Corn, sweet-Armyworm

Includes

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

Pest description, crop damage and life history

See:

Common Pests of Vegetable Crops

Pest Monitoring The bertha armyworm is considered a "climbing cutworm" because it spends little time near the ground. It can be easy to miss while scouting, because though eggs and young instars tend to be clustered, later in the year they disperse actively. Larvae also drop quickly from plants when disturbed, avoiding detection. During outbreak years, populations can explode due to an influx of overlapping generations of migrating moths along with overwintering populations.

Pheromone traps are useful for determining when major flights occur, but not for predicting damage. There is currently no satisfactory, commercially available pheromone for bertha armyworm. If any moths are detected in pheromone traps, take a close look at the field during the following 2 weeks as eggs hatch and colonies of armyworm develop. A 5-minute timed search helps determine the need for treatment. On average, if one or more larvae or egg masses are found in 5 minutes, treatments may be justified.

In those rare instances when control measures are required, the beet armyworm is more difficult to control than the western yellowstriped armyworm. Insecticide applications are most effective if applied against small larvae.

Management-biological control

Common natural enemies of armyworms include several braconid and ichneumonid wasps, many general predators including assassin bugs, damsel bugs, and spiders, and a nuclear polyhedrosis virus reported to have brought about excellent late year control in Canada. None of these natural enemies can be counted upon to achieve adequate control in any given year.

Management-cultural control

Weed control is important. Lambsquarters and wild mustard attract egg-laying females and provide a source of food for larvae. Fall tillage can help destroy overwintering pupae.

Management-chemical control: HOME USE

Armyworms are easier to control when small. Thus, it is good practice to keep close watch on plants and apply control measures against the immature larvae.

• azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
• Bacillus thuringiensis var. kurstaki (Btk)-Some formulations are OMRI-listed for organic use.
• bifenthrin (often as a mix with zeta-cypermethrin).
• carbaryl
• cyfluthrin
• deltamethrin
• esfenvalerate
• gamma-cyhalothrin
• horticultural oil-Some formulations are OMRI-listed for organic use.
• insecticidal soap (as a mix with spinosad) -Some formulations are OMRI-listed for organic use.
• kaolin-Applied as a spray to leaves, stems, and fruit, it acts as a repellant to some insect pests. Some formulations are OMRI-listed for organic use. Not registered for use in OR.
• lambda-cyhalothrin
• permethrin
• plant derived essential oils (rosemary, peppermint, etc.)-Some formulations are OMRI-listed for organic use.
• pyrethrins-Some formulations are OMRI-listed for organic use.
• spinosad-Some formulations are OMRI-listed for organic use.
• zeta-cypermethrin

Management-chemical control: COMMERCIAL USE

Armyworms are easier to control when small. Thus, it is good practice to use pheromone traps to anticipate egg deposition and hatch, and to keep close watch on fields and apply control measures against the immature larvae.

• azadirachtin-See label for application rates. Some formulations are OMRI-listed for organic use.
• alpha-cypermethrin (Fastac EC) at 0.018 to 0.025 lb ai/A. PHI 3 days. REI 12 hr. Retreatment interval 3 days. Do not exceed 0.075 lb ai/A per season.
• Bacillus thuringiensis (Javelin WG) 0.12 to 1.5 lb/A. PHI 0 days. REI 4 hr. Armyworms only. Use a spreader-sticker to enhance control. Some formulations are OMRI-listed for organic use.
• bifenthrin (Capture LFR) at 0.04 to 0.16 lb ai/A at planting; 0.047 to 0.062 lb ai/A pre-plant incorporated; 0.04 lb ai/A pre-emergence; 0.033 to 0.1 foliar. PHI 1 day for foliar. REI 12 hr. Do not exceed 0.2 lb ai/A per season.
• bifenthrin/IBA (Empower 2) at 0.04 to 0.1 lb ai/A. PHI 1 days. REI 24 hr (Varies based on crop use; refer to label). Do not exceed 0.2 lb ai/A per year. Product not registered for use in WA.
• bifenthrin/zeta-cypermethrin (Hero) at 0.04 to 0.1 lb ai/A. PHI 3 days. REI 12 hr. Retreatment interval 3 to 5 days. Do not exceed 0.266 lb ai/A per season.
• beta-cyfluthrin (Baythroid XL) at 0.013 to 0.022 lb ai/A. PHI 0 days. REI 12 hr. Retreatment interval 2 days. Do not exceed a total of 0.22 lb ai/A per growing season.
• borate complex (Prev-Am) applied as a 0.8% solution. Apply to complete coverage. REI 24 hr. Retreatment interval 7 days. OMRI-listed for organic use.
• Burkholderia spp. (Venerate XC) at 1 to 4 quarts/A product. PHI 0 days. REI 4 hr. OMRI-listed for organic use.
• carbaryl (Sevin XLR Plus) at 1 to 2 lb ai/A. PHI 2 days for harvest of ears, 14 days for forage, or 48 days for fodder. REI 24 hr. Do not exceed 16 lb ai/A per year. Retreatment interval 3 days. Limit 8 treatments per year.
• chlorantraniliprole (Coragen) at 0.045 to 0.098 lb ai/A. PHI 1 day. REI 4 hr. Limit 4 treatments per crop. Retreatment interval 1 day. Do not exceed 0.2 lb ai/A per season.
• chlorantraniliprole/lambda-cyhalothrin (Besiege) at 0.059 to 0.98 lb ai/A. PHI 1 day. REI 24 hr. Retreatment interval 1 day. Do not exceed 0.48 lb ai of lambda-cyhalothrin or 0.2 lb ai of chlorantraniliprole per acre per growing season.
• 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 production.
• deltamethrin (Delta Gold) at 0.018 to 0.028 lb ai/A. PHI 1 day. REI 12 hr. Do not exceed 0.45 lb ai/A per year.
• esfenvalerate (Asana XL) at 0.03 to 0.05 lb ai/A. PHI 1 day. REI 12 hr. Do not exceed 0.5 lb ai/A per year.
• gamma-cyhalothrin (Declare) at 0.01 to 0.015 lb/A. REI 24 hr. PHI 1 day. Do not graze. Do not exceed 0.24 lb ai/A per season.
• lambda-cyhalothrin (Warrior II) at 0.02 to 0.03 lb ai/A. PHI 1 day. REI 24 hr. Do not exceed 0.48 lb ai/A per year. Retreatment interval 4 days. Do not harvest for feed or graze livestock for 21 days.
• lambda-cyhalothrin/tebuconazole (Crossover) at 0.14 to 0.16 lb ai/A. REI 19 days. PHI 21 days for ears & forage; 49 days for fodder. Do not exceed 0.48 lb ai/A tebuconazole or 0.12 lb ai/A lambda-cyhalothrin. Product not registered for use in WA.
• malathion (Malathion 5EC) at 1.0 lb ai/A. PHI 5 days. REI 12 hr, dependent on activity; refer to label for REI. Retreatment interval 5 days. Limit 2 treatments per year.
• methomyl (Lannate SP) at 0.23 to 0.45 lb ai/A. PHI 0 days for ears, 3 days for forage, and 21 days for stover. REI 48 hr. Do not exceed 6.3 lb ai/A per season.
• methoxyfenozide (Troubadour 2F) at 0.06 to 0.25 lb ai/A. PHI 3 days for ears or forage, and 21 days for dry fodder. REI 4 hr. Do not exceed 1 lb ai/A per season. An adjuvant will improve performance. Retreatment interval 5 days.
• novaluron (Rimon 0.83 EC) at 0.039 to 0.078 lb ai/A. PHI 1 day. REI 12 hr. Retreatment interval 7 days. Do not exceed 0.39 lb ai/A per season.
• permethrin (Permethrin Cutworm Bait) at 0.1 to 0.2 lb ai/A. PHI 1 day. REI 12 hr. Retreatment interval 3 days. Do not exceed 0.45 lb ai/A per year.
• spinetoram (Radiant SC) at 0.023 to 0.0469 lb ai/A. PHI 1 day for ears, 3 days for forage. REI 4 hr. Retreatment interval 2 days. Do not exceed six applications or 0.281 lb ai/A per season. Follow resistance management procedures on the label.
• spinosad (Success, Entrust SC) at 0.023 to 0.094 lb ai/A. PHI 1 day for ears, and 7 days for forage. REI 4 hr. Do not exceed 0.45 lb ai/A per year. Entrust SC is OMRI-listed for organic use.
• zeta-cypermethrin (Mustang) at 0.04 to 0.05 lb ai/A. PHI 7 days for grain, stover & forage. REI 12 hr. Do not exceed 0.2 lb ai/A per season.