ARMYWORMS: Noctuidae

ADULT: These moths have light to medium brown front wings and body.  Hind wings are lighter colored, sometimes with a dark band around margins. Light and dark wing markings may not be present on older moths.

EGG: The moths produce egg masses of up to 200 eggs covered with scales, generally found underneath leaves or on husks or silks.

LARVA: Full grown caterpillars may reach 2 in. and range in color from light green to nearly black. Spodoptera spp. larvae have definite teeth on their mandibles.  Sutures on front of head form an inverted "Y".  Larvae have three pairs of true legs and five pairs of prolegs. They feed on leaves, silks, husks and ears for approximately 2 wk. and pass through up to six instars.

PUPA: Larvae burrow into the soil near the base of plants to complete metamorphosis. Adults emerge in 7 to 10 d.

DAMAGE: Larvae can cause severe damage to leaves and stalks resulting in plant death, stunting, or lack of tassel production. Older plants can withstand considerable leaf and tassel feeding.  However, allowing larvae to complete development as tassels emerge usually leads to early, devastating ear damage.  Tip damage to ears can be trimmed, but other damage results in an unmarketable product. Young larvae often enter ear through silk canal or tips of husks. Older larvae can enter the ear through husk or shank.

HOSTS: Armyworm larvae feed on a wide range of cultivated and uncultivated plants.

CONTROL: Birds and insect natural enemies aid in armyworm control, but generally do not exert enough pressure to prevent yield loss, particularly in sweet corn. Host plant resistance is emerging as an effective control strategy against armyworms in both field and sweet corns. Varieties with insect enzyme inhibitors and new bioengineered corns with bacterial toxins will help to greatly reduce armyworm feeding pressure. Pesticidal controls are most effective against the younger instars with higher rates and more frequent applications needed to control later instars. Granular formulations of several pesticides are available that reduce the exposure to non-target organisms by concentrating the pesticides in the whorls and leaf axils, particularly when applied in tight bands over the rows. The other pesticides are used as broadcast or banded sprays. Fields should be monitored for young larvae on leaves and in whorls at least weekly until tassel push. Thresholds used for treatment are plant age specific, with seedlings and plants pushing tassel often treated at 10% or lower infestations. Plants between these stages are usually treated when infestations reach between 15 and 20%. Research has shown the importance of reducing armyworm populations as low as possible in the period leading up to and during tassel push. Sweet corn produces copious amounts of pollen that can compensate for damaged tassels. But it is important to eliminate the larvae being pushed from the whorl by the emerging tassel so they do not damage the sensitive emerging ears and do not pupate within the field. Armyworms completing development at tassel push will emerge as adults to lay eggs on the crop during the period of active silk growth. Fields should be scouted at least twice weekly during the ear stage to detect and control populations before they cause economic damage. Thresholds used during this period range between 2 and 8%, with estimates at the high end eliciting more frequent sampling. Formulations, rates, and pre-harvest intervals of insecticides labeled for armyworm control in Florida are listed below for sweet corn (Table 1) and field corn (Table 2).

Table 1.  Chemical control of armyworms in sweet corn
Insecticide, formulation Rate/acre Min. days to harvest Application notes
Bacillus thuringiensis    
carbaryl (Sevin, Sevin XLR Plus) 4 F, 4 EC 1 - 2 qt 2 ears; 48 forage; 14** AW, FAW
carbaryl (Sevin) 80 WSP 1.25 - 2.5 lb 2 ears; 48 fodder; 14** AW, FAW
carbofuran (Furadan) 4 F 2.5 fl oz / 1000 row-ft 30 feed forage FAW; aids in control; at plant in-furrow
chlorpyrifos (Lorsban) 4 E *** 1 - 2 pt 35 fodder, grain; 14 grazing, silage AW; Federal label
chlorpyrifos (Lorsban) 4 E *** 1 - 2 pt 7 ears; no grazing, feeding of silage, forage or fodder to meat or dairy animals FAW, BAW; State label
chlorpyrifos (Lorsban) 15 G 6 - 8 oz / 1000 row-ft 35 grain, fodder; 14 ** AW; banded
cyfluthrin (Baythroid 2) 2 EC 2.8 fl oz 0 FAW
cyhalothrin (Karate, Warrior) 1 EC 2.56 - 3.84 fl oz 1 BAW, FAW, SAW
esfenvalerate (Asana XL) 0.66 EC 5.8 - 9.6 fl oz 1 AW,  BAW
ethyl parathion (Parathion) 8 EC 0.75 pt 12 FAW
methomyl (Lannate LV) 2.4 EC 0.75 - 1.5 pt 0 ears; 3 forage AW, BAW, FAW
methomyl (Lannate SP) 90 WSP 0.25 - 0.5 lb 0 ears; 3 forage AW, FAW; BAW
methomyl 5 G 3 lb 3 forage, grazing FAW; banded by ground only
methoxychlor 2 EC 2 - 4.5 qt 7 ears; do not feed to livestock AW, FAW; ground app. only
oil (Ultra Fine Sun Spray) 7 E 1 - 2 gal/100 gal water   FAW
permethrin (Ambush) 2 EC 6.4 - 16.0 fl oz 1 FAW, SAW
permethrin (Ambush) 25 WP 6.4 - 16.0 oz 1 FAW, SAW
permethrin (Pounce) 1.5 G *** 6.7 - 13.3 lb 1 AW; broadcast or banded
permethrin (Pounce) 25 WP 6.4 - 12.8 oz 1 FAW, SAW
permethrin (Pounce) 3.2 EC 4 - 8 fl oz 1 FAW, SAW
thiodicarb (Larvin) 3.2 EC 20 - 30 fl oz 0 ears; do not feed to livestock AW
AW = armyworm, BAW = beet armyworm, FAW = fall armyworm, SAW = southern armyworm, TAW = true armyworm
**harvest or grazing of forage or silage
***check label for other application techniques and rates


Table 2.  Chemical control of armyworms in field corn
Insecticide, formulation Rate/acre Min. days to harvest Application notes
Bacillus thuringiensis See various brand labels ---
carbaryl (Sevin, Sevin XLR Plus) 4 F, 4 EC 1 - 2 qt 48 fodder, grain; 14** AW, FAW
carbaryl (Sevin) 80 WSP 1.25 - 2.5 lb 48 fodder, grain; 14** AW, FAW
carbofuran (Furadan) 4 F 2.5 fl oz / 1000 row - ft 30 feed forage FAW; aids in control; at planting in furrow
chlorpyrifos (Lorsban) 4 E *** 1 - 2 pt 35 fodder, grain; 14 grazing, silage AW
chlorpyrifos (Lorsban) 15 G 6 - 8 oz / 1000 row - ft 35 grain, fodder; 14 ** AW; banded
cyhalothrin (Karate, Warrior) 1 EC 2.56 - 3.84 fl oz 21 AW, FAW
esfenvalerate (Asana XL) 0.66 EC 5.8 - 9.6 fl oz 21 TAW
ethyl parathion (Parathion) 8 EC 0.75 pt 12 AW, FAW
malathion (Malathion) 5 EC 2 pt 7  
methomyl 5 G 3 lb 3 grazing or feed plants FAW; banded by ground only
methomyl (Lannate LV ) 2.4 EC 0.75 - 1.5 pt 3 forage; 21 ear, fodder AW, BAW, FAW
methomyl (Lannate SP) 90 WSP 0.25 - 0.5 lb 3 forage; 21 ear, fodder AW, BAW, FAW
methoxychlor 2 EC 2 - 4.5 qt 7 ears; do not feed to livestock AW, FAW
methyl parathion (Penncap - M) 2EC 2 - 3 pt 12 TAW
oil (Sun Spray) 7 E 2 gal/100 gal water   FAW; early spring, summer
permethrin (Ambush) 2 EC 6.4 - 12.8 fl oz 30 harvest of fodder, grain AW, pre- and post- emerge
permethrin (Ambush) 25 W 6.4 - 12.8 oz 30 harvest of fodder, grain AW, pre- and post- emerge
permethrin (Pounce) 1.5 G 6.7 - 13.3 lb / ac or 8 - 16 oz / 1000 row-ft 30 harvest of fodder, grain AW; broadcast or banded at plant or post-emerge
permethrin (Pounce) 25 WP 6.4 - 12.8 oz or 0.5 - 1.0 oz / 1000 row-ft 30 harvest of fodder, grain AW, FAW; broadcast or banded pre-emerge, at plant, or post-emerge
permethrin (Pounce) 3.2 EC 4 - 8 fl oz or 0.3 - 0.6 fl oz / 1000 row-ft 30 harvest of fodder, grain AW, FAW; broadcast or banded pre-emerge, at plant, or post-emerge
permethrin (Pounce WSB) 24.7% WSB 6.4 - 12.8 oz 30 harvest of fodder, grain AW; broadcast  pre- or post-emerge
AW = armyworm, BAW = beet armyworm, FAW = fall armyworm, TAW = true armyworm
**harvest or grazing of forage or silage
***check label for other application techniques and rates