HPIPM:Armyworm FC
Author: Frank B. Peairs[1]
Identification (and life cycle/seasonal history)
Mature armyworm, Mythimna unipuncta (Haworth), larvae are 25 to 40 millimeters (1.0-1.6 inches) in length, smooth bodied, and dark gray to greenish black. They are characterized by five stripes, three on the back and two on the sides, running the length of the body. While the stripes on the back are variable in color, the stripes on the sides are pale orange with a white outline. The head is marked with a netlike pattern of black markings.
The armyworm is unable to survive our winters, and armyworm moths migrate into the region in early summer. They lay their eggs in rows or clusters on the lower leaves of various grass crops. Dense grassy vegetation is preferred for oviposition. Newly hatched larvae move with a looping (inch-worm) action. Larvae feed at night and on cloudy days, hiding under crop debris during sunny periods. One or more generations may occur per year.
Plant Response and Damage
Armyworm feeding is mostly limited to grasses, although this insect will feed on a number of other plants when starving. In Colorado, armyworm is mostly a pest of corn and spring grains. In corn, larvae may later enter the ear tip.
Management Approaches
Chemical Control
Armyworms migrate in to corn from grasses or onto corn within grassy cornfields. They are mostly a problem later in the season. They feed on the corn plant from the bottom leaves upward. If the infestation threatens to consume the lower third or more of the foliage before hard dent stage, chemical control may be justified. It is unknown if control can be expected with Bt corn hybrids.
Product list for Armyworm:
| Pesticide | Product/Acre (Fl oz. or oz. product) | Preharvest Interval, remarks |
|---|---|---|
| FastacR,1 | 3.2 - 3.8 | 30 days grain and stover, 60 days forage. 12 hr REI. Extremely Hazardous to Bees! No more than 11.4 fl oz per season. |
| Bacillus thuringiensis1,2 | See labels | 0 days. 4 hour REI. Use of a spreader-sticker is recommended. |
| Beauveria bassiana1,2 | See labels | 0 days. 4 hr REI. Potentially pathogenic to bees; avoid applying where bees are foraging or around hives. |
| beta-cyfluthrinR,1,2 | 1.6 - 2.8 | 21 days. 12 hour REI. See labels. Extremely Hazardous to Bees! |
| bifenthrinR,1,2 | See labels | 30 days. 12 hour REI. Use rates below 0.08 lb a.i./acre only if spider mites are NOT a concern. Extremely Hazardous to Bees! |
| bifenthrin + chlorpyrifosR,1,2 | See labels | 30 days. 24 hour REI. Maximum 50.5 fl oz product/season. See labels for additional restrictions for individual active ingredients. Extremely Hazardous to Bees! |
| HeroR,1 | 4.0 - 10.3 | 30 days to harvest grain or fodder. 60 days to forage. 12 hour REI. See labels for additional restrictions for individual active ingredients. Do not apply more than 0.4 lb ai/acre/crop. Extremely Hazardous to Bees! |
| carbaryl1,2 | See labels | 48 days grain and stover, 14 days silage. 24 hour REI. Extremely Hazardous to Bees! |
| chlorantraniliprole (several formulations)1 | 14-20 | 1 day silage, 14 days grain. 4 hour REI. No more than 0.2 lb AI/A/season. |
| chlorpyrifos 4ER,1,2 | see labels | 21 days. 24 hour REI. Not for use on popcorn. Extremely Hazardous to Bees! |
| chlorpyrifos + gamma cyhalothrinR,1,2 | see labels | 21 days. 14 days to graze. 24 hour REI. Extremely Hazardous to Bees! |
| Cobalt AdvancedR,1 | 11-26 | 21 days. 14 days to graze. 24 hour REI. See labels for additional restrictions for individual active ingredients. Extremely Hazardous to Bees! |
| Grandevo1 | 1-3 lbs | 0 days. 4 hour REI. May be repellent to bees. |
| cyfluthrinR,1,2 | See labels | 21 days. 12 hour REI. See labels. Extremely Hazardous to Bees! |
| deltamethrinR,2 | see labels | 21 days to harvest grain or fodder. 12 days to forage. 12 hour REI. Do not apply more than 0.095 lb ai/acre/crop. Extremely Hazardous to Bees! |
| esfenvalerateR,1,2 | See labels | 21 days. Apply as necessary to maintain control. Extremely Hazardous to Bees! |
| Belt1 | 2 - 3 | 28 days grain, 1 day forage and silage. 12 hour REI. No more than 12 fl oz product/season. |
| gamma cyhalothrinR,1,2 | See labels | 21 days. 24 hour REI. Do not apply more than 0.12 lb a.i./acre/season. Extremely Hazardous to Bees! |
| lambda cyhalothrinR,1,2 | See labels | 21 days. 24 hour REI. Do not apply more than 0.12 lb a.i./acre/season. Extremely Hazardous to Bees! |
| BesiegeR | 6 - 9 | 1 day for forage, 7 days for hay. 24 hr REI. Make applications when bees are not actively foraging by applying during early morning or evening hours. See labels for additional restrictions for individual active ingredients. Do not apply more than 31 fl oz product/season. |
| methoxyfenozide2 | See labels | 21 days. 4 hour REI. No more than 1.0 lb AI/A/season. See label for timing information and crop rotation restrictions. |
| methomylR,1,2 | see labels | 21 days to harvest grain or fodder. 3 days to forage. 48 hour REI. Do not apply more than 2.25 lb ai/acre/crop. Extremely Hazardous to Bees! |
| permethrinR,1,2 | See labels | 30 days grain or fodder. 0 days forage. 12 hour REI. Liquids are Extremely Hazardous to Bees! |
| Radiant SC1 | 3 - 6 | 28 days. 3 days forage or fodder. 4 hour REI. Toxic to bees for 3 hours after application. |
| spinosad1,2 | 1 - 3 | 28 days grain, 3 days fodder or forage. 4 hour REI. Toxic to bees for 3 hours after application. |
| ConseroR,1 | 2-3 | PHI 28 days, 1 day graze or fodder; REI 24 hrs. See labels for additional restrictions for individual active ingredients. |
| Mustang MaxxR,1 | 3.2 - 4.0 | 7 days. 12 hour REI. Extremely Hazardous to Bees! No more than 0.10 lb AI/A/season. |
| StallionR,1 | 9.25 - 11.75 | 30 days grain or stover, 60 days forage. 24 hr REI. Extremely Hazardous to Bees! See labels for additional restrictions for individual active ingredients. No more than 11.75 oz per application, 35.25 oz per season. |
| SteedR,1 | 3.5-4.7 | PHI 30 days grain, 60 days forage; REI 12 hrs. See labels for additional restrictions for individual active ingredients. No more than 18.7 fl oz product/season. |
| Triple CrownR,1 | 4.5 - 10.3 | PHI 30 days grain, 60 days forage; REI 12 hrs. See labels for additional restrictions for individual active ingredients. No more than 30.7 fl oz product/season. |
| RRestricted use pesticide. 1Labeled for chemigation. 2Generic active ingredient, several formulations. | ||
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
