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Species Page

cabbage looper

Trichoplusia ni
This information is part of a full datasheet available in the Crop Protection Compendium (CPC). Find out more information on how to access the CPC.
©CAB International. Published under a CC-BY-NC-SA 4.0 licence.

Distribution

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Extent
Invasive
Origin
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Host plants / species affected

Main hosts

show all species affected
Brassica
Brassica juncea var. juncea (Indian mustard)
Brassica napus var. napobrassica (swede)
Brassica napus var. napus (rape)
Brassica oleracea (cabbages, cauliflowers)
Brassica oleracea var. botrytis (cauliflower)
Brassica oleracea var. capitata (cabbage)
Brassica oleracea var. gemmifera (Brussels sprouts)
Brassica oleracea var. gongylodes (kohlrabi)
Brassica oleracea var. italica (broccoli)
Brassica oleracea var. viridis (collards)
Brassica rapa subsp. chinensis (Chinese cabbage)
Brassica rapa subsp. oleifera (turnip rape)
Brassica rapa subsp. pekinensis
Brassica rapa subsp. rapa (turnip)
Brassicaceae (cruciferous crops)
Cucurbitaceae (cucurbits)
Gossypium (cotton)
Solanum lycopersicum (tomato)
Spinacia oleracea (spinach)

List of symptoms / signs

Leaves - external feeding
Leaves - frass visible
Leaves - internal feeding
Leaves - shredding
Leaves - webbing
Whole plant - dwarfing
Whole plant - external feeding
Whole plant - frass visible
Whole plant - internal feeding
Whole plant - plant dead; dieback

Symptoms

Larvae feed primarily on leaves and cause irregular holes (Metcalf et al., 1962; Banham and Arrand, 1970). They may also bore into the heads of lettuce, cabbage and tomatoes. Plants should be inspected for leaf damage and the presence of frass.

Prevention and control

Introduction

Control of T. ni is best achieved by regular field monitoring, applying control measures only when needed. This helps avoid the overuse of insecticides and the potential for the build up of insecticide resistance. Sampling plans should be constructed according to distributional characteristics of the insects and linked to an economic injury level. Control is not often needed because of the abundance of natural enemies, so regular monitoring of natural enemies is also important. Treatment thresholds vary depending on the crop and location and growers are advised to contact their local extension service or a private consultant for treatment guidelines, including the products, which are registered in the area. Normally, spraying should not occur when there is less than one larva per five plants.

Biological Control

A large number of microorganisms have been isolated from T. ni in the field (see Ignoffo and Hostetter, 1984 for a comprehensive list). Commercial preparations of bacteria (Bacillus thuringienis) and fungi (Beauvaria bassiana) can be applied. In low-input situations where it is allowed, virus-infected insects can be reintroduced into the field. This is performed by collecting diseased insects, mixing them in a blender, filtering out large tissue masses and then spraying the virus particles back onto the field.

At least 68 parasitoid species have been recovered from field-collected T. ni (Martin et al., 1984). Although all stages except the adult are attacked by parasitoids, the Trichogrammatidae may hold particular promise as they kill eggs and prevent any subsequent damage by larvae. Parasitoids and predators can be either introduced into the system by initial releases of small numbers in the hope they will multiply, or through the use of mass rearing and supplementary releases. Parasitism and predation can also be enhanced by changes in cropping practices (for example, strip cropping). Biopesticides may also be used; in Trinidad, T. ni attacking cabbage have been controlled by the introduction of Cotesia marginiventris and the nuclear polyhedrosis virus of T. ni (Yaseen, 1978).

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:

Impact

T. ni populations can cause both severe yield and quality losses, especially under dry conditions. Under severe infestations in cabbage, no heads may be marketable at the end of the season.