FALL ARMYWORM: Spodoptera frugiperda, Noctuidae

ADULT: Light brown to ash gray moth with 1 1/2 in. wing span. Several dark and light spots and lines are found on fore wings. The hind wings are lighter with a dark band near the margin. Adults are larger than beet armyworm adults.

EGG: They are deposited in masses of up to 200 eggs, often with more than one layer, and covered with scales from the moth's abdomen. Egg masses are usually deposited under leaves on the lower 1/3 of the plant. Larvae emerge in 3 to 4 d.

LARVA: Newly emerged larvae are all white with black heads. Body color darkens as they grow. Mature larvae grow to about 2 in. and are light green to tan to brown or nearly black. Larvae have six dark bumps (tubercles) greater than or equal to the size of their spiracles on each abdominal segment. The eighth abdominal segment has four distinct dark bumps on the top surface. The top of the first thoracic segment appears as a dark shield, often with three light stripes.  Sutures on front of head form an inverted "Y". Larvae have three pairs of true legs and five pairs of prolegs.

PUPA: The dark reddish-brown 3/4 in. pupae are found in soil. Adults emerge in 7 to 10 d.

GENERATION TIME: 25 to 30 d.

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

DAMAGE: Young larvae feed between leaf veins often on outer portions of leaves before moving into the whorl to feed on young leaves. Leaves damaged within the whorl often emerge to display rows of holes. Larger larvae can completely consume the growing point of the plant, or can severely damage the tassel before it emerges from the whorl. Fourth through sixth instar larvae pushed from the whorl by the emerging tassel can quickly ruin the ears of at least one of the surrounding plants. All age larvae feed on ears. Young larvae feed on silk and often enter tip of ear to feed on silk, kernels and cob. Older larvae can enter the ear through the husk.

CONTROL: Birds and insect natural enemies (predators and parasitoids) aid in fall armyworm (FAW) 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 FAW in both field and sweet corns. Varieties with insect enzyme inhibitors and new bioengineered corns with bacterial toxins will help to greatly reduce FAW feeding pressure. Pesticidal controls are most effective against the younger instars with higher rates and more frequent applications needed to try 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 at least weekly until tassel push for young larvae on leaves and in whorls. 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 FAW 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. FAW 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 FAW control in Florida are listed below for sweet corn (Table 1) and field corn (Table 2).