Southern Armyworm (Spodoptera eridania)

southern army worm

southern army worms

southern army worms
Images courtesy of Dr. Ron Smith:
Auburn University and University of
Georgia IPM image website
(http://www.ipmimages.org)
Introduction

The southern armyworm is native to tropical areas in North, South and Central America. In the United States, it is most commonly found in the southeastern states. However, it has been reported as for north as Kansas and as far south as New Mexico and California. In some states, it appears to be increasing in importance as a pest.

Identification
Southern armyworm larvae may be green, gray or black in appearance with lighter colored stripes. There are triangular markings on each body segment with the exception of the first thoracic segment. Unlike the fall armyworm, the southern armyworm does not have an inverted Y on its head capsule.

Adult southern armyworms have forewings that are gray or brown with irregular markings. The hindwings are white. The moths have a wingspan of between 33 to 38 mm (about 1 to 1½ inches).

Eggs of the southern armyworm, like other armyworms, are laid in clusters and covered with scales and hair from the female.

Biology
The biology of the southern armyworm is not well documented. In warmer climates, such as that found in Florida or Georgia, four or five generations may occur. Females lay egg masses that are similar in appearance to those of beet armyworm and fall armyworm, but tend to be larger. Larvae are usually found on the lower leaf surfaces and tend to be more active at night. The larval stage may last between 14 and 20 days dependent on temperature. Pupation occurs in the soil and new adults will emerge in 11 to 13 days. A complete life cycle takes between 30 and 40 days.

Damage
Southern armyworm larvae are usually found on the lower leaf surfaces and tend to be more active at night. Larvae feed gregariously while young, often skeletonizing leaves. Very high infestations may occur in localized spots in a field. Defoliation of plants may occur. As they mature they become solitary, and may also bore readily into the boll.

Control
Control with conventional insecticides is based on a defoliation threshold and is generally effective. Treatable levels of infestation occur in Florida and Georgia more often than in other cotton producing states. In Georgia, incidents of outbreaks seem to be increasing. WideStrike™ Insect Protection has been shown to be very effective against southern armyworm.