Pacific Northwest Insect Management Handbook

Field and silage corn-Armyworm

  • Twitter logo
  • Facebook logo
Image related to Field and silage corn-Armyworm
Beet armyworm
Spodoptera exigua Hubner
Immature female adult
© Ken Gray Insect Image Collection
Image related to Field and silage corn-Armyworm
Beet armyworm
Spodoptera exigua Hubner
Egg(s) on host
© Ken Gray Insect Image Collection
Image related to Field and silage corn-Armyworm
Beet armyworm
Spodoptera exigua Hubner
Adult
© Ken Gray Insect Image Collection

Includes

Armyworm (Pseudaletia unipuncta)
Beet armyworm (Spodoptera exigua)

Pest description and crop damage Mature larvae are 1.5 inches long. Color varies from brown (armyworm) to green. Moths occasionally are attracted to weeds in corn fields.

Management-chemical control

For best results, apply treatments when armyworms are small to medium size (0.25 to 0.75 inch).

  • alpha-cypermethrin (Fastac CS) at 0.02 to 0.025 lb ai/a. REI 12 hr. PHI 30 days grain and stover; 60 days forage. Retreatment interval 3 days. Do not exceed 0.075 lb ai/a per season.
  • Bacillus thuringiensis (Javelin) at 0.12 to 1.5 lb/a. PHI 0 days. Use according to individual manufacturer's label instructions. OMRI-listed for organic use.
  • beta cyfluthrin (Baythroid XL) at 0.013 to 0.022 lb ai/a. PHI 0 days for green forage and 21 days for grain or fodder. REI 12 hr. Do not exceed four applications or 0.088 lb ai/a per season.
  • bifenthrin (Brigade 2EC, Sniper, Capture LFR) at 0.033 to 0.1 lb ai/a foliar, 0.04 lb ai/a preemergence, or 0.047 to 0.062 lb ai/a preplant incorporated. PHI 30 days for harvest, grazing, or cutting for feed. REI 12 hr. Do not apply more than 0.3 lb ai/a per season. Do not apply Capture LFR as foliar treatment.
  • bifenthrin/indol butyric acid (Empower 2) at 0.04 to 0.1 lb ai/a. PHI 30 days. REI 24 hr. Do not exceed 0.3 lb ai/a including foliar and at planting.
  • bifenthrin/zeta-cypermethrin (Hero EW) at 0.04 to 0.1 lb ai/a foliar or at planting. PHI 30 days grain and stover; 60 days forage. REI 12 hr. Do not graze for 30 days after treatment. Do not exceed 0.4 lb ai/a per season.
  • Burkholderia spp. (Venerate XC) at 1 to 4 qt/a. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • carbaryl (Sevin 4F) at 1 to 2 lb ai/a. PHI 14 days for forage or silage grazing, and 48 days for grain harvest. REI 24 hr. Do not exceed four applications or 8 lb ai/a per season. Latex-based formulations, such as Sevin XLR Plus, are less hazardous to bees.
  • chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.052 to 0.08 lb ai/a. PHI 21 days. REI 24 hr. Do not exceed 0.12 lb ai of lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole per acre per growing season. Retreatment interval 7 days.
  • chlorantraniliprole (Coragen) at 0.045 to 0.098 lb ai/a. PHI 14 days. REI 4 hr. Do not exceed 4 treatments or 0.2 lb ai/a per season. Retreatment interval 7 days.
  • chlorpyrifos-
    • Lorsban 15G at 0.056 to 0.075 lb ai/1,000 row ft (post-plant). PHI 21 days. REI 24 hr. Do not exceed 0.15 lb ai/1,000 row ft or 3 lb ai/a per season. Apply as a band or treatment.
    • Lorsban Advanced at 0.47 to 0.94 lb ai/a post emergence broadcast. Chemigation permitted. PHI 21 days grain, ears, forage or fodder. REI 24 hr. Limit 3 treatments. Do not exceed 3 lb ai/a per season. RESTRICTED USE IN OREGON.
  • 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 0.025 to 0.044 lb ai/a. PHI 0 days for green forage and 21 days for grain or fodder. REI 12 hr. Retreatment interval 7 days. Do not exceed four applications or 0.175 lb ai/a per season.
  • deltamethrin (Delta Gold) at 0.018 to 0.022 lb ai/a. PHI 21 days for grain or fodder, and 12 days for forage or grazing. REI 12 hr. Do not apply more than 0.095 lb ai/a per season. Retreatment interval 21 days. Limit 5 treatments per year.
  • esfenvalerate (Asana XL) at 0.03 to 0.05 lb ai/a. PHI 21 days. REI 12 hr. Do not exceed 0.25 lb ai/a per season.
  • gamma cyhalothrin (Declare) at 0.01 to 0.015 lb ai/a. Effective on first and second instar larvae only. PHI 1 day for grazing and forage, or 21 days for fodder and silage. REI 24 hr. Do not exceed 0.06 lb ai/a per season.
  • GS-omega/kappa-Hxtx-Hv1a (Spear Biological Insecticide) at 0.8 lb ai/a. PHI 0 day. REI 4 hr. Do not exceed 2 lb ai/a per year.
  • indoxacarb (Steward EC) at 0.059 to 0.11 lb ai/a. PHI 14 days grain, 1 day forage, fodder, silage. REI 12 hr. Limit 2 treatments. Do not exceed 0.22 lb ai/a per year.
  • lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/a. PHI 21 days. REI 24 hr. Do not apply more than 0.12 lb ai/a per season, 0.06 lb ai/a after silk initiation, or 0.03 lb ai/a after milk stage.
  • methomyl (Lannate SP) at 0.22 to 0.45 lb ai/a. PHI 21 days for ears, 3 days for forage, 21 days for fodder. REI 48 hr. Do not exceed 2.25 lb ai/a or 5 treatments per season. Retreatment interval 5 to 7 days.
  • methoxyfenozide (Intrepid 2F) at 0.06 to 0.25 lb ai/a. PHI 21 days. Do not exceed 1 lb ai/a per season. REI 4 hr.
  • methoxyfenozide/spinetoram (Intrepid Edge) at 0.094 to 0.281 lb ai/a. PHI 28 days. REI 4 hr. Do not exceed 0.625 lb ai methoxyfenozide and 0.125 lb ai spinetoram per acre per year. Limit 3 treatments. Retreatment interval 4 days except 2 days for silking.
  • permethrin-
    • Ambush 25W at 0.1 to 0.2 lb ai/a foliar or as preemergent. PHI 0 days for forage; 30 days for grain harvest or fodder. REI 12 hr. Allow 6 days between applications. Do not apply more than 0.6 lb ai/a per season.
    • Loveland Permethrin Cutworm Bait at 0.1 to 0.15 lb ai/a. REI 12 hr. PHI 0 days for forage; 30 days for grain harvest or fodder. Retreatment interval 7 days. Do not exceed 0.45 lb ai/a per season.
    • Pounce 1.5G at 0.0075 to 0.015 lb ai/1,000 row ft soil or 0.1 to 0.15 lb ai/a broadcast. PHI 0 days for forage; 30 days for grain harvest or fodder (stover). REI 12 hr. Apply in furrow or as band at planting. Retreatment interval 7 days. Do not exceed 0.45 lb ai/a per season.
  • spinetoram (Radiant SC) at 0.023 to 0.047 lb ai/a. PHI 3 days forage or fodder; 28 days grain. REI 4 hr. Do not exceed 0.125 lb ai/a per year. Do not exceed 3 treatments. Retreatment interval 4 days.
  • spinosad (Success) at 0.023 to 0.094 lb ai/a. PHI 28 days grain or fodder; 7 days forage. REI 4 hr. Do not exceed 0.188 lb ai/a per season.
  • tebuconazole/lambda-cyhalothrin (Crossover) at 0.14 to 0.16 lb ai/a. PHI 21 days fodder and silage. REI 24 hr. Retreatment interval 7 days. Do not exceed 0.48 lb ai/a tebuconazole or 0.12 lb ai/a lambda-cyhalothrin per season.
  • zeta-cypermethrin (Mustang) at 0.04 to 0.05 lb ai/a. PHI 7 days for grain, stover and forage. Apply no more than 0.2 lb ai/a per season. Retreatment interval 3 days.

Kaur, N. (Ed.). 2023 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.