Pacific Northwest Insect Management Handbook

Lentil-Western yellowstriped armyworm

  • Facebook logo
Image related to Lentil-Western yellowstriped armyworm
Western yellowstriped armyworm
Spodoptera praefica Grote
Young immature showing damage on leaves
© Ken Gray Insect Image Collection
Image related to Lentil-Western yellowstriped armyworm
Western yellowstriped armyworm
Spodoptera praefica Grote
Egg(s) on host
© Ken Gray Insect Image Collection
Image related to Lentil-Western yellowstriped armyworm
Western yellowstriped armyworm
Spodoptera praefica Grote
Adult
© Ken Gray Insect Image Collection

Spodoptera praefica

Pest description, crop damage and life history

See:

Common Pests of Vegetable Crops

Pest monitoring Monitoring to catch infestations early is important, because Bacillus thuringiensis (Bt) insecticides work much more effectively on small larvae.

Management-biological control

Common natural enemies of armyworms include several braconid and ichneumonid wasps and many general predators, including assassin bugs, damsel bugs, spiders, and a nuclear polyhedrosis virus, reported to have brought about excellent late year control in Canada. None of these natural enemies can be counted upon to achieve adequate control in any given year.

Management-cultural control

Weed control is important. Lambsquarters and wild mustard attract egg-laying females and provide a source of food for larvae. As weeds dry, large populations of armyworms can move onto crops. When infested alfalfa fields are mowed, large dispersions of armyworms also can take place. Fall tillage can help destroy overwintering pupae.

Management-chemical control: HOME USE

Apply any one of these materials to the soil surface at first sign of cutworm activity. Consult label. Minimum preharvest interval (PHI) varies with crop.

  • azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
  • carbaryl
  • plant-derived essential oils (rosemary, peppermint etc.)-Some formulations are OMRI-listed for organic use.
  • pyrethrins-Some formulations are OMRI-listed for organic use.

Management-chemical control: COMMERCIAL USE

  • alpha-cypermethrin (Fastac EC) at 0.017 to 0.025 lb ai/a. PHI 1 day for succulent, 21 day for dried shelled lentils. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.075 lb ai/a per season.
  • azadirachtin (Neemix 4.5) at 0.14 to 0.35 lb ai/a. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • Bacillus thuringiensis (Javelin) at 0.12 to 1.5 lb/a. PHI 0 days. REI 4 hr. Acts slowly; may need multiple applications. Add an appropriate spreader-sticker to enhance control. Most effective on small larvae. Some formulations OMRI-listed for organic use.
  • beta-cyfluthrin (Baythroid XL) at 0.019 to 0.025 lb ai/a. PHI 7 days. REI 12 hr. Do not exceed 0.05 lb ai/a per season. Do not feed treated vines or hay to livestock. Retreatment interval 14 days.
  • beta-cyfluthrin/imidacloprid (Leverage 360) at 0.056 to 0.066 lb ai/a. PHI 7 days. REI 12 hr. Retreatment interval 14 days. Do not exceed 0.05 lb ai/a beta-cyfluthrin or 0.1 lb ai/a imidacloprid per season. Effective on first and second instars.
  • bifenthrin (Brigade 2EC) at 0.033 to 0.1 lb ai/a. PHI 14 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.3 lb ai/a per season.
  • bifenthrin (Capture LFR) at 0.39 to 0.49 oz ai/1,000 ft row at planting. REI 12 hr. Do not exceed 0.1 lb ai/a per season as an at-plant application. Some formulations are
  • bifenthrin/imidacloprid (Brigadier) at 0.0875 lb ai/a. PHI 14 days. REI 12 hr. Do not exceed 0.13 lb ai/a imidacloprid and 0.13 lb ai/a bifenthrin. Retreatment interval 7 days.
  • bifenthrin/zeta-cypermethrin (Hero EW) at 0.04 to 0.1 lb ai/a. PHI 21 days. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.266 lb ai/a per season.
  • carbaryl (Sevin 4F) at 1 to 1.5 lb ai/a. PHI 14 days of grazing 21 days harvest for dry lentils. Retreatment interval 7 days. REI 12 hr. Do not exceed 6 lb ai/a per season. Limit 4 treatments.
  • Chromobacterium subtsugae (Grandevo) at 0.3 to 0.9 lb ai/a per 100 gal. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • cyfluthrin (Tombstone) at 0.038 to 0.05 lb ai/a. PHI 7 days. Retreatment interval 14 days. REI 12 hr. Do not exceed 0.1 lb ai/a per season. Do not feed vines or hay.
  • gamma-cyhalothrin (Declare) at 0.01 to 0.015 lb ai/a. PHI 21 days. REI 24 hr. Do not exceed 0.06 lb ai/a per season. Retreatment interval 5 days. Do not graze or harvest for feed. An oil or nonionic surfactant improves performance.
  • lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/a. PHI 21 days. REI 24 hr. Retreatment interval 5 days. Do not exceed 0.12 lb ai/a per season. Do not graze or harvest for feed.
  • methomyl (Lannate SP) at 0.45 to 0.9 lb ai/a. PHI 21. REI 48 hr. Do not exceed 0.9 lb ai/a per season. Limit 2 applications per year.
  • methoxyfenozide (Intrepid 2F) at 0.06 to 0.12 lb ai/a early season and 0.12 to 0.25 lb ai/a mid season and 0.16 to 0.25 lb ai/a late season. PHI 7 days. REI 4 hr. Retreatment interval 7 days. Limit 4 treatments per year. Do not exceed 1 lb ai/a per season.

Kaur, N. (Ed.). 2024 Pacific Northwest Insect Management Handbook.
© Oregon State University.

Use pesticides safely!

  • Wear protective clothing and safety devices as recommended on the label. Bathe or shower after each use.
  • Read the pesticide label—even if you’ve used the pesticide before. Follow closely the instructions on the label (and any other directions you have).
  • Be cautious when you apply pesticides. Know your legal responsibility as a pesticide applicator. You may be liable for injury or damage resulting from pesticide use.

Trade-name products and services are mentioned as illustrations only. This does not mean that the participating Extension Services endorse these products and services or that they intend to discriminate against products and services not mentioned.