Insect Management
Cotton Insect Management
Cabbage Looper -
Trichoplusia ni (Hubner)
Description
The egg, larva, pupa, and adult are the four stages of development of the
cabbage looper. The small white egg is laid by the adult on the upper and lower
surface of leaves. The eggs are greenish - white. They are flattened on the side
attached to the plant and this characteristic helps distinguish them from
bollworm eggs.
The larva is a light green worm with several white lines down the length of
the body. The larvae arches or loops their body as they crawl - thus the name
cabbage looper. Three pair of prolegs occur at the rear of the body. The full
grown larva is about 1-1 / 2 inches long. They are found mainly on foliage. The
pupa is initially a light green turning to a brown color and enclosed in a
silken cocoon attached to the plant. The adult cabbage looper is grayish - brown
with a wingspread of about 1-1 /2 inches. A silvery white mark resembling a
"Figure 8" (that is open at the top) occurs on the middle of the front wing.
Biology
The adult moth lays 250 to 350 eggs that hatch in 2 to 3 days. These small
worms (small loopers) feed entirely upon foliage for 14 to 28 days, then pupate.
In 12 to 14 days an adult moth emerges from the pupae. A generation is completed
in about 35 days. In addition to cotton, cabbage looper larvae feed upon
numerous other plants including soybean, cabbage, tomato, several other
vegetables, and ornamental plants. Cabbage loopers are controlled by many
natural agents but especially by a virus that causes high larval mortality.
Damage
Cabbage looper larvae damage cotton by feeding on the leaves. They eat the
leaf area between the leaf veins leaving the leaf with a net-like appearance.
Severe defoliation while there are numerous immature bolls in the field, reduces
yields significantly. However, feeding damage late in the season may not cause
any loss of yield.
Scouting
Damage from cabbage looper can be detected by watching for feeding damage
while walking cotton fields. Cabbage loopers are held in control by several
natural agents and seldom cause problems. When observed, they should be reported
according to the criteria described below.
None - No cabbage loopers present.
Light - An occasional cabbage looper present. Slight defoliation of
leaves is observed.
Medium - Several cabbage loopers observed on each plant with 10 to 20%
defoliation present.
Heavy - Many cabbage loopers found. Greater than 20% defoliation is
observed.
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