How to Manage Pests

UC Pest Management Guidelines

Cucurbits

Cabbage Looper

Scientific Name: Trichoplusia ni

(Reviewed 12/09, updated 6/12)

In this Guideline:


DESCRIPTION OF THE PEST

Cabbage loopers are green caterpillars with a narrow, white stripe along each side and several narrow lines down the back; they have a characteristic arch to their back as they crawl. Eggs are similar in appearance to corn earworm eggs, but flatter, and laid singly on the underside of leaves. Adult moths have brown, mottled forewings marked in the center with a small, silver figure eight.

DAMAGE

The cabbage looper can be a very damaging pest. Young larvae feed primarily on the underside of leaves, skeletonizing them. High populations may move to the fruit and feed on the fruit surface.

MANAGEMENT

Encourage biological control agents by using least-toxic pesticides to control other pests. Treatments may be warranted if loopers are numerous.

Biological Control

Cabbage looper has many natural enemies that frequently keep it below economic levels, unless they are killed by insecticide applications. Important parasitic wasps include the tiny egg parasite, Trichogramma pretiosum, and three wasps that attack the caterpillars (Hyposoter exiguae, Copidosoma truncatellum, and Microplitis brassicae). The tachinid fly, Voria ruralis, also attacks the caterpillar. In some areas, the nuclear polyhedrosis virus, an important biological control agent, occurs naturally in fields and kills loopers that it infects.

Organically Acceptable Methods

Biological control and sprays of Bacillus thuringiensis are acceptable to use in an organically certified crop.

Monitoring and Treatment Decisions

Monitor adult flights throughout the season with pheromone traps to determine when to begin looking for loopers and if a pesticide application should be considered.

  1. Set out first traps when seedlings emerge or just before transplanting. Replace trap bottoms monthly or when they become covered with debris.
  2. When increasing numbers of moths are found in the traps, indicating a flight peak, it is time to start monitoring crop foliage for eggs and small larvae. Continue to monitor through fruit development.
  3. Treatments are generally warranted if there are sufficient numbers of loopers that are easily found feeding on leaves.
Common name Amount per acre R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. SPINETORAM
  (Radiant SC) 5–10 fl oz 4 see comments
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: PHI for cucumbers is 1 day and for other cucurbits 3 days.
 
B. SPINOSAD
  (Entrust)# 1.25–2.5 oz 4 see comments
  (Success) 4–8 fl oz 4 see comments
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Time spray to target eggs at hatch or small larvae. Do not apply more than 9 oz Entrust or 29 fl oz of Success/acre/season. PHI for cucumbers is 1 day and for other cucurbits 3 days.
 
C. CHLORANTRANILIPROLE  
  (Coragen) 3.5–5 fl oz 4 1
  MODE OF ACTION GROUP NUMBER1: 28
         
D. METHOXYFENOZIDE
  (Intrepid 2F) 4–10 fl oz 4 3
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Time spray to target eggs and small larvae. Do not apply more than 4 applications/acre/season or spray at less than 7-day intervals.
 
E. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Apply when eggs start to hatch and larvae are small (early instars) and before significant crop damage occurs. To be effective, Bacillus thuringiensis must be applied to young larva in the 1st or 2nd instar. Choose one of the other materials listed if larger larvae are present. Larvae must be actively feeding to be affected. Repeat as necessary to maintain control.
 
F. INDOXACARB
  (Avaunt) 2.5–6.0 oz 12 3
  MODE OF ACTION GROUP NUMBER1: 22
 
G. CRYOLITE
(Kryocide 96W) 8–12 lb 12 see comments
  MODE OF ACTION GROUP NUMBER1: 9A
COMMENTS: Labeled for use on cucumber, squash, melons, and pumpkins. Can be applied as a spray or dust. Thorough coverage using ground equipment is necessary for adequate control. Do not apply immediately before harvest. Remove excess residues on edible portions by washing, brushing, or other effective means. Effectiveness of this material is lower than materials listed above. PHI is 7 days for summer squash and 14 days for winter squash, cucumber, melons, and pumpkins.
  . . . or . . .
  (Prokil Cryolite 96) 10–16 lb 12 see comments
  COMMENTS: Labeled for use on cantaloupe, squash, and watermelon. Applied as a spray. Thorough coverage using ground equipment is necessary for adequate control. Do not apply immediately before harvest. Remove excess residues on edible portions by washing, brushing, or other effective means. Effectiveness of this material is lower than materials listed above. PHI is 7 days for summer squash and 14 days for winter squash, cantaloupe, and watermelon.
 
H. METHOMYL*
  (Lannate 90) 0.5–1 lb 48 see comments
  (Lannate LV) 1.5–3 pt 48 see comments
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Labeled for use on cucumbers, melons, and summer squash. Highly toxic to bees. PHI is 1 day when 0.5 lb or less for 90SP or 1.5 pt or less for LV formulations is used; when more than 0.5 lb (90SP) or 1.5 pt (LV) is used, PHI is 3 days.
 
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action Group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.
# Acceptable for organically grown produce.
* Permit required from county agricultural commissioner for purchase or use.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cucurbits
UC ANR Publication 3445

Insects and Mites

  • E. T. Natwick, UC Cooperative Extension, Imperial County
  • J. J. Stapleton, UC IPM Program, Kearney Agricultultural Center, Parlier
  • C. S. Stoddard, UC Cooperative Extension, Merced & Madera counties
Acknowledgment for contributions to Insects and Mites:
  • R. L. Coviello, UC Cooperative Extension, Fresno County
  • L. D. Godfrey, Entomology, UC Davis
  • C. B. Fouche, UC Cooperative Extension, San Joaquin County
  • C. G. Summers, Entomology, UC Davis/Kearney Agricultural Center, Parlier
  • J. B. LeBoeuf, AgriData Sensing, Inc., Fresno
  • M. Murray, UC Cooperative Extension, Colusa/Glenn counties

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