1. Insect
  2. Legume, Grass, and Field Seed Crops
  3. Pests of Alfalfa Grown for Seed

Alfalfa seed-Armyworm

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Image related to Alfalfa seed-Armyworm
Western yellowstriped armyworm
Spodoptera praefica Grote
Egg(s) on host
© Ken Gray Insect Image Collection
Image related to Alfalfa seed-Armyworm
Western yellowstriped armyworm
Spodoptera praefica Grote
Adult
© Ken Gray Insect Image Collection
Image related to Alfalfa seed-Armyworm
Western yellowstriped armyworm
Spodoptera praefica Grote
Young immature showing damage on leaves
© Ken Gray Insect Image Collection

Includes

Bertha armyworm (Mamestra configurata)
Western yellowstriped armyworm (Spodoptera praefica)

Pest description and crop damage Caterpillars are 1.5 to 2 inches long when mature. Color varies within a species and within larvae in a field. They may be velvety black-with two prominent and several fine, bright yellow stripes on the sides-to plain green. Both species may be found on foliage during the day as well as night.

Management-chemical control

  • Bacillus thuringiensis kurstaki (Deliver) at 0.25 to 1.5 lb product/A. PHI 0 days. REI 4 hr. Most effective on small caterpillars; use highest recommended rate for fully developed ones. A spreader-sticker may improve performance.
  • chlorantraniliprole (Coragen) at 0.045 to 0.098 lb ai/A. PHI 0 days. REI 4 hr. Make no more than 4 applications per acre per crop. Do not make more than one application per cutting. Do not apply more than 15.4 fl oz Coragen or 0.2 lb ai of chlorantraniliprole per acre per crop.
  • chlorantraniliprole/lambda-cyhalothrin (Voliam Xpress) at 5 to 8 fl oz/A. PHI 1 day for forage and 7 days for hay. REI 24 hr. Minimum of 5 days between applications. Do not exceed a total of 31.0 fl oz of Voliam Xpress or 0.12 lb ai of lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole per acre per growing season.
  • gamma-cyhalothrin (Proaxis, Declare) at 0.01 to 0.015 lb ai/A. PHI 1 day for forage, 7 days for hay. REI 24 hr. Do not exceed 0.06 lb ai/A per cutting or 0.015 lb ai/A per cutting. Do not apply on ground within 25 ft of aquatic habitat, 150 ft if applied by air, or 450 ft if applied from ULV.
  • lambda-cyhalothrin (Warrior) at 0.02 to 0.03 lb ai/A. PHI 1 day for forage, 7 days for hay. REI 24 hr. Do not exceed 0.03 lb ai/A per cutting or 0.12 lb ai/A per season. Do not apply on ground within 25 ft of aquatic habitat, 150 ft if applied by air, or 450 ft if applied from ULV. Do not apply while bees are active. Advisable to move bee shelters for 2 to 3 days after application.
  • malathion 8EC at 1.0 to 1.25 lb ai/A. PHI 0 days. REI 12 hr. Not effective below 65ºF. Not recommended for fields pollinated with leafcutting bees. WA only.
  • permethrin at 0.05 to 0.2 lb ai/A. PHI 0 days at rates equal to or less than 0.1 lb ai/A, 14 days at rates greater than 0.1 lb ai/A. REI 12 hr. Do not reapply at less than 7-day intervals or exceed 0.2 lb ai/A per cutting. If used during bloom, remove bees from field for 3 days.
  • zeta-cypermethrin (Mustang) at 0.035 to 0.05 lb ai/A. PHI 3 days for cutting or grazing, 7 days for harvest. REI 12 hr. Do not reapply at less than 7-day intervals or exceed 0.1 lb ai/A per cutting or 0.3 lb ai/A per season. Do not apply on ground within 25 ft of aquatic habitat, 150 ft if applied by air, or 450 ft if applied from ULV.