during the early morning and late evening hours when larvae are active. Beet armyworm eggs and larvae are often easier to find on weeds in and near the field than in cilantro or parsley. Monitor fields frequently for beet armyworm from planting until harvest. Seedlings are susceptible to armyworm damage. Beet armyworms numbers grow as weather warms and are most common on late summer and fall crops. Although newly emerged adults can be found throughout the year in central and southern California, major emergences and migration flights are usually observed in the spring through late summer. The pupal stage persists 7 to 10 days but may be much longer when temperatures are cooler. After five to six instars, the larvae burrow into the soil to pupate. Large larvae generally shelter in the center of the plant or underground during daylight hours. The larval stages last from 2.5 to 3 weeks at 70° to 80☏. The body surface is smooth and almost hairless. Often there is a dark spot on the side of the body just above the second true leg. Older larvae vary in color but are usually a shade of olive green to black with many fine, wavy, light-colored broad stripes down the back on each side and may be up to 1.5 inches long. When eggs first hatch, the pale green 1/16 inch (1.5 mm) long larvae feed for first few days in groups near the egg mass, skeletonizing or completely consuming leaves.Īs the larvae age, they disperse and move toward the center of the plant and feed singly.

Adult moths lay 20 to 400 eggs in mass that they cover with their own light-colored scales, giving the masses a distinctive cottony appearance.

Beet armyworm adults are 1/2 to 3/4 inch, nondescript brown moths.

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