Please take note that the 2nd flight of Mamestra configurata is much higher than normal. Larvae of this species exhibit armyworm behavior – larvae move and feed in groups. Visually scan fields for areas of defoliation or seedpod feeding, and search surrounding soil – or better yet flag the location and return at night.

Damage can be extensive on a number of economically important Oregon crops including: MINT, ALFALFA, BELL PEPPERS, CORN, VEGETABLE BRASSICAS, and CANOLA.

Pay special attention to weedy fields – lambsquarters and pigweed are often used as egg-laying hosts.

Outbreaks of this species are rare, but can occur every 6-10 years. The 2010 Willamette Valley outbreak had 2 distinct peaks of very high activity compared to the long term average(grey shaded). Damage from this 2nd generation can occur into early autumn.

Adult moths have prominent white reniform spots (‘kidney bean-shaped’) and an irregular thick, white band near the terminal edge of the wing. There are 2 overlapping generations per year, and adults can fly up to 50 miles from where they originated!

Identifying larvae is difficult because there are different color forms that can vary substantially. Usually present is a yellow-orange line separating the ventral (pale) and dorsal (darker) areas, and the head is tan or light brown. If you find many larvae and need help identifying them, contact me or the OSU Insect ID clinic

  • Scouting recommendations and more info: related blog post, 2018
  • New publication on dispersal patterns and source populations in W. Canada: Erlandson, M., et al. (2019). “Examining population structure of a bertha armyworm, Mamestra configurata (Lepidoptera: Noctuidae), outbreak in western North America: Implications for gene flow and dispersal.” PloS one 14: e0218993.
  • PNW Handbook – Section: Vegetable crop pests – Armyworm