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University
of Rhode Island GreenShare Factsheets
Cabbage
Looper Trichoplusia
ni
Lepidoptera: Noctuidae
Cabbage looper
larvae eat large, irregular holes in the outer leaves of cabbage
plants, sometimes eating into the heads of cabbages. Heavy infestations
often result in skeletonized plants, as all but the leaf veins are
usually eaten. Cabbage loopers can be responsible for reduced yields,
heads which fail to form, and the contamination of the edible
portions of the plants. Cabbage
looper larvae are light green and 40 mm (1 1/2 inch) long when
mature. Older larvae have thin white lines running the length
of each side.
Loopers get their name from their peculiar walking behavior. They
have three pairs of slender legs at the front of their body
and
three pairs of stout prolegs on the last 1/3 of the abdomen and
no appendages in between. They move by gripping with the front
legs
and dragging the back legs forwards while arching the back. They
then grip with the rear prolegs and push forward to straighten
the "loop." The cabbage looper moths are nocturnal and are
rarely seen during daylight hours. The moths are grayish brown
with a wingspan
of 40 mm (1 1/2 inch). The front wings are mottled brown with a
small silver figure-8-shaped spot near the center, while the
second
wing pair is uniformly brown.
Cabbage loopers overwinter as pupae attached to host plants and
other nearby objects. The adults emerge in the spring and lay several
hundred eggs singly on the upper surfaces of host plant leaves.
Larval development may be completed in two weeks if weather is favorable,
and the cabbage looper can have three or more generations per year
in the northern United States. -
Crop remains should be cleaned up immediately after harvest and
fields should be plowed under to destroy overwintering pupae. -
Weeds such as wild mustard, peppergrass and shepherd's purse can
serve as alternate hosts for cabbage loopers and should not be allowed
to grow in or near gardens and fields. -
Early planting may allow harvesting before damage
becomes significant. - Bacillus
thuringiensis, a bacterial pathogen of butterfly and moth larvae,
can effectively control the cabbage looper when applied weekly as
a dust. - Insecticides
are available for use in home gardens which, if used according to
label directions, provide effective control. Cabbage loopers display
a remarkable talent for avoiding insecticide-treated plant tissue--care
must be taken to treat plants thoroughly or the larvae may eat the
untreated portions of the plant. By
David Gadoury, David B. Wallace and Richard A. Casagrande. Revised
1999
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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