SOUTHERN ARMYWORM: Spodoptera eridania, Noctuidae

ADULT: Fore wings with 1 1/2 in. wing span are streaked with cream, gray, light brown, and black, and an elongate white mark across the rear outer corner. A dark kidney-shaped spot (reniform spot) is present near the middle of the fore wings. Hind wings are white with a few dark marks on the margins.

EGG: They are produced in masses of 100 to 200 eggs and covered with scales from the female's abdomen. Eggs are usually deposited on the underside of leaves. Larvae emerge in 3 to 4 d.

LARVA: These caterpillars are often very colorful and grow to 2 in. long at maturity. Head color is light to reddish-brown. Their bodies have a narrow, almost continuous white to orange stripe down the center of the back. A yellowish to orange broad band runs backward from the first abdominal segment below the spiracles. Some to all abdominal and some thoracic segments have dark triangular markings near the center of the back. Darker specimens exist where bands and markings are very faint. Each thoracic segment and first two abdominal segments are larger than previous segment giving a distinctive swollen or hump-backed appearance to larvae, particularly in late instars.  Sutures on front of head form an inverted "Y". Larvae have three pairs of true legs and five pairs of prolegs.  Larval development is completed in 14 to 21 d.

PUPA: Brown pupae are found in the soil. Adults emerge in 7 to 8 d.

GENERATION TIME: 24 to 33 d.

DAMAGE: Southern armyworm is an occasional pest of young corn and corn ears. Feeding damage is similar to that of the fall armyworm.

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 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 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 southern armyworm control in Florida are listed below for sweet corn (Table 1) and field corn (Table 2).