hymenopus coronata

Conrad Bérubé
island crop management
email: uc779(at)freenet.victoria.bc.ca

Insect info

aphid life cycle
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Cabbage Looper

Information on this page is derived from public domain documents published by the federal government of canada, the provincial government of British Columbia and information contributed on electronic discussion groups. Please bear in mind that any pesticides mentioned in these pages may no longer be recommended or registered for the indicated use — check with your local pesticide officer or regional agrologist for current info (you can use the provincial directory on the internet to search for those job titles or call Enquiry bc at 1 800 663-7867 for assistance). It is recommended that you use a search engine using the common name and/or scientific name of the organism(s) below, together with the name of your province, to find biology and management information relevant to your local conditions.

If you choose to use chemical controls remember to
always follow pesticide label instructions!

insects of economic importance in Canada and British Columbia



family: noctuidae
species: trichoplusia ni
common names: cabbage looper
hosts: cole crops
notes:


 

 

Cabbage Looper     Cabbage Looper

 

Cabbage Looper    Cabbage Looper


Agriculture and Agri-Food Canada Insect Identification Sheet No. 43 March 1981


Cabbage Looper

Trichoplusia ni (Hubner)

This species occurs wherever cabbage is grown in North America. It is often found on the same plants with the imported cabbageworm, Pieris (=Artogeia) rapae (L).

Damaged Cabbage Patch

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Injury:

The greenish larvae of the cabbage looper feed mainly on the leaves of cabbage plants, but they are also known to attack cauliflower, broccoli, brussels sprouts, turnip, lettuce, tomato, celery, spinach, rape and tobacco. In heavy infestations, as many as 25-30 larvae per cabbage head have been observed. Even in lighter infestations, the damage caused by the feeding larvae, or caterpillars, can stunt the growth of susceptible crops.


Life Injury:

The adult moth, which flies at night, has mottled brownish fore wings, each marked by a small silvery spot. The hind wings are pale brown to bronzy. The female lays up to 100 round, greenish white eggs on both surfaces of plant leaves. Eggs are laid singly during May or early June. After hatching, the larvae feed on the cabbage heads and when full grown, pupate in cocoons on various parts of the plants. The adults emerge in about 2 weeks. There may be as many as three generations each year. The insect in the pupal stage, but most infestations arise from adult moths migrating from the United States.

The cabbage looper is so named because the larva, with three pairs of legs near the head and three pairs of prolegs at the rear, crawls by doubling up to form a loop, then projecting the front end of the body forward.


Control:

The cabbage looper may be controlled by spraying or dusting with a residual insecticide or with Bacillus thuringiensis. Plant stalks remaining after the crop has been harvested should be destroyed and the field plowed. It may also be helpful to remove weeds on which the first generation of larvae can develop, e.g., shepherd's purse, wild mustard and peppergrass. Natural enemies of the cabbage looper also contribute to its control. These include a polyhedral virus and four species of parasitic insects.

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Cole Crops Monitoring:
by Conrad Berube

Take 15 paces then drop to take sample unless plants are particularly infested; inspect leaves for leps and aphids; 5% infestation is threshold for wooly aphid.

There are three generations per year of imported cabbage worm and diamond-back moth. Previous work on thresholds was done by Harcourt: .67 cabbage looper equivalents = 1 imported cabbage worm. 1 diamond-back moth = .2 cabbage looper equivalents.

The idea is to use one model unit to simplify threshold calculations — .75 cabbage looper equivalents/ plant (for at least fifty plants) is the threshold. Threshold for cabbage and cauliflower is .25 cabbage looper equivalents during the heading to harvest stage. The disadvantages are that all insects on a whole plant must be counted which requires basic identifying skills. Binomial model is presence/absence system that uses damage on plant as basic parameter (which has the advantages that less training is needed, less time to scout fields, more user-friendly). 303, 40-plant samples demonstrated that of 152 decision-events, in over 90% of cases the same decisions were reached using a 40% infestation threshold compared to .25 cabbage looper equivalents threshold. Further testing of the threshold criteria for both protocols revealed curves that were very similar and yields that exhibited no significant difference in harvest yields. There was a significant savings in labor in labor with presence/absence protocol (14 mins for 10 plants for cabbage looper equivalents model 8.7 minutes for binomial sampling). Diamond-back moth and imported cabbage worm have high potential for biocontrol through a conservation approach.

Dibema insularae is a very effective parasitoid for diamond-back moth.

Cotesia, Pteromalius glomeratus, and Copidosoma (a polyembryonic egg-pupal parasitoid) are part of an effective parasitoid guild of imported cabbage worm.

Trichogramma work on cabbage looper. A tachinid (Vorea boralis) pupates right on looper larva.

   
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Copyright © 2007 Conrad Bérubé, site design, concept and scripting. All rights reserved worldwide.
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