Pasture and grass hay-Armyworm and cutworm

Many species, including

Armyworm (Pseudaletia unipuncta)
Army cutworm (Chorizagrotis auxillaris)
Black cutworm (Agrotis ipsilon)
Glassy cutworm (Apamea devastator)
No common name (Protagrotis obscura)

Pest description and crop damage Larvae are 1 to 2 inches long at maturity. All, except glassy cutworm and Protagrotis obscura usually feed above ground on foliage after dark or during conditions of low light intensity. Larvae cause most damage to new seedlings, particularly if the previous crop was heavily infested and the larvae were not controlled.

Management-chemical control

  • Bacillus thuringiensis kurstaki (Xentari, Dipel) at 0.5 to 2 lb product/a. PHI 0 days. REI 4 hr. Armyworms only. Most effective on small caterpillars, but use highest recommended rate for fully developed ones. Multiple applications may be necessary for effective control. A spreader sticker may improve performance. Some formulations are OMRI-listed for organic use.
  • beta-cyfluthrin (Baythroid XL) at 0.013 to 0.022 lb ai/a. PHI 0 days for grazing or hay. REI 12 hr. Do not exceed 0.089 lb ai/a per season. Retreatment interval 5 days.
  • bifenthrin (Brigade WSB) at 0.033 to 0.1 lb ai/a. PHI 30 days for forage and hay. REI 12 hr. Retreatment interval 14 days. Do not exceed 0.2 lb ai/a per season.
  • carbaryl (Sevin 4F) at 1 to 1.5 lb ai/a. PHI 14 days. REI 12 hr. Limit 2 treatments per year. Retreatment interval 14 days. Do not exceed 3 lb ai/a per year. Armyworms only.
  • carbaryl (Sevin 5 Bait) at 1.5 lb ai/a. PHI 7 days for harvest or grazing. Limit 2 treatments per year. REI 12 hr. Retreatment interval 14 days.
  • chlorantraniliprole (Coragen) at 0.045 to 0.098 lb ai/a. PHI 0 days. REI 4 hr. Retreatment interval 7 days. Do not exceed 0.2 lb ai/a or 4 applications per season.
  • chlorantraniliprole/lambda-cyhalothrin (Besiege, Voliam Xpress) at 0.49 to 0.98 lb ai/a. PHI 0 days for grazing or cut for forage; 7 days for cut grass to be dried and harvested for hay. Retreatment interval 7 days. REI 12 hr. Do not exceed 0.09 lb ai/a lambda-cyhalothrin or 0.2 lb ai/a chlorantraniliprole.
  • cyfluthrin (Tombstone) at 0.025 to 0.044 lb ai/a. PHI 0 days. REI 12 hr. Retreatment interval 5 days. Do not exceed 0.176 lb ai/a per season.
  • diflubenzuron (Dimilin 2L) at 0.03 lb ai/a. PHI 1 day for cutting. REI 12 hr. Must be applied at first sign of hatch and before larvae reach 0.25 inch. Do not exceed 0.03 lb ai/a (0.5 oz ai/a) per cutting or 0.09 lb ai/a (1.5 oz ai/a) per year.
  • gamma-cyhalothrin (Declare) at 0.0075 to 0.015 lb ai/a. PHI 0 days for grazing or cut for forage; 7 days for cut grass to be dried and harvested. REI 24 hr. Do not exceed 0.045 lb ai/a per season.
  • lambda-cyhalothrin (Warrior II) at 0.015 to 0.03 lb ai/a. PHI 0 days for grazing and forage; 7 days to be dried for hay. REI 24 hr. Do not exceed 0.03 lb ai/a per cutting or 0.09 lb ai/a per season.
  • malathion (Drexel Malathion 5EC) at 1.25 ai/a. PHI 0 days. REI 12 hr. Armyworms only. Limit 2 treatments. Treatment interval 14 days.
  • methoxyfenozide (Intrepid 2F) at 0.06 to 0.12 lb ai/a. PHI 0 days for grazing, forage; 7 days hay. REI 4 hr. Do not apply more than 0.5 lb ai/a per year. Armyworms.
  • sodium borate (Prev-Am Ultra) at 50 fl oz/100 gal. PHI 1 day. REI 4 hr. Retreatment interval 7 days.
  • spinosad (Entrust SC) at 0.031 to 0.062 lb ai/a. PHI 3 days hay or fodder; 0 days pasture/forage. REI 4 hr. Armyworms only. Do not apply more than 3 times in any 21 day period or more than 6 times/season. Hazardous to honeybees for up to 3 hours post application. Limit 0.186 lb ai/a per season. OMRI-listed for organic use.
  • zeta-cypermethrin (Mustang) at 0.028 to 0.05 lb ai/a. PHI 0 days graze and hay; 7 days straw and screenings. REI 12 hr. Do not exceed 0.2 lb ai/a per season. Retreatment interval 7 days.