1. Insect
  2. Agronomic Crops
  3. Field and Silage Corn Pests

Field and silage corn-Armyworm

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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 Armyworm are similar in appearance to beet armyworm adults, both light gold-brown with white underwings. However, armyworms have a small white dot on the forewing. Larvae of beet armyworm are bright to olive green, while armyworm larvae will have brownish-black stripes along the upper sides of the body. Outbreaks are cyclic, occurring every 7 to 12 years, and may last up to three years. Feeding damage from larvae occurs from August through October and is usually more severe in cooler, wet conditions. Mature larvae are 1.5 inches in length. Color varies from brown (armyworm) to green. Egg masses are pale green to pink and will be found in masses covered with cotton-like filaments. Moths are attracted to barnyard grass; therefore, it is important to control these weeds in corn fields.

Management-biological control

Tachinid flies are valuable biological organisms that deposit eggs that parasitize armyworm larvae.

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 and Fastac EC) 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. IRAC Group 3A.
  • azadirachtin (Aza-Direct, Azaguard and several formulations) at 0.02 to 0.35 lb ai/A. PHI 0 days. REI 4 hr. Some formulations are OMRI-listed for organic use. Biological insecticide/nematicide.
  • Bacillus amyloliquefaciens D747 TGAI/bifenthrin (Ethos 3D, Ethos XB) at 0.04 to 0.2 lb bifenthrin ai/A. Do not exceed 0.3 lb bifenthrin on field corn per season. REI 12 hr. IRAC Group 3A insecticide, Group 44 fungicide.
  • Bacillus thuringiensis (Javelin WG) biological insecticide at 0.5 to 1.5 lb/A. PHI 0 days. Use according to individual manufacturer's label instructions. OMRI-listed for organic use. Tested on corn silage in the Coos Bay area and found effective only on very young larvae.
  • beta cyfluthrin (Baythroid XL) at 0.013 to 0.022 lb ai/A (1.6 to 2.8 fl oz/A). PHI 0 days for green forage, and 21 days for grain or fodder. REI 12 hr. Do not exceed four applications or 0.175 lb ai/A per season. IRAC Group 3.
  • bifenthrin Group 3A insecticide/miticide -
  • Brigade 2EC 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.
  • Sniper LFR at 0.04 to 0.16 lb ai/A. Apply as T band over open furrow or in-furrow with seed. Do not apply more than 0.2 lb ai/A at plant. Field corn-Do not exceed 0.3 lb bifenthrin/A/season including pre-plant.
  • Capture LFR at 0.04 to 0.2 lb ai/A (3.4 to 17.0 fl oz/A).
  • bifenthrin/chlorantraniliprole (Elevest and others) at 0.098 to 0.167 lb ai/A. REI 12 hr. PHI 30 days. No more than three applications per year. Do not apply more than a total of 0.2 lb ai/A of chlorantraniliprole and 0.3 lb ai/A of bifenthrin per year. IRAC Group 3A and 28.
  • bifenthrin/zeta-cypermethrin (Hero EW) at 0.04 to 0.1 lb ai/A foliar or at planting (4.5 to 11.2 fl oz/A). See label for row spacing or per linear feet. PHI 30 days grain and stover; 60 days forage. REI 12 hr. Do not graze for 30 days after treatment. Do not exceed 0.1 lb ai/A at-plant application, or 0.099 lb/A zeta-cypermethrin and 0.398 lb/A bifenthrin per year. IRAC Group 3A.
  • Burkholderia spp. (Venerate XC) bioinsecticide at 1 to 4 quarts/A. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.052 to 0.08 lb ai/A (6.0 to 10.0 fl oz/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. Use higher listed rates within listed range for large larvae. IRAC Group 3 & 28.
  • 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. IRAC Group 28.
  • Chromobacterium subtsugae (Grandevo) bioinsecticide at 0.3 to 0.9 lb ai/A per 100 gal (1.0 to 3.0 lb product /A). PHI 0 days. REI 4 hr. OMRI-listed for organic use.
  • cyfluthrin (Tombstone)-Apply to 1st and 2nd instar only at 0.025 to 0.044 lb ai/A (1.6 to 2.8 fl oz/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. IRAC group 3A.
  • deltamethrin (Delta Gold) at 0.018 to 0.022 lb ai/A (1.5 to 1.9 fl oz/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. IRAC Group 3.
  • esfenvalerate (Asana XL) at 0.03 to 0.05 lb ai/A (5.8 to 9.6 fl oz/A). PHI 21 days. REI 12 hr. Do not exceed 0.25 lb ai/A per season. IRAC Group 3.
  • 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. IRAC Group 3 insecticide.
  • 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. IRAC Group 22 insecticide.
  • 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. IRAC Group 3 insecticide.
  • malathion (Drexel Malathion 5EC) at 0.6 to 1 lb ai/A (1 pint/A). Limit 2 treatments per year. Retreatment interval 7 days. PHI 7 days. REI 72 hr for detasseling, 12 hr for other activities. IRAC Group 1 insecticide.
  • 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. Restricted use pesticide. IRAC Group 1A.
  • 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. IRAC Group 18.
  • 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. IRAC group 5 & 18.
  • permethrin (Several available) - See label for specific application rates. Tested in the Coos Bay area and found not effective for controlling armyworm in Silage corn. Group 3 insecticides
  • spinetoram (Radiant SC) Group 5 insecticide 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, Entrust SC) 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. Some organic formulations. IRAC group 5.
  • tebuconazole/lambda-cyhalothrin (Crossover) Group 3 fungicide/insecticide 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, Mustang MAXX) at 0.02 to 0.025 lb ai/A Mustang MAXX, 0.04 to 0.05 lb ai/A Mustang. REI 12 hr. PHI 7 days for field corn. Apply no more than 0.02 Mustang, and 0.1 lb ai/A MAXX per season. Group 3A.