NPIPM:Pseudoplusia includens (soybean)
Authors: Buyung Hadi and Jeffrey Bradshaw
Soybean looper, Pseudoplusia includens, is a member of a moth family common in North, South and Central America. Pseudoplusia includens is not the only looper that maybe found on soybean. Other species such as cabbage looper, Trichoplusia ni, may form a species complex of loopers feeding on soybean. Nevertheless soybean looper usually dominate the looper complex.
Identification
The larva is the only part of soybean looper life cycle that is injurious to soybean. The soybean looper larva is green in color with light colored stripes on both sides of the body and along the back. A fully developed soybean looper larva is about 1.3 in (35 mm) long. Soybean looper has two pairs of abdominal prolegs, on segments 5 and 6, and a pair of anal prolegs. Green cloverworm, which looks superficially similar to soybean looper, has three pairs of abdominal prolegs and a pair of anal prolegs. The arrangement of the abdominal legs cause the larva of soybean looper to hump its back when moving, earning the common name 'looper'. The forewings of the adult moth of soybean looper are mottled brown with a bronze to golden glitter. At the center of the forewings, two prominent silver markings are usually visible.
Life Cycle and Seasonal History
Soybean looper is only known to overwinter in the southernmost states. Its occurence in northern plains is rather uncommon. Adult moths are transported by the weather system to the northern states in the spring and summer.
Mated female moths lay eggs on the underside of soybean leaves. The eggs take three days to hatch and the resulting larvae feed on soybean leaves. During the next two weeks, the larvae go through through six developmental stages (instars) and begin to pupate. The pupae are covered by silken cocoons attached on the underside of soybean leaves. In about another week, adult moths emerge from the pupae. Only one generation is produced in the northern states.
Plant Injury and Damage
The larvae feed on soybean leaves. The first two instars feed on the underside of the leaf and are unable to feed on the leaf's upper cuticle, leaving a transparent appearance on parts of the leaf. Later instars feed on leaf tissues and, avoiding large lateral veins, produce irregular holes on the leaves.
Generally, soybean loopers' feeding activity does not induce economic damage on soybean, especially in the northern states. In the Gulf coast and Southeastern Atlantic coast states, outbreak populations may occur.
Management Approaches
Scouting and Threshold
Since soybean loopers alone do not typically cause economic damage,defoliation due to soybean looper feeding should be considered together with the damage inflicted by other defoliating caterpillars in making a management decision. Treatment is recommended if defoliation reaches 40% pre-bloom, 20% during bloom and pod-fill, or 35% from pod-fill to harvest.
Other Online Resources
For information regarding labels of chemical control options, please visit Agrian.com
